From b65df72dda7448fafdcbc756dab3d31916e2ff5b Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Date: Thu, 13 Mar 2025 22:52:15 +0100
Subject: [PATCH 13/17] avcodec/hqx: Simplify deriving AC table index
It can be simply encoded in the quant coefficients itself
as they are so small.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
libavcodec/hqx.c | 61 ++++++++++++++++++++++++------------------------
1 file changed, 30 insertions(+), 31 deletions(-)
diff --git a/libavcodec/hqx.c b/libavcodec/hqx.c
index 54a9870e11..2e9698ee6c 100644
--- a/libavcodec/hqx.c
+++ b/libavcodec/hqx.c
@@ -75,21 +75,27 @@ typedef struct HQXContext {
#define HQX_HEADER_SIZE 59
+#define AC_IDX(q) ((q) >= 128 ? HQX_AC_Q128 : (q) >= 64 ? HQX_AC_Q64 : \
+ (q) >= 32 ? HQX_AC_Q32 : (q) >= 16 ? HQX_AC_Q16 : \
+ (q) >= 8 ? HQX_AC_Q8 : HQX_AC_Q0)
+
/* macroblock selects a group of 4 possible quants and
* a block can use any of those four quantisers
* one column is powers of 2, the other one is powers of 2 * 3,
- * then there is the special one, powers of 2 * 5 */
-static const int hqx_quants[16][4] = {
- { 0x1, 0x2, 0x4, 0x8 }, { 0x1, 0x3, 0x6, 0xC },
- { 0x2, 0x4, 0x8, 0x10 }, { 0x3, 0x6, 0xC, 0x18 },
- { 0x4, 0x8, 0x10, 0x20 }, { 0x6, 0xC, 0x18, 0x30 },
- { 0x8, 0x10, 0x20, 0x40 },
- { 0xA, 0x14, 0x28, 0x50 },
- { 0xC, 0x18, 0x30, 0x60 },
- { 0x10, 0x20, 0x40, 0x80 }, { 0x18, 0x30, 0x60, 0xC0 },
- { 0x20, 0x40, 0x80, 0x100 }, { 0x30, 0x60, 0xC0, 0x180 },
- { 0x40, 0x80, 0x100, 0x200 }, { 0x60, 0xC0, 0x180, 0x300 },
- { 0x80, 0x100, 0x200, 0x400 }
+ * then there is the special one, powers of 2 * 5.
+ * We also encode the corresponding AC index in these tables in bits 29-31. */
+static const unsigned hqx_quants[16][4] = {
+#define Q(q) ((unsigned)AC_IDX(q) << 29 | (q))
+ { Q( 0x1), Q( 0x2), Q( 0x4), Q( 0x8) }, { Q( 0x1), Q( 0x3), Q( 0x6), Q( 0xC) },
+ { Q( 0x2), Q( 0x4), Q( 0x8), Q( 0x10) }, { Q( 0x3), Q( 0x6), Q( 0xC), Q( 0x18) },
+ { Q( 0x4), Q( 0x8), Q( 0x10), Q( 0x20) }, { Q( 0x6), Q( 0xC), Q( 0x18), Q( 0x30) },
+ { Q( 0x8), Q( 0x10), Q( 0x20), Q( 0x40) },
+ { Q(0xA), Q(0x14), Q(0x28), Q(0x50) },
+ { Q( 0xC), Q(0x18), Q( 0x30), Q( 0x60) },
+ { Q(0x10), Q( 0x20), Q( 0x40), Q( 0x80) }, { Q(0x18), Q(0x30), Q( 0x60), Q( 0xC0) },
+ { Q(0x20), Q( 0x40), Q( 0x80), Q(0x100) }, { Q(0x30), Q(0x60), Q( 0xC0), Q(0x180) },
+ { Q(0x40), Q( 0x80), Q(0x100), Q(0x200) }, { Q(0x60), Q(0xC0), Q(0x180), Q(0x300) },
+ { Q(0x80), Q(0x100), Q(0x200), Q(0x400) }
};
static const uint8_t hqx_quant_luma[64] = {
@@ -143,12 +149,12 @@ static inline void hqx_get_ac(GetBitContext *gb, const HQXAC *ac,
}
static int decode_block(GetBitContext *gb, const VLCElem vlc[],
- const int *quants, int dcb,
+ const unsigned *quants, int dcb,
int16_t block[64], int *last_dc)
{
- int q, dc;
- int ac_idx;
int run, lev, pos = 0;
+ unsigned ac_idx, q;
+ int dc;
dc = get_vlc2(gb, vlc, HQX_DC_VLC_BITS, 2);
*last_dc += dc;
@@ -156,18 +162,9 @@ static int decode_block(GetBitContext *gb, const VLCElem vlc[],
block[0] = sign_extend(*last_dc << (12 - dcb), 12);
q = quants[get_bits(gb, 2)];
- if (q >= 128)
- ac_idx = HQX_AC_Q128;
- else if (q >= 64)
- ac_idx = HQX_AC_Q64;
- else if (q >= 32)
- ac_idx = HQX_AC_Q32;
- else if (q >= 16)
- ac_idx = HQX_AC_Q16;
- else if (q >= 8)
- ac_idx = HQX_AC_Q8;
- else
- ac_idx = HQX_AC_Q0;
+ // ac_idx is encoded in the high bits of quants;
+ // because block is 16 bit, we do not even need to clear said bits.
+ ac_idx = q >> 29;
do {
hqx_get_ac(gb, &hqx_ac[ac_idx], &run, &lev);
@@ -184,7 +181,7 @@ static int hqx_decode_422(HQXContext *ctx, int slice_no, int x, int y)
{
HQXSlice *slice = &ctx->slice[slice_no];
GetBitContext *gb = &slice->gb;
- const int *quants;
+ const unsigned *quants;
int flag;
int last_dc;
int i, ret;
@@ -219,7 +216,6 @@ static int hqx_decode_422a(HQXContext *ctx, int slice_no, int x, int y)
{
HQXSlice *slice = &ctx->slice[slice_no];
GetBitContext *gb = &slice->gb;
- const int *quants;
int flag = 0;
int last_dc;
int i, ret;
@@ -231,6 +227,8 @@ static int hqx_decode_422a(HQXContext *ctx, int slice_no, int x, int y)
cbp = get_vlc2(gb, cbp_vlc, HQX_CBP_VLC_BITS, 1);
if (cbp) {
+ const unsigned *quants;
+
if (ctx->interlaced)
flag = get_bits1(gb);
@@ -267,7 +265,7 @@ static int hqx_decode_444(HQXContext *ctx, int slice_no, int x, int y)
{
HQXSlice *slice = &ctx->slice[slice_no];
GetBitContext *gb = &slice->gb;
- const int *quants;
+ const unsigned *quants;
int flag;
int last_dc;
int i, ret;
@@ -304,7 +302,6 @@ static int hqx_decode_444a(HQXContext *ctx, int slice_no, int x, int y)
{
HQXSlice *slice = &ctx->slice[slice_no];
GetBitContext *gb = &slice->gb;
- const int *quants;
int flag = 0;
int last_dc;
int i, ret;
@@ -316,6 +313,8 @@ static int hqx_decode_444a(HQXContext *ctx, int slice_no, int x, int y)
cbp = get_vlc2(gb, cbp_vlc, HQX_CBP_VLC_BITS, 1);
if (cbp) {
+ const unsigned *quants;
+
if (ctx->interlaced)
flag = get_bits1(gb);
--
2.45.2