Mkvtoolnix stores the sample rate of the original stream as reported by the "OpusHead" stream header instead of 48kHz, the actual sample rate of the Opus stream. Ignoring the stored sample rate and forcing 48kHz preserves the correct initial padding when remuxing.
Signed-off-by: James Almer <jamr...@gmail.com> --- OggOpus files created by opus-tools then remuxed into Matroska with mkvtoolnix results in files like the one mentioned above. See https://0x0.st/caG.mka or just use mkvtoolnix to remux fate-samples/ogg/intro-partial.opus Before this patch: $ mkvinfo caG.mka | grep delay | + Codec delay: 7.417ms (7416667ns) $ mkvinfo caG.mka | grep Sampling | + Sampling frequency: 44100 $ ffmpeg -v 0 -i caG.mka -c:a copy before.webm $ mkvinfo before.webm | grep delay | + Codec delay: 6.812ms (6812500ns) $ mkvinfo before.webm | grep Sampling | + Sampling frequency: 48000 Firefox can't play before.webm, but Opera (Chromium based) can. After this patch: $ ffmpeg -v 0 -i caG.mka -c:a copy after.webm $ mkvinfo after.webm | grep delay | + Codec delay: 7.417ms (7416667ns) $ mkvinfo after.webm | grep Sampling | + Sampling frequency: 48000 Both Firefox and Opera play after.webm I'm adding a check for Opus since I don't know when or if some other codec will use the codec_delay element in the future. At least for now it seems to be Opus exclusive. libavformat/matroskadec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c index 3270009..7880a10 100644 --- a/libavformat/matroskadec.c +++ b/libavformat/matroskadec.c @@ -2353,7 +2353,8 @@ static int matroska_parse_tracks(AVFormatContext *s) if (track->codec_delay > 0) { st->codecpar->initial_padding = av_rescale_q(track->codec_delay, (AVRational){1, 1000000000}, - (AVRational){1, st->codecpar->sample_rate}); + (AVRational){1, st->codecpar->codec_id == AV_CODEC_ID_OPUS ? + 48000 : st->codecpar->sample_rate}); } if (track->seek_preroll > 0) { st->codecpar->seek_preroll = av_rescale_q(track->seek_preroll, -- 2.8.2 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
