[FFmpeg-devel] [PATCH 6/7] matroskadec: read timecode in BlockAddition

[Jerome Martinez via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

[-- Attachment #1: 0006-matroskadec-read-timecode-in-BlockAddition.patch --]
[-- Type: text/plain, Size: 3448 bytes --]

>From 887508f9f4e4ab21431a41cc78bea48039811cba Mon Sep 17 00:00:00 2001
From: Jerome Martinez <jerome@mediaarea.net>
Date: Thu, 4 Sep 2025 20:17:55 +0200
Subject: [PATCH 6/7] matroskadec: read timecode in BlockAddition

---
 libavformat/matroska.h    |  1 +
 libavformat/matroskadec.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/libavformat/matroska.h b/libavformat/matroska.h
index 719f2ef796..d78b33d4b2 100644
--- a/libavformat/matroska.h
+++ b/libavformat/matroska.h
@@ -361,6 +361,7 @@ typedef enum {
   MATROSKA_BLOCK_ADD_ID_TYPE_DEFAULT                = 0,
   MATROSKA_BLOCK_ADD_ID_TYPE_OPAQUE                 = 1,
   MATROSKA_BLOCK_ADD_ID_TYPE_ITU_T_T35              = 4,
+  MATROSKA_BLOCK_ADD_ID_TYPE_SMPTE_12M              = 121,
   MATROSKA_BLOCK_ADD_ID_TYPE_DVCC                   = 0x64766343, // MKBETAG('d','v','c','C')
   MATROSKA_BLOCK_ADD_ID_TYPE_DVVC                   = 0x64767643, // MKBETAG('d','v','v','C')
 } MatroskaBlockAddIDType;
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 1e0c75c51b..d8800b48a6 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -295,6 +295,7 @@ typedef struct MatroskaTrack {
 
     uint32_t palette[AVPALETTE_COUNT];
     int has_palette;
+    int add_block_timecode_count;
 } MatroskaTrack;
 
 typedef struct MatroskaAttachment {
@@ -2530,6 +2531,9 @@ static int mkv_parse_block_addition_mappings(AVFormatContext *s, AVStream *st, M
                     return AVERROR_INVALIDDATA;
             }
             break;
+        case MATROSKA_BLOCK_ADD_ID_TYPE_SMPTE_12M:
+                track->add_block_timecode_count++;
+                break;
         case MATROSKA_BLOCK_ADD_ID_TYPE_DVCC:
         case MATROSKA_BLOCK_ADD_ID_TYPE_DVVC:
             if ((ret = mkv_parse_dvcc_dvvc(s, st, track, &mapping->extradata)) < 0)
@@ -3954,6 +3958,36 @@ static int matroska_parse_block_additional(MatroskaDemuxContext *matroska,
 
         return 0;
     }
+    case MATROSKA_BLOCK_ADD_ID_TYPE_SMPTE_12M: {
+        if (size < 8) {
+            av_log(matroska->ctx, AV_LOG_WARNING, "SMPTE timecode from BlockAdditional is malformed.\n");
+            break;
+        }
+
+        size_t sd_size = 0;
+        uint8_t *sd = av_packet_get_side_data(pkt, AV_PKT_DATA_S12M_TIMECODE, &sd_size);
+        uint64_t count = sd ? *((uint64_t*)sd) : 0;
+        if (!count) {
+            sd_size = sizeof(uint64_t) * (1 + track->add_block_timecode_count);
+            sd = av_packet_new_side_data(pkt, AV_PKT_DATA_S12M_TIMECODE, sd_size);
+            count = 0;
+        }
+
+        if (count >= track->add_block_timecode_count) {
+            av_log(matroska->ctx, AV_LOG_DEBUG, "There are more timecodes in the block than the count indicated in the track header, extra timecodes are ignored.\n");
+        }
+        else if (sd) {
+            uint64_t tc = *((uint64_t*)data);
+            av_log(matroska->ctx, AV_LOG_DEBUG, "Reading SMPTE timecode from BlockAdditional: 0x%016lX (RFC 5484)\n", tc);
+
+            uint64_t *sd_64 = (uint64_t*)sd;
+            count++;
+            *sd_64 = count;
+            AV_WB64(sd_64 + count, tc);
+        }
+        
+        return 0;
+    }
     default:
         break;
     }
-- 
2.46.0.windows.1

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