On Mon, 8 Jan 2018 15:27:39 -0800
Lukas Rusak <[email protected]> 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).
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