On Thu, May 5, 2022 at 4:05 PM Guangyu Sun <sunguangy...@gmail.com> wrote:
> The decoded Data is not returned from the first frame; it must be used > to 'prime' the decode engine. The duration of the first packet should > be ignored also by the container, to make sure the total duration is > trimmed correctly. > > If the file has multiple pages for the data packets. The duration of the > last packet can be correctly adjusted without being affected by the first > packet. But if the first packet and the last packet are located in the > same page, the duration of the last packet will have an unwanted offset. > > This commit fixes https://trac.ffmpeg.org/ticket/6367. > > dd if=/dev/zero of=./silence.raw count=1 bs=500 > oggenc --raw silence.raw --output=silence.ogg > oggdec --raw --output silence.oggdec.raw silence.ogg > ffmpeg -codec:a libvorbis -i silence.ogg -f s16le -codec:a pcm_s16le > silence.libvorbis.ffmpeg.raw > ffmpeg -i silence.ogg -f s16le -codec:a pcm_s16le silence.native.ffmpeg.raw > ls -l *.raw > > Signed-off-by: Guangyu Sun <g...@roblox.com> > --- > libavformat/oggparsevorbis.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c > index 289900f7cf..9a486c9fe8 100644 > --- a/libavformat/oggparsevorbis.c > +++ b/libavformat/oggparsevorbis.c > @@ -412,6 +412,7 @@ static int vorbis_packet(AVFormatContext *s, int idx) > struct ogg_stream *os = ogg->streams + idx; > struct oggvorbis_private *priv = os->private; > int duration, flags = 0; > + int first_page; > > if (!priv->vp) > return AVERROR_INVALIDDATA; > @@ -420,7 +421,8 @@ static int vorbis_packet(AVFormatContext *s, int idx) > * here we parse the duration of each packet in the first page and > compare > * the total duration to the page granule to find the encoder delay > and > * set the first timestamp */ > - if ((!os->lastpts || os->lastpts == AV_NOPTS_VALUE) && !(os->flags & > OGG_FLAG_EOS) && (int64_t)os->granule>=0) { > + first_page = !os->lastpts || os->lastpts == AV_NOPTS_VALUE; > + if (first_page && !(os->flags & OGG_FLAG_EOS) && > (int64_t)os->granule>=0) { > int seg, d; > uint8_t *last_pkt = os->buf + os->pstart; > uint8_t *next_pkt = last_pkt; > @@ -479,6 +481,13 @@ static int vorbis_packet(AVFormatContext *s, int idx) > flags = 0; > } > os->pduration = duration; > + /* Data is not returned from the first frame; it must be used to > 'prime' > + * the decode engine. The duration of the first packet should be > ignored > + * also by the container, to make sure the total duration is > trimmed > + * correctly. > + */ > + if (first_page && os->segp == 1) > + os->pduration = 0; > } > > /* final packet handling > -- > 2.30.1 > > Ping. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
