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avcodec/codec_internal: Use bitfield for alpha_modes

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Right now, FFCodec contains a dedicated pointer for
alpha_mode; this is wasteful, as there is only a very limited
range of options for this value, namely four.
So store it as a two-bit bitfield like color_ranges.
This reduces sizeof(FFCodec) by 16 here (the placement
of alpha_mode entailed unnecessary padding) and
saves 11328B of .data.rel.ro here (on a standard build with
no external libraries).

(If it were not for effective-type violations, one could
share the code and the table with AV_CODEC_CONFIG_COLOR_RANGE.)

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-11-03 08:22:59 +01:00
committed by James Almer
parent df1b6f9cfd
commit ab70751c8a
5 changed files with 35 additions and 27 deletions
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libavcodec/avcodec.c
+23 -6
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@@ -23,6 +23,8 @@
* AVCodecContext functions for libavcodec
*/
#include <assert.h>
#include "config.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
@@ -30,7 +32,6 @@
#include "libavutil/channel_layout.h"
#include "libavutil/common.h"
#include "libavutil/emms.h"
#include "libavutil/fifo.h"
#include "libavutil/imgutils.h"
#include "libavutil/mem.h"
#include "libavutil/opt.h"
@@ -41,12 +42,10 @@
#include "codec_desc.h"
#include "codec_internal.h"
#include "decode.h"
#include "encode.h"
#include "frame_thread_encoder.h"
#include "hwconfig.h"
#include "internal.h"
#include "libavutil/refstruct.h"
#include "thread.h"
/**
* Maximum size in bytes of extradata.
@@ -737,7 +736,17 @@ static const enum AVColorRange color_range_tab[] = {
AVCOL_RANGE_MPEG, AVCOL_RANGE_UNSPECIFIED,
};
static const uint8_t color_range_offsets[] = {
static const enum AVAlphaMode alpha_mode_tab[] = {
AVALPHA_MODE_PREMULTIPLIED, AVALPHA_MODE_STRAIGHT, AVALPHA_MODE_UNSPECIFIED,
AVALPHA_MODE_PREMULTIPLIED, AVALPHA_MODE_UNSPECIFIED
};
static_assert((int)AVCOL_RANGE_MPEG == (int)AVALPHA_MODE_PREMULTIPLIED, "unexpected enum values");
static_assert((int)AVCOL_RANGE_JPEG == (int)AVALPHA_MODE_STRAIGHT, "unexpected enum values");
static_assert(AVCOL_RANGE_UNSPECIFIED == 0 && AVALPHA_MODE_UNSPECIFIED == 0, "unexpected enum values");
static_assert(AVCOL_RANGE_NB == 3 && AVALPHA_MODE_NB == 3, "unexpected enum values");
static const uint8_t offset_tab[] = {
[AVCOL_RANGE_MPEG] = 3,
[AVCOL_RANGE_JPEG] = 1,
[AVCOL_RANGE_MPEG | AVCOL_RANGE_JPEG] = 0,
@@ -771,7 +780,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
return AVERROR(EINVAL);
unsigned color_ranges = codec2->color_ranges;
if (color_ranges)
*out_configs = color_range_tab + color_range_offsets[color_ranges];
*out_configs = color_range_tab + offset_tab[color_ranges];
else
*out_configs = NULL;
*out_num_configs = av_popcount(color_ranges);
@@ -783,7 +792,15 @@ FF_ENABLE_DEPRECATION_WARNINGS
return 0;
case AV_CODEC_CONFIG_ALPHA_MODE:
WRAP_CONFIG(AVMEDIA_TYPE_VIDEO, codec2->alpha_modes, enum AVAlphaMode, AVALPHA_MODE_UNSPECIFIED);
if (codec->type != AVMEDIA_TYPE_VIDEO)
return AVERROR(EINVAL);
unsigned alpha_modes = codec2->alpha_modes;
if (alpha_modes)
*out_configs = alpha_mode_tab + offset_tab[alpha_modes];
else
*out_configs = NULL;
*out_num_configs = av_popcount(alpha_modes);
return 0;
default:
return AVERROR(EINVAL);