[FFmpeg-devel] [PATCH 1/5] get_bits: move check_marker() to mpegvideodec.h

[FFmpeg-devel] [PATCH 1/5] get_bits: move check_marker() to mpegvideodec.h

[Anton Khirnov]

It is only used by mpegvideo-based decoders - specifically mpeg12, intelh263,
ituh263, mpeg4video.
---
 libavcodec/get_bits.h     | 10 ----------
 libavcodec/intelh263dec.c |  1 +
 libavcodec/ituh263dec.c   |  1 +
 libavcodec/mpegvideodec.h | 10 ++++++++++
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index d4e9276da1..498ce4ed35 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -610,16 +610,6 @@ static inline unsigned int show_bits_long(GetBitContext *s, int n)
     }
 }
 
-static inline int check_marker(void *logctx, GetBitContext *s, const char *msg)
-{
-    int bit = get_bits1(s);
-    if (!bit)
-        av_log(logctx, AV_LOG_INFO, "Marker bit missing at %d of %d %s\n",
-               get_bits_count(s) - 1, s->size_in_bits, msg);
-
-    return bit;
-}
-
 static inline int init_get_bits_xe(GetBitContext *s, const uint8_t *buffer,
                                    int bit_size, int is_le)
 {
diff --git a/libavcodec/intelh263dec.c b/libavcodec/intelh263dec.c
index e7e821d3b3..ded0a7f618 100644
--- a/libavcodec/intelh263dec.c
+++ b/libavcodec/intelh263dec.c
@@ -21,6 +21,7 @@
 #include "codec_internal.h"
 #include "mpegutils.h"
 #include "mpegvideo.h"
+#include "mpegvideodec.h"
 #include "h263data.h"
 #include "h263dec.h"
 #include "mpegvideodata.h"
diff --git a/libavcodec/ituh263dec.c b/libavcodec/ituh263dec.c
index f01c942f04..af054360d8 100644
--- a/libavcodec/ituh263dec.c
+++ b/libavcodec/ituh263dec.c
@@ -48,6 +48,7 @@
 #include "rv10dec.h"
 #include "mpeg4video.h"
 #include "mpegvideodata.h"
+#include "mpegvideodec.h"
 #include "mpeg4videodec.h"
 
 // The defines below define the number of bits that are read at once for
diff --git a/libavcodec/mpegvideodec.h b/libavcodec/mpegvideodec.h
index 1af8ebac36..10394a616c 100644
--- a/libavcodec/mpegvideodec.h
+++ b/libavcodec/mpegvideodec.h
@@ -67,4 +67,14 @@ static inline int mpeg_get_qscale(MpegEncContext *s)
         return qscale << 1;
 }
 
+static inline int check_marker(void *logctx, GetBitContext *s, const char *msg)
+{
+    int bit = get_bits1(s);
+    if (!bit)
+        av_log(logctx, AV_LOG_INFO, "Marker bit missing at %d of %d %s\n",
+               get_bits_count(s) - 1, s->size_in_bits, msg);
+
+    return bit;
+}
+
 #endif /* AVCODEC_MPEGVIDEODEC_H */
-- 
2.34.1

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[FFmpeg-devel] [PATCH 2/5] lavc: add standalone cached bitstream reader

[Anton Khirnov]

From: Alexandra Hájková <alexandra.khirnova@gmail.com>

The cached bitstream reader was originally written by Alexandra Hájková
for Libav, with significant input from Kostya Shishkov and Luca Barbato.
It was then committed to FFmpeg in ca079b09549, by merging it with the
implementation of the current bitstream reader.

This merge makes the code of get_bits.h significantly harder to read,
since it now contains two different bitstream readers interleaved with
 #ifdefs. Additionally, the code was committed without proper authorship
attribution.

This commit re-adds the cached bitstream reader as a standalone header,
as it was originally developed. It will be made useful in following
commits.

Integration by Anton Khirnov.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
---
 libavcodec/bitstream.h | 490 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 490 insertions(+)
 create mode 100644 libavcodec/bitstream.h

diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
new file mode 100644
index 0000000000..85f1af28c8
--- /dev/null
+++ b/libavcodec/bitstream.h
@@ -0,0 +1,490 @@
+/*
+ * Copyright (c) 2016 Alexandra Hájková
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * bitstream reader API header.
+ */
+
+#ifndef AVCODEC_BITSTREAM_H
+#define AVCODEC_BITSTREAM_H
+
+#include <stdint.h>
+
+#include "config.h"
+
+#include "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/log.h"
+
+#include "mathops.h"
+#include "vlc.h"
+
+#ifndef UNCHECKED_BITSTREAM_READER
+#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
+#endif
+
+typedef struct BitstreamContext {
+    uint64_t bits;      // stores bits read from the buffer
+    const uint8_t *buffer, *buffer_end;
+    const uint8_t *ptr; // pointer to the position inside a buffer
+    unsigned bits_left; // number of bits left in bits field
+    unsigned size_in_bits;
+} BitstreamContext;
+
+static inline void refill_64(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return;
+#endif
+
+#ifdef BITSTREAM_READER_LE
+    bc->bits       = AV_RL64(bc->ptr);
+#else
+    bc->bits       = AV_RB64(bc->ptr);
+#endif
+    bc->ptr       += 8;
+    bc->bits_left  = 64;
+}
+
+static inline void refill_32(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return;
+#endif
+
+#ifdef BITSTREAM_READER_LE
+    bc->bits       = (uint64_t)AV_RL32(bc->ptr) << bc->bits_left | bc->bits;
+#else
+    bc->bits       = bc->bits | (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_left);
+#endif
+    bc->ptr       += 4;
+    bc->bits_left += 32;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param bit_size the size of the buffer in bits
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
+ */
+static inline int bitstream_init(BitstreamContext *bc, const uint8_t *buffer,
+                                 unsigned int bit_size)
+{
+    unsigned int buffer_size;
+
+    if (bit_size > INT_MAX - 7 || !buffer) {
+        bc->buffer    = NULL;
+        bc->ptr       = NULL;
+        bc->bits_left = 0;
+        return AVERROR_INVALIDDATA;
+    }
+
+    buffer_size = (bit_size + 7) >> 3;
+
+    bc->buffer       = buffer;
+    bc->buffer_end   = buffer + buffer_size;
+    bc->ptr          = bc->buffer;
+    bc->size_in_bits = bit_size;
+    bc->bits_left    = 0;
+    bc->bits         = 0;
+
+    refill_64(bc);
+
+    return 0;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param byte_size the size of the buffer in bytes
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow
+ */
+static inline int bitstream_init8(BitstreamContext *bc, const uint8_t *buffer,
+                                  unsigned int byte_size)
+{
+    if (byte_size > INT_MAX / 8)
+        return AVERROR_INVALIDDATA;
+    return bitstream_init(bc, buffer, byte_size * 8);
+}
+
+/**
+ * Return number of bits already read.
+ */
+static inline int bitstream_tell(const BitstreamContext *bc)
+{
+    return (bc->ptr - bc->buffer) * 8 - bc->bits_left;
+}
+
+/**
+ * Return buffer size in bits.
+ */
+static inline int bitstream_tell_size(const BitstreamContext *bc)
+{
+    return bc->size_in_bits;
+}
+
+/**
+ * Return the number of the bits left in a buffer.
+ */
+static inline int bitstream_bits_left(const BitstreamContext *bc)
+{
+    return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_left;
+}
+
+static inline uint64_t get_val(BitstreamContext *bc, unsigned int n)
+{
+    uint64_t ret;
+
+#ifdef BITSTREAM_READER_LE
+    ret = bc->bits & ((UINT64_C(1) << n) - 1);
+    bc->bits >>= n;
+#else
+    ret = bc->bits >> (64 - n);
+    bc->bits <<= n;
+#endif
+    bc->bits_left -= n;
+
+    return ret;
+}
+
+/**
+ * Return one bit from the buffer.
+ */
+static inline unsigned int bitstream_read_bit(BitstreamContext *bc)
+{
+    if (!bc->bits_left)
+        refill_64(bc);
+
+    return get_val(bc, 1);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ */
+static inline uint64_t bitstream_read_63(BitstreamContext *bc, unsigned int n)
+{
+    uint64_t ret = 0;
+#ifdef BITSTREAM_READER_LE
+    uint64_t left = 0;
+#endif
+
+    if (!n)
+        return 0;
+
+    if (n > bc->bits_left) {
+        n -= bc->bits_left;
+#ifdef BITSTREAM_READER_LE
+        left = bc->bits_left;
+#endif
+        ret = get_val(bc, bc->bits_left);
+        refill_64(bc);
+    }
+
+#ifdef BITSTREAM_READER_LE
+    ret = get_val(bc, n) << left | ret;
+#else
+    ret = get_val(bc, n) | ret << n;
+#endif
+
+    return ret;
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-32  range.
+ */
+static inline uint32_t bitstream_read(BitstreamContext *bc, unsigned int n)
+{
+    if (!n)
+        return 0;
+
+    if (n > bc->bits_left) {
+        refill_32(bc);
+        if (bc->bits_left < 32)
+            bc->bits_left = n;
+    }
+
+    return get_val(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer.
+ * n has to be in the 0-32 range.
+ */
+static inline int32_t bitstream_read_signed(BitstreamContext *bc, unsigned int n)
+{
+    return sign_extend(bitstream_read(bc, n), n);
+}
+
+static inline unsigned int show_val(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_READER_LE
+    return bc->bits & ((UINT64_C(1) << n) - 1);
+#else
+    return bc->bits >> (64 - n);
+#endif
+}
+
+/**
+ * Return n bits from the buffer but do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline unsigned int bitstream_peek(BitstreamContext *bc, unsigned int n)
+{
+    if (n > bc->bits_left)
+        refill_32(bc);
+
+    return show_val(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer,
+ * do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline int bitstream_peek_signed(BitstreamContext *bc, unsigned int n)
+{
+    return sign_extend(bitstream_peek(bc, n), n);
+}
+
+static inline void skip_remaining(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_READER_LE
+    bc->bits >>= n;
+#else
+    bc->bits <<= n;
+#endif
+    bc->bits_left -= n;
+}
+
+/**
+ * Skip n bits in the buffer.
+ */
+static inline void bitstream_skip(BitstreamContext *bc, unsigned int n)
+{
+    if (n < bc->bits_left)
+        skip_remaining(bc, n);
+    else {
+        n -= bc->bits_left;
+        bc->bits      = 0;
+        bc->bits_left = 0;
+
+        if (n >= 64) {
+            unsigned int skip = n / 8;
+
+            n -= skip * 8;
+            bc->ptr += skip;
+        }
+        refill_64(bc);
+        if (n)
+            skip_remaining(bc, n);
+    }
+}
+
+/**
+ * Seek to the given bit position.
+ */
+static inline void bitstream_seek(BitstreamContext *bc, unsigned pos)
+{
+    bc->ptr       = bc->buffer;
+    bc->bits      = 0;
+    bc->bits_left = 0;
+
+    bitstream_skip(bc, pos);
+}
+
+/**
+ * Skip bits to a byte boundary.
+ */
+static inline const uint8_t *bitstream_align(BitstreamContext *bc)
+{
+    unsigned int n = -bitstream_tell(bc) & 7;
+    if (n)
+        bitstream_skip(bc, n);
+    return bc->buffer + (bitstream_tell(bc) >> 3);
+}
+
+/**
+ * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
+ * If MSB not set it is negative.
+ * @param n length in bits
+ */
+static inline int bitstream_read_xbits(BitstreamContext *bc, unsigned int n)
+{
+    int32_t cache = bitstream_peek(bc, 32);
+    int sign = ~cache >> 31;
+    skip_remaining(bc, n);
+
+    return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
+}
+
+/**
+ * Return decoded truncated unary code for the values 0, 1, 2.
+ */
+static inline int bitstream_decode012(BitstreamContext *bc)
+{
+    if (!bitstream_read_bit(bc))
+        return 0;
+    else
+        return bitstream_read_bit(bc) + 1;
+}
+
+/**
+ * Return decoded truncated unary code for the values 2, 1, 0.
+ */
+static inline int bitstream_decode210(BitstreamContext *bc)
+{
+    if (bitstream_read_bit(bc))
+        return 0;
+    else
+        return 2 - bitstream_read_bit(bc);
+}
+
+/* Read sign bit and flip the sign of the provided value accordingly. */
+static inline int bitstream_apply_sign(BitstreamContext *bc, int val)
+{
+    int sign = bitstream_read_signed(bc, 1);
+    return (val ^ sign) - sign;
+}
+
+static inline int bitstream_skip_1stop_8data(BitstreamContext *s)
+{
+    if (bitstream_bits_left(s) <= 0)
+        return AVERROR_INVALIDDATA;
+
+    while (bitstream_read(s, 1)) {
+        bitstream_skip(s, 8);
+        if (bitstream_bits_left(s) <= 0)
+            return AVERROR_INVALIDDATA;
+    }
+
+    return 0;
+}
+
+/* Unwind the cache so a refill_32 can fill it again. */
+static inline void bitstream_unwind(BitstreamContext *bc)
+{
+    int unwind = 4;
+    int unwind_bits = unwind * 8;
+
+    if (bc->bits_left < unwind_bits)
+        return;
+
+    bc->bits      >>= unwind_bits;
+    bc->bits      <<= unwind_bits;
+    bc->bits_left  -= unwind_bits;
+    bc->ptr        -= unwind;
+}
+
+/* Unget up to 32 bits. */
+static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
+                                   size_t amount)
+{
+    size_t cache_size = sizeof(bc->bits) * 8;
+
+    if (bc->bits_left + amount > cache_size)
+        bitstream_unwind(bc);
+
+    bc->bits       = (bc->bits >> amount) | (value << (cache_size - amount));
+    bc->bits_left += amount;
+}
+
+/**
+ * Return the LUT element for the given bitstream configuration.
+ */
+static inline int set_idx(BitstreamContext *bc, int code, int *n, int *nb_bits,
+                          VLC_TYPE (*table)[2])
+{
+    unsigned idx;
+
+    *nb_bits = -*n;
+    idx = bitstream_peek(bc, *nb_bits) + code;
+    *n = table[idx][1];
+
+    return table[idx][0];
+}
+
+/**
+ * Parse a vlc code.
+ * @param bits is the number of bits which will be read at once, must be
+ *             identical to nb_bits in init_vlc()
+ * @param max_depth is the number of times bits bits must be read to completely
+ *                  read the longest vlc code
+ *                  = (max_vlc_length + bits - 1) / bits
+ * If the vlc code is invalid and max_depth=1, then no bits will be removed.
+ * If the vlc code is invalid and max_depth>1, then the number of bits removed
+ * is undefined.
+ */
+static inline int bitstream_read_vlc(BitstreamContext *bc, VLC_TYPE (*table)[2],
+                                     int bits, int max_depth)
+{
+    int nb_bits;
+    unsigned idx = bitstream_peek(bc, bits);
+    int code     = table[idx][0];
+    int n        = table[idx][1];
+
+    if (max_depth > 1 && n < 0) {
+        skip_remaining(bc, bits);
+        code = set_idx(bc, code, &n, &nb_bits, table);
+        if (max_depth > 2 && n < 0) {
+            skip_remaining(bc, nb_bits);
+            code = set_idx(bc, code, &n, &nb_bits, table);
+        }
+    }
+    skip_remaining(bc, n);
+
+    return code;
+}
+
+#define BITSTREAM_RL_VLC(level, run, bc, table, bits, max_depth) \
+    do {                                                         \
+        int n, nb_bits;                                          \
+        unsigned int index = bitstream_peek(bc, bits);           \
+        level = table[index].level;                              \
+        n     = table[index].len;                                \
+                                                                 \
+        if (max_depth > 1 && n < 0) {                            \
+            bitstream_skip(bc, bits);                            \
+                                                                 \
+            nb_bits = -n;                                        \
+                                                                 \
+            index = bitstream_peek(bc, nb_bits) + level;         \
+            level = table[index].level;                          \
+            n     = table[index].len;                            \
+            if (max_depth > 2 && n < 0) {                        \
+                bitstream_skip(bc, nb_bits);                     \
+                nb_bits = -n;                                    \
+                                                                 \
+                index = bitstream_peek(bc, nb_bits) + level;     \
+                level = table[index].level;                      \
+                n     = table[index].len;                        \
+            }                                                    \
+        }                                                        \
+        run = table[index].run;                                  \
+        bitstream_skip(bc, n);                                   \
+    } while (0)
+
+#endif /* AVCODEC_BITSTREAM_H */
-- 
2.34.1

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[FFmpeg-devel] [PATCH 3/5] lavc/bitstream: templatize for BE/LE

[Anton Khirnov]

Allows using both BE and LE bitstream readers in the same file.
---
 libavcodec/bitstream.h          | 379 ++----------------------------
 libavcodec/bitstream_template.h | 392 ++++++++++++++++++++++++++++++++
 tests/ref/fate/source           |   1 +
 3 files changed, 415 insertions(+), 357 deletions(-)
 create mode 100644 libavcodec/bitstream_template.h

diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
index 85f1af28c8..3fa63695d3 100644
--- a/libavcodec/bitstream.h
+++ b/libavcodec/bitstream.h
@@ -49,88 +49,6 @@ typedef struct BitstreamContext {
     unsigned size_in_bits;
 } BitstreamContext;
 
-static inline void refill_64(BitstreamContext *bc)
-{
-#if !UNCHECKED_BITSTREAM_READER
-    if (bc->ptr >= bc->buffer_end)
-        return;
-#endif
-
-#ifdef BITSTREAM_READER_LE
-    bc->bits       = AV_RL64(bc->ptr);
-#else
-    bc->bits       = AV_RB64(bc->ptr);
-#endif
-    bc->ptr       += 8;
-    bc->bits_left  = 64;
-}
-
-static inline void refill_32(BitstreamContext *bc)
-{
-#if !UNCHECKED_BITSTREAM_READER
-    if (bc->ptr >= bc->buffer_end)
-        return;
-#endif
-
-#ifdef BITSTREAM_READER_LE
-    bc->bits       = (uint64_t)AV_RL32(bc->ptr) << bc->bits_left | bc->bits;
-#else
-    bc->bits       = bc->bits | (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_left);
-#endif
-    bc->ptr       += 4;
-    bc->bits_left += 32;
-}
-
-/**
- * Initialize BitstreamContext.
- * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
- *        larger than the actual read bits because some optimized bitstream
- *        readers read 32 or 64 bits at once and could read over the end
- * @param bit_size the size of the buffer in bits
- * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
- */
-static inline int bitstream_init(BitstreamContext *bc, const uint8_t *buffer,
-                                 unsigned int bit_size)
-{
-    unsigned int buffer_size;
-
-    if (bit_size > INT_MAX - 7 || !buffer) {
-        bc->buffer    = NULL;
-        bc->ptr       = NULL;
-        bc->bits_left = 0;
-        return AVERROR_INVALIDDATA;
-    }
-
-    buffer_size = (bit_size + 7) >> 3;
-
-    bc->buffer       = buffer;
-    bc->buffer_end   = buffer + buffer_size;
-    bc->ptr          = bc->buffer;
-    bc->size_in_bits = bit_size;
-    bc->bits_left    = 0;
-    bc->bits         = 0;
-
-    refill_64(bc);
-
-    return 0;
-}
-
-/**
- * Initialize BitstreamContext.
- * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
- *        larger than the actual read bits because some optimized bitstream
- *        readers read 32 or 64 bits at once and could read over the end
- * @param byte_size the size of the buffer in bytes
- * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow
- */
-static inline int bitstream_init8(BitstreamContext *bc, const uint8_t *buffer,
-                                  unsigned int byte_size)
-{
-    if (byte_size > INT_MAX / 8)
-        return AVERROR_INVALIDDATA;
-    return bitstream_init(bc, buffer, byte_size * 8);
-}
-
 /**
  * Return number of bits already read.
  */
@@ -155,235 +73,6 @@ static inline int bitstream_bits_left(const BitstreamContext *bc)
     return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_left;
 }
 
-static inline uint64_t get_val(BitstreamContext *bc, unsigned int n)
-{
-    uint64_t ret;
-
-#ifdef BITSTREAM_READER_LE
-    ret = bc->bits & ((UINT64_C(1) << n) - 1);
-    bc->bits >>= n;
-#else
-    ret = bc->bits >> (64 - n);
-    bc->bits <<= n;
-#endif
-    bc->bits_left -= n;
-
-    return ret;
-}
-
-/**
- * Return one bit from the buffer.
- */
-static inline unsigned int bitstream_read_bit(BitstreamContext *bc)
-{
-    if (!bc->bits_left)
-        refill_64(bc);
-
-    return get_val(bc, 1);
-}
-
-/**
- * Return n bits from the buffer, n has to be in the 0-63 range.
- */
-static inline uint64_t bitstream_read_63(BitstreamContext *bc, unsigned int n)
-{
-    uint64_t ret = 0;
-#ifdef BITSTREAM_READER_LE
-    uint64_t left = 0;
-#endif
-
-    if (!n)
-        return 0;
-
-    if (n > bc->bits_left) {
-        n -= bc->bits_left;
-#ifdef BITSTREAM_READER_LE
-        left = bc->bits_left;
-#endif
-        ret = get_val(bc, bc->bits_left);
-        refill_64(bc);
-    }
-
-#ifdef BITSTREAM_READER_LE
-    ret = get_val(bc, n) << left | ret;
-#else
-    ret = get_val(bc, n) | ret << n;
-#endif
-
-    return ret;
-}
-
-/**
- * Return n bits from the buffer, n has to be in the 0-32  range.
- */
-static inline uint32_t bitstream_read(BitstreamContext *bc, unsigned int n)
-{
-    if (!n)
-        return 0;
-
-    if (n > bc->bits_left) {
-        refill_32(bc);
-        if (bc->bits_left < 32)
-            bc->bits_left = n;
-    }
-
-    return get_val(bc, n);
-}
-
-/**
- * Return n bits from the buffer as a signed integer.
- * n has to be in the 0-32 range.
- */
-static inline int32_t bitstream_read_signed(BitstreamContext *bc, unsigned int n)
-{
-    return sign_extend(bitstream_read(bc, n), n);
-}
-
-static inline unsigned int show_val(BitstreamContext *bc, unsigned int n)
-{
-#ifdef BITSTREAM_READER_LE
-    return bc->bits & ((UINT64_C(1) << n) - 1);
-#else
-    return bc->bits >> (64 - n);
-#endif
-}
-
-/**
- * Return n bits from the buffer but do not change the buffer state.
- * n has to be in the 0-32 range.
- */
-static inline unsigned int bitstream_peek(BitstreamContext *bc, unsigned int n)
-{
-    if (n > bc->bits_left)
-        refill_32(bc);
-
-    return show_val(bc, n);
-}
-
-/**
- * Return n bits from the buffer as a signed integer,
- * do not change the buffer state.
- * n has to be in the 0-32 range.
- */
-static inline int bitstream_peek_signed(BitstreamContext *bc, unsigned int n)
-{
-    return sign_extend(bitstream_peek(bc, n), n);
-}
-
-static inline void skip_remaining(BitstreamContext *bc, unsigned int n)
-{
-#ifdef BITSTREAM_READER_LE
-    bc->bits >>= n;
-#else
-    bc->bits <<= n;
-#endif
-    bc->bits_left -= n;
-}
-
-/**
- * Skip n bits in the buffer.
- */
-static inline void bitstream_skip(BitstreamContext *bc, unsigned int n)
-{
-    if (n < bc->bits_left)
-        skip_remaining(bc, n);
-    else {
-        n -= bc->bits_left;
-        bc->bits      = 0;
-        bc->bits_left = 0;
-
-        if (n >= 64) {
-            unsigned int skip = n / 8;
-
-            n -= skip * 8;
-            bc->ptr += skip;
-        }
-        refill_64(bc);
-        if (n)
-            skip_remaining(bc, n);
-    }
-}
-
-/**
- * Seek to the given bit position.
- */
-static inline void bitstream_seek(BitstreamContext *bc, unsigned pos)
-{
-    bc->ptr       = bc->buffer;
-    bc->bits      = 0;
-    bc->bits_left = 0;
-
-    bitstream_skip(bc, pos);
-}
-
-/**
- * Skip bits to a byte boundary.
- */
-static inline const uint8_t *bitstream_align(BitstreamContext *bc)
-{
-    unsigned int n = -bitstream_tell(bc) & 7;
-    if (n)
-        bitstream_skip(bc, n);
-    return bc->buffer + (bitstream_tell(bc) >> 3);
-}
-
-/**
- * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
- * If MSB not set it is negative.
- * @param n length in bits
- */
-static inline int bitstream_read_xbits(BitstreamContext *bc, unsigned int n)
-{
-    int32_t cache = bitstream_peek(bc, 32);
-    int sign = ~cache >> 31;
-    skip_remaining(bc, n);
-
-    return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
-}
-
-/**
- * Return decoded truncated unary code for the values 0, 1, 2.
- */
-static inline int bitstream_decode012(BitstreamContext *bc)
-{
-    if (!bitstream_read_bit(bc))
-        return 0;
-    else
-        return bitstream_read_bit(bc) + 1;
-}
-
-/**
- * Return decoded truncated unary code for the values 2, 1, 0.
- */
-static inline int bitstream_decode210(BitstreamContext *bc)
-{
-    if (bitstream_read_bit(bc))
-        return 0;
-    else
-        return 2 - bitstream_read_bit(bc);
-}
-
-/* Read sign bit and flip the sign of the provided value accordingly. */
-static inline int bitstream_apply_sign(BitstreamContext *bc, int val)
-{
-    int sign = bitstream_read_signed(bc, 1);
-    return (val ^ sign) - sign;
-}
-
-static inline int bitstream_skip_1stop_8data(BitstreamContext *s)
-{
-    if (bitstream_bits_left(s) <= 0)
-        return AVERROR_INVALIDDATA;
-
-    while (bitstream_read(s, 1)) {
-        bitstream_skip(s, 8);
-        if (bitstream_bits_left(s) <= 0)
-            return AVERROR_INVALIDDATA;
-    }
-
-    return 0;
-}
-
 /* Unwind the cache so a refill_32 can fill it again. */
 static inline void bitstream_unwind(BitstreamContext *bc)
 {
@@ -412,52 +101,28 @@ static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
     bc->bits_left += amount;
 }
 
-/**
- * Return the LUT element for the given bitstream configuration.
- */
-static inline int set_idx(BitstreamContext *bc, int code, int *n, int *nb_bits,
-                          VLC_TYPE (*table)[2])
-{
-    unsigned idx;
-
-    *nb_bits = -*n;
-    idx = bitstream_peek(bc, *nb_bits) + code;
-    *n = table[idx][1];
-
-    return table[idx][0];
-}
-
-/**
- * Parse a vlc code.
- * @param bits is the number of bits which will be read at once, must be
- *             identical to nb_bits in init_vlc()
- * @param max_depth is the number of times bits bits must be read to completely
- *                  read the longest vlc code
- *                  = (max_vlc_length + bits - 1) / bits
- * If the vlc code is invalid and max_depth=1, then no bits will be removed.
- * If the vlc code is invalid and max_depth>1, then the number of bits removed
- * is undefined.
- */
-static inline int bitstream_read_vlc(BitstreamContext *bc, VLC_TYPE (*table)[2],
-                                     int bits, int max_depth)
-{
-    int nb_bits;
-    unsigned idx = bitstream_peek(bc, bits);
-    int code     = table[idx][0];
-    int n        = table[idx][1];
-
-    if (max_depth > 1 && n < 0) {
-        skip_remaining(bc, bits);
-        code = set_idx(bc, code, &n, &nb_bits, table);
-        if (max_depth > 2 && n < 0) {
-            skip_remaining(bc, nb_bits);
-            code = set_idx(bc, code, &n, &nb_bits, table);
-        }
-    }
-    skip_remaining(bc, n);
-
-    return code;
-}
+#define BITSTREAM_LE
+#include "bitstream_template.h"
+
+#undef BITSTREAM_LE
+#include "bitstream_template.h"
+
+#define bitstream_init          bitstream_init_be
+#define bitstream_init8         bitstream_init8_be
+#define bitstream_read_bit      bitstream_read_bit_be
+#define bitstream_read_63       bitstream_read_63_be
+#define bitstream_read          bitstream_read_be
+#define bitstream_read_signed   bitstream_read_signed_be
+#define bitstream_peek          bitstream_peek_be
+#define bitstream_peek_signed   bitstream_peek_signed_be
+#define bitstream_skip          bitstream_skip_be
+#define bitstream_seek          bitstream_seek_be
+#define bitstream_align         bitstream_align_be
+#define bitstream_read_xbits    bitstream_read_xbits_be
+#define bitstream_decode012     bitstream_decode012_be
+#define bitstream_decode210     bitstream_decode210_be
+#define bitstream_apply_sign    bitstream_apply_sign_be
+#define bitstream_read_vlc      bitstream_read_vlc_be
 
 #define BITSTREAM_RL_VLC(level, run, bc, table, bits, max_depth) \
     do {                                                         \
diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h
new file mode 100644
index 0000000000..14a420139c
--- /dev/null
+++ b/libavcodec/bitstream_template.h
@@ -0,0 +1,392 @@
+/*
+ * Copyright (c) 2016 Alexandra Hájková
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifdef BITSTREAM_LE
+#   define BS_SUFFIX le
+#else
+#   define BS_SUFFIX be
+#endif
+
+#define BS_JOIN(x, y) x ## _ ## y
+#define BS_FUNC2(x, y) BS_JOIN(x, y)
+#define BS_FUNC(x) BS_FUNC2(x, BS_SUFFIX)
+
+static inline void BS_FUNC(refill_64)(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return;
+#endif
+
+#ifdef BITSTREAM_LE
+    bc->bits       = AV_RL64(bc->ptr);
+#else
+    bc->bits       = AV_RB64(bc->ptr);
+#endif
+    bc->ptr       += 8;
+    bc->bits_left  = 64;
+}
+
+static inline void BS_FUNC(refill_32)(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return;
+#endif
+
+#ifdef BITSTREAM_LE
+    bc->bits       = (uint64_t)AV_RL32(bc->ptr) << bc->bits_left | bc->bits;
+#else
+    bc->bits       = bc->bits | (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_left);
+#endif
+    bc->ptr       += 4;
+    bc->bits_left += 32;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param bit_size the size of the buffer in bits
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
+ */
+static inline int BS_FUNC(bitstream_init)(BitstreamContext *bc, const uint8_t *buffer,
+                                          unsigned int bit_size)
+{
+    unsigned int buffer_size;
+
+    if (bit_size > INT_MAX - 7 || !buffer) {
+        bc->buffer    = NULL;
+        bc->ptr       = NULL;
+        bc->bits_left = 0;
+        return AVERROR_INVALIDDATA;
+    }
+
+    buffer_size = (bit_size + 7) >> 3;
+
+    bc->buffer       = buffer;
+    bc->buffer_end   = buffer + buffer_size;
+    bc->ptr          = bc->buffer;
+    bc->size_in_bits = bit_size;
+    bc->bits_left    = 0;
+    bc->bits         = 0;
+
+    BS_FUNC(refill_64)(bc);
+
+    return 0;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param byte_size the size of the buffer in bytes
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow
+ */
+static inline int BS_FUNC(bitstream_init8)(BitstreamContext *bc, const uint8_t *buffer,
+                                           unsigned int byte_size)
+{
+    if (byte_size > INT_MAX / 8)
+        return AVERROR_INVALIDDATA;
+    return BS_FUNC(bitstream_init)(bc, buffer, byte_size * 8);
+}
+
+static inline uint64_t BS_FUNC(get_val)(BitstreamContext *bc, unsigned int n)
+{
+    uint64_t ret;
+
+#ifdef BITSTREAM_LE
+    ret = bc->bits & ((UINT64_C(1) << n) - 1);
+    bc->bits >>= n;
+#else
+    ret = bc->bits >> (64 - n);
+    bc->bits <<= n;
+#endif
+    bc->bits_left -= n;
+
+    return ret;
+}
+
+/**
+ * Return one bit from the buffer.
+ */
+static inline unsigned int BS_FUNC(bitstream_read_bit)(BitstreamContext *bc)
+{
+    if (!bc->bits_left)
+        BS_FUNC(refill_64)(bc);
+
+    return BS_FUNC(get_val)(bc, 1);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ */
+static inline uint64_t BS_FUNC(bitstream_read_63)(BitstreamContext *bc, unsigned int n)
+{
+    uint64_t ret = 0;
+#ifdef BITSTREAM_LE
+    uint64_t left = 0;
+#endif
+
+    if (!n)
+        return 0;
+
+    if (n > bc->bits_left) {
+        n -= bc->bits_left;
+#ifdef BITSTREAM_LE
+        left = bc->bits_left;
+#endif
+        ret = BS_FUNC(get_val)(bc, bc->bits_left);
+        BS_FUNC(refill_64)(bc);
+    }
+
+#ifdef BITSTREAM_LE
+    ret = get_val_le(bc, n) << left | ret;
+#else
+    ret = get_val_be(bc, n) | ret << n;
+#endif
+
+    return ret;
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-32  range.
+ */
+static inline uint32_t BS_FUNC(bitstream_read)(BitstreamContext *bc, unsigned int n)
+{
+    if (!n)
+        return 0;
+
+    if (n > bc->bits_left) {
+        BS_FUNC(refill_32)(bc);
+        if (bc->bits_left < 32)
+            bc->bits_left = n;
+    }
+
+    return BS_FUNC(get_val)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer.
+ * n has to be in the 0-32 range.
+ */
+static inline int32_t BS_FUNC(bitstream_read_signed)(BitstreamContext *bc, unsigned int n)
+{
+    return sign_extend(BS_FUNC(bitstream_read)(bc, n), n);
+}
+
+static inline unsigned int BS_FUNC(show_val)(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_LE
+    return bc->bits & ((UINT64_C(1) << n) - 1);
+#else
+    return bc->bits >> (64 - n);
+#endif
+}
+
+/**
+ * Return n bits from the buffer but do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline unsigned int BS_FUNC(bitstream_peek)(BitstreamContext *bc, unsigned int n)
+{
+    if (n > bc->bits_left)
+        BS_FUNC(refill_32)(bc);
+
+    return BS_FUNC(show_val)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer,
+ * do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline int BS_FUNC(bitstream_peek_signed)(BitstreamContext *bc, unsigned int n)
+{
+    return sign_extend(BS_FUNC(bitstream_peek)(bc, n), n);
+}
+
+static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_LE
+    bc->bits >>= n;
+#else
+    bc->bits <<= n;
+#endif
+    bc->bits_left -= n;
+}
+
+/**
+ * Skip n bits in the buffer.
+ */
+static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n)
+{
+    if (n < bc->bits_left)
+        BS_FUNC(skip_remaining)(bc, n);
+    else {
+        n -= bc->bits_left;
+        bc->bits      = 0;
+        bc->bits_left = 0;
+
+        if (n >= 64) {
+            unsigned int skip = n / 8;
+
+            n -= skip * 8;
+            bc->ptr += skip;
+        }
+        BS_FUNC(refill_64)(bc);
+        if (n)
+            BS_FUNC(skip_remaining)(bc, n);
+    }
+}
+
+/**
+ * Seek to the given bit position.
+ */
+static inline void BS_FUNC(bitstream_seek)(BitstreamContext *bc, unsigned pos)
+{
+    bc->ptr       = bc->buffer;
+    bc->bits      = 0;
+    bc->bits_left = 0;
+
+    BS_FUNC(bitstream_skip)(bc, pos);
+}
+
+/**
+ * Skip bits to a byte boundary.
+ */
+static inline const uint8_t *BS_FUNC(bitstream_align)(BitstreamContext *bc)
+{
+    unsigned int n = -bitstream_tell(bc) & 7;
+    if (n)
+        BS_FUNC(bitstream_skip)(bc, n);
+    return bc->buffer + (bitstream_tell(bc) >> 3);
+}
+
+/**
+ * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
+ * If MSB not set it is negative.
+ * @param n length in bits
+ */
+static inline int BS_FUNC(bitstream_read_xbits)(BitstreamContext *bc, unsigned int n)
+{
+    int32_t cache = BS_FUNC(bitstream_peek)(bc, 32);
+    int sign = ~cache >> 31;
+    BS_FUNC(skip_remaining)(bc, n);
+
+    return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
+}
+
+/**
+ * Return decoded truncated unary code for the values 0, 1, 2.
+ */
+static inline int BS_FUNC(bitstream_decode012)(BitstreamContext *bc)
+{
+    if (!BS_FUNC(bitstream_read_bit)(bc))
+        return 0;
+    else
+        return BS_FUNC(bitstream_read_bit)(bc) + 1;
+}
+
+/**
+ * Return decoded truncated unary code for the values 2, 1, 0.
+ */
+static inline int BS_FUNC(bitstream_decode210)(BitstreamContext *bc)
+{
+    if (BS_FUNC(bitstream_read_bit)(bc))
+        return 0;
+    else
+        return 2 - BS_FUNC(bitstream_read_bit)(bc);
+}
+
+/* Read sign bit and flip the sign of the provided value accordingly. */
+static inline int BS_FUNC(bitstream_apply_sign)(BitstreamContext *bc, int val)
+{
+    int sign = BS_FUNC(bitstream_read_signed)(bc, 1);
+    return (val ^ sign) - sign;
+}
+
+static inline int BS_FUNC(bitstream_skip_1stop_8data)(BitstreamContext *s)
+{
+    if (bitstream_bits_left(s) <= 0)
+        return AVERROR_INVALIDDATA;
+
+    while (BS_FUNC(bitstream_read)(s, 1)) {
+        BS_FUNC(bitstream_skip)(s, 8);
+        if (bitstream_bits_left(s) <= 0)
+            return AVERROR_INVALIDDATA;
+    }
+
+    return 0;
+}
+
+/**
+ * Return the LUT element for the given bitstream configuration.
+ */
+static inline int BS_FUNC(set_idx)(BitstreamContext *bc, int code, int *n, int *nb_bits,
+                                   VLC_TYPE (*table)[2])
+{
+    unsigned idx;
+
+    *nb_bits = -*n;
+    idx = BS_FUNC(bitstream_peek)(bc, *nb_bits) + code;
+    *n = table[idx][1];
+
+    return table[idx][0];
+}
+
+/**
+ * Parse a vlc code.
+ * @param bits is the number of bits which will be read at once, must be
+ *             identical to nb_bits in init_vlc()
+ * @param max_depth is the number of times bits bits must be read to completely
+ *                  read the longest vlc code
+ *                  = (max_vlc_length + bits - 1) / bits
+ * If the vlc code is invalid and max_depth=1, then no bits will be removed.
+ * If the vlc code is invalid and max_depth>1, then the number of bits removed
+ * is undefined.
+ */
+static inline int BS_FUNC(bitstream_read_vlc)(BitstreamContext *bc, VLC_TYPE (*table)[2],
+                                              int bits, int max_depth)
+{
+    int nb_bits;
+    unsigned idx = BS_FUNC(bitstream_peek)(bc, bits);
+    int code     = table[idx][0];
+    int n        = table[idx][1];
+
+    if (max_depth > 1 && n < 0) {
+        BS_FUNC(skip_remaining)(bc, bits);
+        code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
+        if (max_depth > 2 && n < 0) {
+            BS_FUNC(skip_remaining)(bc, nb_bits);
+            code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
+        }
+    }
+    BS_FUNC(skip_remaining)(bc, n);
+
+    return code;
+}
+
+#undef BS_FUNC
+#undef BS_FUNC2
+#undef BS_JOIN
+#undef BS_SUFFIX
diff --git a/tests/ref/fate/source b/tests/ref/fate/source
index 16ea7ef9c1..3b7ea9c379 100644
--- a/tests/ref/fate/source
+++ b/tests/ref/fate/source
@@ -21,6 +21,7 @@ Headers without standard inclusion guards:
 compat/djgpp/math.h
 compat/float/float.h
 compat/float/limits.h
+libavcodec/bitstream_template.h
 tools/decode_simple.h
 Use of av_clip() where av_clip_uintp2() could be used:
 Use of av_clip() where av_clip_intp2() could be used:
-- 
2.34.1

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[FFmpeg-devel] [PATCH 4/5] lavc/bitstream: make skip_remaining() public

[Anton Khirnov]

Also rename it to bitstream_skip_cache(), which is more descriptive and
follows the naming conventions of tis API.
---
 libavcodec/bitstream.h          |  1 +
 libavcodec/bitstream_template.h | 19 ++++++++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
index 3fa63695d3..364245453b 100644
--- a/libavcodec/bitstream.h
+++ b/libavcodec/bitstream.h
@@ -116,6 +116,7 @@ static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
 #define bitstream_peek          bitstream_peek_be
 #define bitstream_peek_signed   bitstream_peek_signed_be
 #define bitstream_skip          bitstream_skip_be
+#define bitstream_skip_cache    bitstream_skip_cache_be
 #define bitstream_seek          bitstream_seek_be
 #define bitstream_align         bitstream_align_be
 #define bitstream_read_xbits    bitstream_read_xbits_be
diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h
index 14a420139c..717473ca40 100644
--- a/libavcodec/bitstream_template.h
+++ b/libavcodec/bitstream_template.h
@@ -225,7 +225,12 @@ static inline int BS_FUNC(bitstream_peek_signed)(BitstreamContext *bc, unsigned
     return sign_extend(BS_FUNC(bitstream_peek)(bc, n), n);
 }
 
-static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n)
+/**
+ * Skip n bits from the cache. This may only be called if at least n bits are
+ * guaranteed to be in the cache, e.g. right after bitstream_peek(n).
+ * Otherwise use bitstream_skip().
+ */
+static inline void BS_FUNC(bitstream_skip_cache)(BitstreamContext *bc, unsigned int n)
 {
 #ifdef BITSTREAM_LE
     bc->bits >>= n;
@@ -241,7 +246,7 @@ static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n)
 static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n)
 {
     if (n < bc->bits_left)
-        BS_FUNC(skip_remaining)(bc, n);
+        BS_FUNC(bitstream_skip_cache)(bc, n);
     else {
         n -= bc->bits_left;
         bc->bits      = 0;
@@ -255,7 +260,7 @@ static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n)
         }
         BS_FUNC(refill_64)(bc);
         if (n)
-            BS_FUNC(skip_remaining)(bc, n);
+            BS_FUNC(bitstream_skip_cache)(bc, n);
     }
 }
 
@@ -291,7 +296,7 @@ static inline int BS_FUNC(bitstream_read_xbits)(BitstreamContext *bc, unsigned i
 {
     int32_t cache = BS_FUNC(bitstream_peek)(bc, 32);
     int sign = ~cache >> 31;
-    BS_FUNC(skip_remaining)(bc, n);
+    BS_FUNC(bitstream_skip_cache)(bc, n);
 
     return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
 }
@@ -374,14 +379,14 @@ static inline int BS_FUNC(bitstream_read_vlc)(BitstreamContext *bc, VLC_TYPE (*t
     int n        = table[idx][1];
 
     if (max_depth > 1 && n < 0) {
-        BS_FUNC(skip_remaining)(bc, bits);
+        BS_FUNC(bitstream_skip_cache)(bc, bits);
         code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
         if (max_depth > 2 && n < 0) {
-            BS_FUNC(skip_remaining)(bc, nb_bits);
+            BS_FUNC(bitstream_skip_cache)(bc, nb_bits);
             code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
         }
     }
-    BS_FUNC(skip_remaining)(bc, n);
+    BS_FUNC(bitstream_skip_cache)(bc, n);
 
     return code;
 }
-- 
2.34.1

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[FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Anton Khirnov]

Use that instead of the merged version.
---
 libavcodec/get_bits.h | 296 +++++++-----------------------------------
 1 file changed, 50 insertions(+), 246 deletions(-)

diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 498ce4ed35..06192a25a7 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -59,12 +59,43 @@
 #define CACHED_BITSTREAM_READER 0
 #endif
 
+#if CACHED_BITSTREAM_READER
+#include "bitstream.h"
+
+#define MIN_CACHE_BITS 64
+
+typedef BitstreamContext GetBitContext;
+
+#define get_bits_count      bitstream_tell
+#define get_bits_left       bitstream_bits_left
+#define skip_bits_long      bitstream_skip
+#define skip_bits           bitstream_skip
+#define get_bits            bitstream_read
+#define get_bitsz           bitstream_read
+#define get_bits_le         bitstream_read
+#define get_bits_long       bitstream_read
+#define get_bits64          bitstream_read_63
+#define get_xbits           bitstream_read_xbits
+#define get_sbits           bitstream_read_signed
+#define get_sbits_long      bitstream_read_signed
+#define show_bits           bitstream_peek
+#define show_bits_long      bitstream_peek
+#define init_get_bits       bitstream_init
+#define init_get_bits8      bitstream_init8
+#define init_get_bits8_le   bitstream_init8_le
+#define align_get_bits      bitstream_align
+#define get_vlc2            bitstream_read_vlc
+
+#define get_bits1(s)        bitstream_read(s, 1)
+#define show_bits1(s)       bitstream_peek(s, 1)
+#define skip_bits1(s)       bitstream_skip(s, 1)
+
+#define skip_1stop_8data_bits bitstream_skip_1stop_8data
+
+#else   // CACHED_BITSTREAM_READER
+
 typedef struct GetBitContext {
     const uint8_t *buffer, *buffer_end;
-#if CACHED_BITSTREAM_READER
-    uint64_t cache;
-    unsigned bits_left;
-#endif
     int index;
     int size_in_bits;
     int size_in_bits_plus8;
@@ -121,16 +152,12 @@ static inline unsigned int show_bits(GetBitContext *s, int n);
  * For examples see get_bits, show_bits, skip_bits, get_vlc.
  */
 
-#if CACHED_BITSTREAM_READER
-#   define MIN_CACHE_BITS 64
-#elif defined LONG_BITSTREAM_READER
+#if defined LONG_BITSTREAM_READER
 #   define MIN_CACHE_BITS 32
 #else
 #   define MIN_CACHE_BITS 25
 #endif
 
-#if !CACHED_BITSTREAM_READER
-
 #define OPEN_READER_NOSIZE(name, gb)            \
     unsigned int name ## _index = (gb)->index;  \
     unsigned int av_unused name ## _cache
@@ -215,73 +242,12 @@ static inline unsigned int show_bits(GetBitContext *s, int n);
 
 #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
 
-#endif
 
 static inline int get_bits_count(const GetBitContext *s)
 {
-#if CACHED_BITSTREAM_READER
-    return s->index - s->bits_left;
-#else
     return s->index;
-#endif
 }
 
-#if CACHED_BITSTREAM_READER
-static inline void refill_32(GetBitContext *s, int is_le)
-{
-#if !UNCHECKED_BITSTREAM_READER
-    if (s->index >> 3 >= s->buffer_end - s->buffer)
-        return;
-#endif
-
-    if (is_le)
-        s->cache = (uint64_t)AV_RL32(s->buffer + (s->index >> 3)) << s->bits_left | s->cache;
-    else
-        s->cache = s->cache | (uint64_t)AV_RB32(s->buffer + (s->index >> 3)) << (32 - s->bits_left);
-    s->index     += 32;
-    s->bits_left += 32;
-}
-
-static inline void refill_64(GetBitContext *s, int is_le)
-{
-#if !UNCHECKED_BITSTREAM_READER
-    if (s->index >> 3 >= s->buffer_end - s->buffer)
-        return;
-#endif
-
-    if (is_le)
-        s->cache = AV_RL64(s->buffer + (s->index >> 3));
-    else
-        s->cache = AV_RB64(s->buffer + (s->index >> 3));
-    s->index += 64;
-    s->bits_left = 64;
-}
-
-static inline uint64_t get_val(GetBitContext *s, unsigned n, int is_le)
-{
-    uint64_t ret;
-    av_assert2(n>0 && n<=63);
-    if (is_le) {
-        ret = s->cache & ((UINT64_C(1) << n) - 1);
-        s->cache >>= n;
-    } else {
-        ret = s->cache >> (64 - n);
-        s->cache <<= n;
-    }
-    s->bits_left -= n;
-    return ret;
-}
-
-static inline unsigned show_val(const GetBitContext *s, unsigned n)
-{
-#ifdef BITSTREAM_READER_LE
-    return s->cache & ((UINT64_C(1) << n) - 1);
-#else
-    return s->cache >> (64 - n);
-#endif
-}
-#endif
-
 /**
  * Skips the specified number of bits.
  * @param n the number of bits to skip,
@@ -291,28 +257,12 @@ static inline unsigned show_val(const GetBitContext *s, unsigned n)
  */
 static inline void skip_bits_long(GetBitContext *s, int n)
 {
-#if CACHED_BITSTREAM_READER
-    skip_bits(s, n);
-#else
 #if UNCHECKED_BITSTREAM_READER
     s->index += n;
 #else
     s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
 #endif
-#endif
-}
-
-#if CACHED_BITSTREAM_READER
-static inline void skip_remaining(GetBitContext *s, unsigned n)
-{
-#ifdef BITSTREAM_READER_LE
-    s->cache >>= n;
-#else
-    s->cache <<= n;
-#endif
-    s->bits_left -= n;
 }
-#endif
 
 /**
  * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
@@ -321,13 +271,6 @@ static inline void skip_remaining(GetBitContext *s, unsigned n)
  */
 static inline int get_xbits(GetBitContext *s, int n)
 {
-#if CACHED_BITSTREAM_READER
-    int32_t cache = show_bits(s, 32);
-    int sign = ~cache >> 31;
-    skip_remaining(s, n);
-
-    return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
-#else
     register int sign;
     register int32_t cache;
     OPEN_READER(re, s);
@@ -338,10 +281,8 @@ static inline int get_xbits(GetBitContext *s, int n)
     LAST_SKIP_BITS(re, s, n);
     CLOSE_READER(re, s);
     return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
-#endif
 }
 
-#if !CACHED_BITSTREAM_READER
 static inline int get_xbits_le(GetBitContext *s, int n)
 {
     register int sign;
@@ -355,22 +296,16 @@ static inline int get_xbits_le(GetBitContext *s, int n)
     CLOSE_READER(re, s);
     return (zero_extend(sign ^ cache, n) ^ sign) - sign;
 }
-#endif
 
 static inline int get_sbits(GetBitContext *s, int n)
 {
     register int tmp;
-#if CACHED_BITSTREAM_READER
-    av_assert2(n>0 && n<=25);
-    tmp = sign_extend(get_bits(s, n), n);
-#else
     OPEN_READER(re, s);
     av_assert2(n>0 && n<=25);
     UPDATE_CACHE(re, s);
     tmp = SHOW_SBITS(re, s, n);
     LAST_SKIP_BITS(re, s, n);
     CLOSE_READER(re, s);
-#endif
     return tmp;
 }
 
@@ -380,32 +315,12 @@ static inline int get_sbits(GetBitContext *s, int n)
 static inline unsigned int get_bits(GetBitContext *s, int n)
 {
     register unsigned int tmp;
-#if CACHED_BITSTREAM_READER
-
-    av_assert2(n>0 && n<=32);
-    if (n > s->bits_left) {
-#ifdef BITSTREAM_READER_LE
-        refill_32(s, 1);
-#else
-        refill_32(s, 0);
-#endif
-        if (s->bits_left < 32)
-            s->bits_left = n;
-    }
-
-#ifdef BITSTREAM_READER_LE
-    tmp = get_val(s, n, 1);
-#else
-    tmp = get_val(s, n, 0);
-#endif
-#else
     OPEN_READER(re, s);
     av_assert2(n>0 && n<=25);
     UPDATE_CACHE(re, s);
     tmp = SHOW_UBITS(re, s, n);
     LAST_SKIP_BITS(re, s, n);
     CLOSE_READER(re, s);
-#endif
     av_assert2(tmp < UINT64_C(1) << n);
     return tmp;
 }
@@ -420,16 +335,6 @@ static av_always_inline int get_bitsz(GetBitContext *s, int n)
 
 static inline unsigned int get_bits_le(GetBitContext *s, int n)
 {
-#if CACHED_BITSTREAM_READER
-    av_assert2(n>0 && n<=32);
-    if (n > s->bits_left) {
-        refill_32(s, 1);
-        if (s->bits_left < 32)
-            s->bits_left = n;
-    }
-
-    return get_val(s, n, 1);
-#else
     register int tmp;
     OPEN_READER(re, s);
     av_assert2(n>0 && n<=25);
@@ -438,7 +343,6 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
     LAST_SKIP_BITS(re, s, n);
     CLOSE_READER(re, s);
     return tmp;
-#endif
 }
 
 /**
@@ -447,71 +351,22 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
 static inline unsigned int show_bits(GetBitContext *s, int n)
 {
     register unsigned int tmp;
-#if CACHED_BITSTREAM_READER
-    if (n > s->bits_left)
-#ifdef BITSTREAM_READER_LE
-        refill_32(s, 1);
-#else
-        refill_32(s, 0);
-#endif
-
-    tmp = show_val(s, n);
-#else
     OPEN_READER_NOSIZE(re, s);
     av_assert2(n>0 && n<=25);
     UPDATE_CACHE(re, s);
     tmp = SHOW_UBITS(re, s, n);
-#endif
     return tmp;
 }
 
 static inline void skip_bits(GetBitContext *s, int n)
 {
-#if CACHED_BITSTREAM_READER
-    if (n < s->bits_left)
-        skip_remaining(s, n);
-    else {
-        n -= s->bits_left;
-        s->cache = 0;
-        s->bits_left = 0;
-
-        if (n >= 64) {
-            unsigned skip = (n / 8) * 8;
-
-            n -= skip;
-            s->index += skip;
-        }
-#ifdef BITSTREAM_READER_LE
-        refill_64(s, 1);
-#else
-        refill_64(s, 0);
-#endif
-        if (n)
-            skip_remaining(s, n);
-    }
-#else
     OPEN_READER(re, s);
     LAST_SKIP_BITS(re, s, n);
     CLOSE_READER(re, s);
-#endif
 }
 
 static inline unsigned int get_bits1(GetBitContext *s)
 {
-#if CACHED_BITSTREAM_READER
-    if (!s->bits_left)
-#ifdef BITSTREAM_READER_LE
-        refill_64(s, 1);
-#else
-        refill_64(s, 0);
-#endif
-
-#ifdef BITSTREAM_READER_LE
-    return get_val(s, 1, 1);
-#else
-    return get_val(s, 1, 0);
-#endif
-#else
     unsigned int index = s->index;
     uint8_t result     = s->buffer[index >> 3];
 #ifdef BITSTREAM_READER_LE
@@ -528,7 +383,6 @@ static inline unsigned int get_bits1(GetBitContext *s)
     s->index = index;
 
     return result;
-#endif
 }
 
 static inline unsigned int show_bits1(GetBitContext *s)
@@ -549,10 +403,6 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
     av_assert2(n>=0 && n<=32);
     if (!n) {
         return 0;
-#if CACHED_BITSTREAM_READER
-    }
-    return get_bits(s, n);
-#else
     } else if (n <= MIN_CACHE_BITS) {
         return get_bits(s, n);
     } else {
@@ -564,7 +414,6 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
         return ret | get_bits(s, n - 16);
 #endif
     }
-#endif
 }
 
 /**
@@ -610,8 +459,17 @@ static inline unsigned int show_bits_long(GetBitContext *s, int n)
     }
 }
 
-static inline int init_get_bits_xe(GetBitContext *s, const uint8_t *buffer,
-                                   int bit_size, int is_le)
+
+/**
+ * Initialize GetBitContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bit at once and could read over the end
+ * @param bit_size the size of the buffer in bits
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
+ */
+static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
+                                int bit_size)
 {
     int buffer_size;
     int ret = 0;
@@ -630,33 +488,9 @@ static inline int init_get_bits_xe(GetBitContext *s, const uint8_t *buffer,
     s->buffer_end         = buffer + buffer_size;
     s->index              = 0;
 
-#if CACHED_BITSTREAM_READER
-    s->cache              = 0;
-    s->bits_left          = 0;
-    refill_64(s, is_le);
-#endif
-
     return ret;
 }
 
-/**
- * Initialize GetBitContext.
- * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
- *        larger than the actual read bits because some optimized bitstream
- *        readers read 32 or 64 bit at once and could read over the end
- * @param bit_size the size of the buffer in bits
- * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
- */
-static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
-                                int bit_size)
-{
-#ifdef BITSTREAM_READER_LE
-    return init_get_bits_xe(s, buffer, bit_size, 1);
-#else
-    return init_get_bits_xe(s, buffer, bit_size, 0);
-#endif
-}
-
 /**
  * Initialize GetBitContext.
  * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
@@ -678,7 +512,7 @@ static inline int init_get_bits8_le(GetBitContext *s, const uint8_t *buffer,
 {
     if (byte_size > INT_MAX / 8 || byte_size < 0)
         byte_size = -1;
-    return init_get_bits_xe(s, buffer, byte_size * 8, 1);
+    return init_get_bits(s, buffer, byte_size * 8);
 }
 
 static inline const uint8_t *align_get_bits(GetBitContext *s)
@@ -763,19 +597,6 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
         SKIP_BITS(name, gb, n);                                 \
     } while (0)
 
-/* Return the LUT element for the given bitstream configuration. */
-static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
-                          VLC_TYPE (*table)[2])
-{
-    unsigned idx;
-
-    *nb_bits = -*n;
-    idx = show_bits(s, *nb_bits) + code;
-    *n = table[idx][1];
-
-    return table[idx][0];
-}
-
 /**
  * Parse a vlc code.
  * @param bits is the number of bits which will be read at once, must be
@@ -788,24 +609,6 @@ static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
                                      int bits, int max_depth)
 {
-#if CACHED_BITSTREAM_READER
-    int nb_bits;
-    unsigned idx = show_bits(s, bits);
-    int code = table[idx][0];
-    int n    = table[idx][1];
-
-    if (max_depth > 1 && n < 0) {
-        skip_remaining(s, bits);
-        code = set_idx(s, code, &n, &nb_bits, table);
-        if (max_depth > 2 && n < 0) {
-            skip_remaining(s, nb_bits);
-            code = set_idx(s, code, &n, &nb_bits, table);
-        }
-    }
-    skip_remaining(s, n);
-
-    return code;
-#else
     int code;
 
     OPEN_READER(re, s);
@@ -816,7 +619,6 @@ static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
     CLOSE_READER(re, s);
 
     return code;
-#endif
 }
 
 static inline int decode012(GetBitContext *gb)
@@ -856,4 +658,6 @@ static inline int skip_1stop_8data_bits(GetBitContext *gb)
     return 0;
 }
 
+#endif // CACHED_BITSTREAM_READER
+
 #endif /* AVCODEC_GET_BITS_H */
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH 2/5] lavc: add standalone cached bitstream reader

[Paul B Mahol]

NAK
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[James Almer]

On 6/17/2022 12:00 PM, Paul B Mahol wrote:
> NAK

You'll have to give a reason for your NAK.
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Paul B Mahol]

NAK
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Paul B Mahol]

On Fri, Jun 17, 2022 at 5:01 PM James Almer <jamrial@gmail.com> wrote:

> On 6/17/2022 12:00 PM, Paul B Mahol wrote:
> > NAK
>
> You'll have to give a reason for your NAK.
>

Remove Alexandra from copyright from your refactoring of get_bits.h

And make sure changes are not making decoders slower than currently are.

> _______________________________________________
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>
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> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Jean-Baptiste Kempf]

On Fri, 17 Jun 2022, at 17:26, Paul B Mahol wrote:
> On Fri, Jun 17, 2022 at 5:01 PM James Almer <jamrial@gmail.com> wrote:
>
>> On 6/17/2022 12:00 PM, Paul B Mahol wrote:
>> > NAK
>>
>> You'll have to give a reason for your NAK.>

> Remove Alexandra from copyright from your refactoring of get_bits.h

Copyright does not work like that.

-- 
Jean-Baptiste Kempf -  President
+33 672 704 734
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Paul B Mahol]

On Sat, Jun 18, 2022 at 4:32 PM Jean-Baptiste Kempf <jb@videolan.org> wrote:

> On Fri, 17 Jun 2022, at 17:26, Paul B Mahol wrote:
> > On Fri, Jun 17, 2022 at 5:01 PM James Almer <jamrial@gmail.com> wrote:
> >
> >> On 6/17/2022 12:00 PM, Paul B Mahol wrote:
> >> > NAK
> >>
> >> You'll have to give a reason for your NAK.>
>
> > Remove Alexandra from copyright from your refactoring of get_bits.h
>
> Copyright does not work like that.
>


You are not the one who put that there.

I added her to that file, and due removal of her code from that file it is
no longer correct to keep it.

You are extremely biased and malice person, everybody can check this fact.



>
> --
> Jean-Baptiste Kempf -  President
> +33 672 704 734
> _______________________________________________
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Re: [FFmpeg-devel] [PATCH 4/5] lavc/bitstream: make skip_remaining() public

[Andreas Rheinhardt]

Anton Khirnov:
> Also rename it to bitstream_skip_cache(), which is more descriptive and
> follows the naming conventions of tis API.
> ---
>  libavcodec/bitstream.h          |  1 +
>  libavcodec/bitstream_template.h | 19 ++++++++++++-------
>  2 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
> index 3fa63695d3..364245453b 100644
> --- a/libavcodec/bitstream.h
> +++ b/libavcodec/bitstream.h
> @@ -116,6 +116,7 @@ static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
>  #define bitstream_peek          bitstream_peek_be
>  #define bitstream_peek_signed   bitstream_peek_signed_be
>  #define bitstream_skip          bitstream_skip_be
> +#define bitstream_skip_cache    bitstream_skip_cache_be
>  #define bitstream_seek          bitstream_seek_be
>  #define bitstream_align         bitstream_align_be
>  #define bitstream_read_xbits    bitstream_read_xbits_be
> diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h
> index 14a420139c..717473ca40 100644
> --- a/libavcodec/bitstream_template.h
> +++ b/libavcodec/bitstream_template.h
> @@ -225,7 +225,12 @@ static inline int BS_FUNC(bitstream_peek_signed)(BitstreamContext *bc, unsigned
>      return sign_extend(BS_FUNC(bitstream_peek)(bc, n), n);
>  }
>  
> -static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n)
> +/**
> + * Skip n bits from the cache. This may only be called if at least n bits are
> + * guaranteed to be in the cache, e.g. right after bitstream_peek(n).
> + * Otherwise use bitstream_skip().
> + */
> +static inline void BS_FUNC(bitstream_skip_cache)(BitstreamContext *bc, unsigned int n)
>  {
>  #ifdef BITSTREAM_LE
>      bc->bits >>= n;
> @@ -241,7 +246,7 @@ static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n)
>  static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n)
>  {
>      if (n < bc->bits_left)
> -        BS_FUNC(skip_remaining)(bc, n);
> +        BS_FUNC(bitstream_skip_cache)(bc, n);
>      else {
>          n -= bc->bits_left;
>          bc->bits      = 0;
> @@ -255,7 +260,7 @@ static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n)
>          }
>          BS_FUNC(refill_64)(bc);
>          if (n)
> -            BS_FUNC(skip_remaining)(bc, n);
> +            BS_FUNC(bitstream_skip_cache)(bc, n);
>      }
>  }
>  
> @@ -291,7 +296,7 @@ static inline int BS_FUNC(bitstream_read_xbits)(BitstreamContext *bc, unsigned i
>  {
>      int32_t cache = BS_FUNC(bitstream_peek)(bc, 32);
>      int sign = ~cache >> 31;
> -    BS_FUNC(skip_remaining)(bc, n);
> +    BS_FUNC(bitstream_skip_cache)(bc, n);
>  
>      return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
>  }
> @@ -374,14 +379,14 @@ static inline int BS_FUNC(bitstream_read_vlc)(BitstreamContext *bc, VLC_TYPE (*t
>      int n        = table[idx][1];
>  
>      if (max_depth > 1 && n < 0) {
> -        BS_FUNC(skip_remaining)(bc, bits);
> +        BS_FUNC(bitstream_skip_cache)(bc, bits);
>          code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
>          if (max_depth > 2 && n < 0) {
> -            BS_FUNC(skip_remaining)(bc, nb_bits);
> +            BS_FUNC(bitstream_skip_cache)(bc, nb_bits);
>              code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table);
>          }
>      }
> -    BS_FUNC(skip_remaining)(bc, n);
> +    BS_FUNC(bitstream_skip_cache)(bc, n);
>  
>      return code;
>  }

How do you intend to avoid the issue described here:
https://ffmpeg.org/pipermail/ffmpeg-devel/2022-June/297850.html?
Bitstream_peek() does not guarantee that there are bits bits in the
cache even though your documentation says otherwise.

- Andreas
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Anton Khirnov]

Quoting Paul B Mahol (2022-06-17 17:26:23)
> On Fri, Jun 17, 2022 at 5:01 PM James Almer <jamrial@gmail.com> wrote:
> 
> And make sure changes are not making decoders slower than currently are.

fraps
* before: 2.07428 +- 0.00101 seconds time elapsed
* after:  2.073444 +- 0.000678 seconds time elapsed
* -> same within 0.05%

magicyuv
* before: 1.65126 +- 0.00306 seconds time elapsed
* after:  1.64686 +- 0.00326 seconds time elapsed
* -> same within 0.3%

utvideo
* before: 1.364421 +- 0.000214 seconds time elapsed
* after: 1.364200 +- 0.000220 seconds time elapsed
* -> same within 0.02%

mvha, photocd, sheervideo: cannot test, no samples in FATE

-- 
Anton Khirnov
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Re: [FFmpeg-devel] [PATCH 5/5] lavc/get_bits: add a compat wrapper for the cached bitstream reader

[Anton Khirnov]

Quoting Jean-Baptiste Kempf (2022-06-18 16:31:55)
> On Fri, 17 Jun 2022, at 17:26, Paul B Mahol wrote:
> > On Fri, Jun 17, 2022 at 5:01 PM James Almer <jamrial@gmail.com> wrote:
> >
> >> On 6/17/2022 12:00 PM, Paul B Mahol wrote:
> >> > NAK
> >>
> >> You'll have to give a reason for your NAK.>
> 
> > Remove Alexandra from copyright from your refactoring of get_bits.h
> 
> Copyright does not work like that.

I see no problem with removing her - after this patch she really has no
code in that header.

-- 
Anton Khirnov
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