matroskadec: parse the channel layout mask for FLAC

It is commonly stored in a vorbiscomment block in codec private data.

1 files changed, 38 insertions, 0 deletions

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 2056391525..e376baeac2 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -55,6 +55,7 @@
 #include "internal.h"
 #include "isom.h"
 #include "matroska.h"
+#include "oggdec.h"
 /* For ff_codec_get_id(). */
 #include "riff.h"
 #include "rmsipr.h"
@@ -1443,6 +1444,7 @@ static int matroska_parse_flac(AVFormatContext *s,
                                MatroskaTrack *track,
                                int *offset)
 {
+    AVStream *st = track->stream;
     uint8_t *p = track->codec_priv.data;
     int size   = track->codec_priv.size;
 
@@ -1454,6 +1456,42 @@ static int matroska_parse_flac(AVFormatContext *s,
     *offset = 8;
     track->codec_priv.size = 8 + FLAC_STREAMINFO_SIZE;
 
+    p    += track->codec_priv.size;
+    size -= track->codec_priv.size;
+
+    /* parse the remaining metadata blocks if present */
+    while (size >= 4) {
+        int block_last, block_type, block_size;
+
+        flac_parse_block_header(p, &block_last, &block_type, &block_size);
+
+        p    += 4;
+        size -= 4;
+        if (block_size > size)
+            return 0;
+
+        /* check for the channel mask */
+        if (block_type == FLAC_METADATA_TYPE_VORBIS_COMMENT) {
+            AVDictionary *dict = NULL;
+            AVDictionaryEntry *chmask;
+
+            ff_vorbis_comment(s, &dict, p, block_size, 0);
+            chmask = av_dict_get(dict, "WAVEFORMATEXTENSIBLE_CHANNEL_MASK", NULL, 0);
+            if (chmask) {
+                uint64_t mask = strtol(chmask->value, NULL, 0);
+                if (!mask || mask & ~0x3ffffULL) {
+                    av_log(s, AV_LOG_WARNING,
+                           "Invalid value of WAVEFORMATEXTENSIBLE_CHANNEL_MASK\n");
+                } else
+                    st->codec->channel_layout = mask;
+            }
+            av_dict_free(&dict);
+        }
+
+        p    += block_size;
+        size -= block_size;
+    }
+
     return 0;
 }