[FFmpeg-devel] [PATCH WIP 4/5] avcodec/hevc/sei: Add support for alpha channel information
Zhao Zhili
quinkblack at foxmail.com
Wed Dec 11 06:23:31 EET 2024
From: Zhao Zhili <zhilizhao at tencent.com>
---
libavcodec/hevc/sei.c | 30 ++++++++++++++++++++++++++++++
libavcodec/hevc/sei.h | 14 ++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/libavcodec/hevc/sei.c b/libavcodec/hevc/sei.c
index e11a33773c..56983fe96e 100644
--- a/libavcodec/hevc/sei.c
+++ b/libavcodec/hevc/sei.c
@@ -150,6 +150,34 @@ static int decode_nal_sei_timecode(HEVCSEITimeCode *s, GetBitContext *gb)
return 0;
}
+static int decode_nal_sei_alpha_info(HEVCSEIAlphaChannelInfo *s, GetBitContext *gb)
+{
+ int length;
+
+ s->has_alpha_channel_info = true;
+
+ s->alpha_channel_cancel_flag = get_bits1(gb);
+ if (!s->alpha_channel_cancel_flag) {
+ s->alpha_channel_use_idc = 2;
+ s->alpha_channel_incr_flag = 0;
+ s->alpha_channel_clip_flag = 0;
+
+ return 0;
+ }
+
+ s->alpha_channel_use_idc = get_bits(gb, 3);
+ s->alpha_channel_bit_depth_minus8 = get_bits(gb, 3);
+ length = s->alpha_channel_bit_depth_minus8 + 9;
+ s->alpha_transparent_value = get_bits(gb, length);
+ s->alpha_opaque_value = get_bits(gb, length);
+ s->alpha_channel_incr_flag = get_bits1(gb);
+ s->alpha_channel_clip_flag = get_bits1(gb);
+ if (s->alpha_channel_clip_flag)
+ s->alpha_channel_clip_type_flag = get_bits1(gb);
+
+ return 0;
+}
+
static int decode_nal_sei_3d_reference_displays_info(HEVCSEITDRDI *s, GetBitContext *gb)
{
s->prec_ref_display_width = get_ue_golomb(gb);
@@ -216,6 +244,8 @@ static int decode_nal_sei_prefix(GetBitContext *gb, GetByteContext *gbyte,
return decode_nal_sei_active_parameter_sets(s, gb, logctx);
case SEI_TYPE_TIME_CODE:
return decode_nal_sei_timecode(&s->timecode, gb);
+ case SEI_TYPE_ALPHA_CHANNEL_INFO:
+ return decode_nal_sei_alpha_info(&s->alpha, gb);
case SEI_TYPE_THREE_DIMENSIONAL_REFERENCE_DISPLAYS_INFO:
return decode_nal_sei_3d_reference_displays_info(&s->tdrdi, gb);
default: {
diff --git a/libavcodec/hevc/sei.h b/libavcodec/hevc/sei.h
index ee640003bc..54122c27df 100644
--- a/libavcodec/hevc/sei.h
+++ b/libavcodec/hevc/sei.h
@@ -21,6 +21,7 @@
#ifndef AVCODEC_HEVC_SEI_H
#define AVCODEC_HEVC_SEI_H
+#include <stdbool.h>
#include <stdint.h>
#include "libavutil/buffer.h"
@@ -95,6 +96,18 @@ typedef struct HEVCSEITDRDI {
uint8_t three_dimensional_reference_displays_extension_flag;
} HEVCSEITDRDI;
+typedef struct HEVCSEIAlphaChannelInfo {
+ bool has_alpha_channel_info;
+ uint8_t alpha_channel_cancel_flag;
+ uint8_t alpha_channel_use_idc;
+ uint8_t alpha_channel_bit_depth_minus8;
+ uint16_t alpha_transparent_value;
+ uint16_t alpha_opaque_value;
+ uint8_t alpha_channel_incr_flag;
+ uint8_t alpha_channel_clip_flag;
+ uint8_t alpha_channel_clip_type_flag;
+} HEVCSEIAlphaChannelInfo;
+
typedef struct HEVCSEI {
H2645SEI common;
HEVCSEIPictureHash picture_hash;
@@ -102,6 +115,7 @@ typedef struct HEVCSEI {
int active_seq_parameter_set_id;
HEVCSEITimeCode timecode;
HEVCSEITDRDI tdrdi;
+ HEVCSEIAlphaChannelInfo alpha;
} HEVCSEI;
struct HEVCParamSets;
--
2.46.0
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