| Message ID | 20180108232739.24962-4-lorusak@gmail.com |
|---|---|
| State | New |
| Headers | show |
On Mon, 8 Jan 2018 15:27:39 -0800 Lukas Rusak <lorusak@gmail.com> wrote: > This default time base should be set in order for ffmpeg to rescale the timebase in v4l2_get_pts and v4l2_set_pts > > --- > libavcodec/v4l2_m2m_dec.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c > index 8308613978..4de091a011 100644 > --- a/libavcodec/v4l2_m2m_dec.c > +++ b/libavcodec/v4l2_m2m_dec.c > @@ -177,6 +177,8 @@ static av_cold int v4l2_decode_init(AVCodecContext *avctx) > capture->av_codec_id = AV_CODEC_ID_RAWVIDEO; > capture->av_pix_fmt = avctx->pix_fmt; > > + avctx->time_base = AV_TIME_BASE_Q; > + > ret = ff_v4l2_m2m_codec_init(avctx); > if (ret) { > av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n"); Decoders in FFmpeg don't really have a concept of a timebase. If they do, they should not use avctx->time_base, but avctx->pkt_timebase. (I don't think avctx->pkt_timebase even needs to be set - API users normally expect that the decoder simply passes through timestamps, regardless of timebase. But if pkt_timebase is set, it should be the same timebase that AVPacket uses, and the output AVFrames must use the same timebase. avctx->time_base doesn't really mean anything for decoding. There is an obscure "other" use of it that has been deprecated, and the replacement has the same obscure use (see doxygen).
I'm not really sure what to do then. Should I just replace time_base with pkt_timebase instead? Or Should I just remove the time base rescaling completely in v4l2_set_pts and v4l2_get_pts as it seems to be 1:1 anyways. On Mon, Jan 8, 2018 at 3:45 PM wm4 <nfxjfg@googlemail.com> wrote: > On Mon, 8 Jan 2018 15:27:39 -0800 > Lukas Rusak <lorusak@gmail.com> wrote: > > > This default time base should be set in order for ffmpeg to rescale the > timebase in v4l2_get_pts and v4l2_set_pts > > > > --- > > libavcodec/v4l2_m2m_dec.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c > > index 8308613978..4de091a011 100644 > > --- a/libavcodec/v4l2_m2m_dec.c > > +++ b/libavcodec/v4l2_m2m_dec.c > > @@ -177,6 +177,8 @@ static av_cold int v4l2_decode_init(AVCodecContext > *avctx) > > capture->av_codec_id = AV_CODEC_ID_RAWVIDEO; > > capture->av_pix_fmt = avctx->pix_fmt; > > > > + avctx->time_base = AV_TIME_BASE_Q; > > + > > ret = ff_v4l2_m2m_codec_init(avctx); > > if (ret) { > > av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n"); > > Decoders in FFmpeg don't really have a concept of a timebase. If they > do, they should not use avctx->time_base, but avctx->pkt_timebase. > > (I don't think avctx->pkt_timebase even needs to be set - API users > normally expect that the decoder simply passes through timestamps, > regardless of timebase. But if pkt_timebase is set, it should be the > same timebase that AVPacket uses, and the output AVFrames must use the > same timebase. > > avctx->time_base doesn't really mean anything for decoding. There is an > obscure "other" use of it that has been deprecated, and the replacement > has the same obscure use (see doxygen). > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel >
On Tue, 09 Jan 2018 00:03:15 +0000 Lukas Rusak <lorusak@gmail.com> wrote: > I'm not really sure what to do then. > > Should I just replace time_base with pkt_timebase instead? > > Or > > Should I just remove the time base rescaling completely in v4l2_set_pts and > v4l2_get_pts as it seems to be 1:1 anyways. The encoder needs to use time_base, the decoder pkt_timebase. If the decoder can simply pass through timestamps, you don't need to do any rescaling in the decoder. But I doubt v4l can do that.
diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c index 8308613978..4de091a011 100644 --- a/libavcodec/v4l2_m2m_dec.c +++ b/libavcodec/v4l2_m2m_dec.c @@ -177,6 +177,8 @@ static av_cold int v4l2_decode_init(AVCodecContext *avctx) capture->av_codec_id = AV_CODEC_ID_RAWVIDEO; capture->av_pix_fmt = avctx->pix_fmt; + avctx->time_base = AV_TIME_BASE_Q; + ret = ff_v4l2_m2m_codec_init(avctx); if (ret) { av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n");