[FFmpeg-devel] [PATCH] avformat/dashenc: add hevc codec attributes parse

* [FFmpeg-devel] [PATCH] avformat/dashenc: add hevc codec attributes parse
@ 2025-03-12  7:06 Jack Lau via ffmpeg-devel
  2025-03-27 12:47 ` Jack Lau
  2025-03-27 13:19 ` Zhao Zhili
  0 siblings, 2 replies; 3+ messages in thread
From: Jack Lau via ffmpeg-devel @ 2025-03-12  7:06 UTC (permalink / raw)
  To: ffmpeg-devel; +Cc: Jack Lau

fix ticket: 11316
add set_hevc_codec_str function refer to hlsenc.c but do some necessary changes
Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 libavformat/dashenc.c | 81 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
index d4a6fe0304..04c5b562d5 100644
--- a/libavformat/dashenc.c
+++ b/libavformat/dashenc.c
@@ -57,6 +57,7 @@
 #include "url.h"
 #include "vpcc.h"
 #include "dash.h"
+#include "nal.h"
 
 typedef enum {
     SEGMENT_TYPE_AUTO = 0,
@@ -344,6 +345,84 @@ static void set_vp9_codec_str(AVFormatContext *s, AVCodecParameters *par,
     return;
 }
 
+static void set_hevc_codec_str(AVCodecParameters *par, char *str, int size) {
+    uint8_t *data = par->extradata;
+    int profile = AV_PROFILE_UNKNOWN;
+    uint32_t profile_compatibility = AV_PROFILE_UNKNOWN; 
+    char tier = 0;
+    int level = AV_LEVEL_UNKNOWN;
+    char constraints[8] = "";
+
+    if (par->profile != AV_PROFILE_UNKNOWN)
+        profile = par->profile;
+    if (par->level != AV_LEVEL_UNKNOWN)
+        level = par->level;
+
+    /* check the boundary of data which from current position is small than extradata_size */
+    while (data && (data - par->extradata + 19) < par->extradata_size) {
+        /* get HEVC SPS NAL and seek to profile_tier_level */
+        if (!(data[0] | data[1] | data[2]) && data[3] == 1 && ((data[4] & 0x7E) == 0x42)) {
+            uint8_t *rbsp_buf;
+            int remain_size = 0;
+            int rbsp_size = 0;
+            uint32_t profile_compatibility_flags = 0;
+            uint8_t high_nibble = 0;
+            /* skip start code + nalu header */
+            data += 6;
+            /* process by reference General NAL unit syntax */
+            remain_size = par->extradata_size - (data - par->extradata);
+            rbsp_buf = ff_nal_unit_extract_rbsp(data, remain_size, &rbsp_size, 0);
+            if (!rbsp_buf)
+                return;
+            if (rbsp_size < 13) {
+                av_freep(&rbsp_buf);
+                break;
+            }
+            /* skip sps_video_parameter_set_id   u(4),
+            *      sps_max_sub_layers_minus1    u(3),
+            *  and sps_temporal_id_nesting_flag u(1) 
+            * 
+            * TIER represents the general_tier_flag, with 'L' indicating the flag is 0,
+            * and 'H' indicating the flag is 1
+            */
+            tier = (rbsp_buf[1] & 0x20) == 0 ? 'L' : 'H';
+            profile = rbsp_buf[1] & 0x1f;
+            /* PROFILE_COMPATIBILITY is general_profile_compatibility_flags, but in reverse bit order,
+            * in a hexadecimal representation (leading zeroes may be omitted).
+            */
+            profile_compatibility_flags = AV_RB32(rbsp_buf + 2);
+            /* revise these bits to get the profile compatibility value */
+            profile_compatibility_flags = ((profile_compatibility_flags & 0x55555555U) << 1) | ((profile_compatibility_flags >> 1) & 0x55555555U);
+            profile_compatibility_flags = ((profile_compatibility_flags & 0x33333333U) << 2) | ((profile_compatibility_flags >> 2) & 0x33333333U);
+            profile_compatibility_flags = ((profile_compatibility_flags & 0x0F0F0F0FU) << 4) | ((profile_compatibility_flags >> 4) & 0x0F0F0F0FU);
+            profile_compatibility_flags = ((profile_compatibility_flags & 0x00FF00FFU) << 8) | ((profile_compatibility_flags >> 8) & 0x00FF00FFU);
+            profile_compatibility = (profile_compatibility_flags << 16) | (profile_compatibility_flags >> 16);
+            /* skip 8 + 8 + 32
+            * CONSTRAINTS is a hexadecimal representation of the general_constraint_indicator_flags. 
+            * each byte is separated by a '.', and trailing zero bytes may be omitted.
+            * drop the trailing zero bytes refer to ISO/IEC14496-15.
+            */
+            high_nibble = rbsp_buf[7] >> 4;
+            snprintf(constraints, sizeof(constraints),
+                        high_nibble ? "%02x.%x" : "%02x",
+                        rbsp_buf[6], high_nibble);
+            /* skip 8 + 8 + 32 + 4 + 43 + 1 bit */
+            level = rbsp_buf[12];
+            av_freep(&rbsp_buf);
+            break;
+        }
+        data++;
+    }
+    if (profile != AV_PROFILE_UNKNOWN &&
+        profile_compatibility != AV_PROFILE_UNKNOWN &&
+        tier != 0 &&
+        level != AV_LEVEL_UNKNOWN &&
+        constraints[0] != '\0') {
+        av_strlcatf(str, size, ".%d.%x.%c%d.%s", profile, profile_compatibility, tier, level, constraints);
+    }
+    return;
+}
+
 static void set_codec_str(AVFormatContext *s, AVCodecParameters *par,
                           AVRational *frame_rate, char *str, int size)
 {
@@ -422,6 +501,8 @@ static void set_codec_str(AVFormatContext *s, AVCodecParameters *par,
             av_strlcatf(str, size, ".%02x%02x%02x",
                         extradata[1], extradata[2], extradata[3]);
         av_free(tmpbuf);
+    } else if (!strcmp(str, "hev1") || !strcmp(str, "hvc1")) {
+        set_hevc_codec_str(par, str, size);
     } else if (!strcmp(str, "av01")) {
         AV1SequenceParameters seq;
         if (!par->extradata_size)
-- 
2.47.1

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