[FFmpeg-devel] [PATCH] avcodec/vlc: auto calculate depth

[Paul B Mahol <onemda@gmail.com>]

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Patch attached.

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From e1ba15ab470752ebe937bc3865fb0dce99da1921 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Sat, 24 Jun 2023 10:02:35 +0200
Subject: [PATCH] libavcodec/vlc: auto calculate depth

Signed-off-by: Paul B Mahol <onemda@gmail.com>
---
 libavcodec/vlc.c | 9 +++++++--
 libavcodec/vlc.h | 1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/vlc.c b/libavcodec/vlc.c
index 96f2b28c7e..cfbf4717eb 100644
--- a/libavcodec/vlc.c
+++ b/libavcodec/vlc.c
@@ -276,7 +276,7 @@ int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
                        int flags)
 {
     VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
-    int j, ret;
+    int j, ret, max_len = 0;
 
     ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
     if (ret < 0)
@@ -296,6 +296,7 @@ int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
                 av_free(buf);                                               \
             return AVERROR(EINVAL);                                         \
         }                                                                   \
+        max_len = FFMAX(max_len, len);                                      \
         buf[j].bits = len;                                                  \
         GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);            \
         if (buf[j].code >= (1LL<<buf[j].bits)) {                            \
@@ -321,6 +322,7 @@ int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
     COPY(len && len <= nb_bits);
     nb_codes = j;
 
+    vlc->depth = (max_len + nb_bits - 1) / nb_bits;
     return vlc_common_end(vlc, nb_bits, nb_codes, buf,
                           flags, localbuf);
 }
@@ -332,7 +334,7 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
 {
     VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
     uint64_t code;
-    int ret, j, len_max = FFMIN(32, 3 * nb_bits);
+    int ret, j, len_max = FFMIN(32, 3 * nb_bits), max_len = 0;
 
     ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
     if (ret < 0)
@@ -344,6 +346,7 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
         if (len > 0) {
             unsigned sym;
 
+            max_len = FFMAX(max_len, len);
             buf[j].bits = len;
             if (symbols)
                 GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
@@ -353,6 +356,7 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
             buf[j++].code = code;
         } else if (len <  0) {
             len = -len;
+            max_len = FFMAX(max_len, len);
         } else
             continue;
         if (len > len_max || code & ((1U << (32 - len)) - 1)) {
@@ -365,6 +369,7 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
             goto fail;
         }
     }
+    vlc->depth = (max_len + nb_bits - 1) / nb_bits;
     return vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
 fail:
     if (buf != localbuf)
diff --git a/libavcodec/vlc.h b/libavcodec/vlc.h
index e63c484755..71127b0618 100644
--- a/libavcodec/vlc.h
+++ b/libavcodec/vlc.h
@@ -30,6 +30,7 @@ typedef struct VLCElem {
 
 typedef struct VLC {
     int bits;
+    int depth;
     VLCElem *table;
     int table_size, table_allocated;
 } VLC;
-- 
2.39.1


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