On Tue, 14. Dec 02:12, Cameron Gutman wrote:
> The V4L2M2M API operates asynchronously, so multiple packets can
> be enqueued before getting a batch of frames back. Since it was
> only possible to receive a frame by submitting another packet,
> there wasn't a way to drain those excess output frames from when
> avcodec_receive_frame() returned AVERROR(EAGAIN).
>
> In my testing, this change reduced decode latency of a real-time
> 60 FPS H.264 stream by approximately 10x (200ms -> 20ms) on a
> Raspberry Pi 4.
>
> Signed-off-by: Cameron Gutman <aicomman...@gmail.com>
> ---
> libavcodec/v4l2_m2m_dec.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c
> index 224eb3d5e7..b0c3d30ac8 100644
> --- a/libavcodec/v4l2_m2m_dec.c
> +++ b/libavcodec/v4l2_m2m_dec.c
> @@ -142,8 +142,12 @@ static int v4l2_receive_frame(AVCodecContext *avctx,
> AVFrame *frame)
>
> if (!s->buf_pkt.size) {
> ret = ff_decode_get_packet(avctx, &s->buf_pkt);
> - if (ret < 0 && ret != AVERROR_EOF)
> - return ret;
> + if (ret < 0) {
> + if (ret == AVERROR(EAGAIN))
> + return ff_v4l2_context_dequeue_frame(capture, frame, 0);
> + else if (ret != AVERROR_EOF)
> + return ret;
> + }
> }
The change lgtm. I tested on Rpi4 and odroid xu4.
Will apply this on Sunday if no one else comments.
Thanks,
--
Andriy
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