[FFmpeg-devel] 回复: [EXT] Re: [PATCH] avcodec/v4l2_buffers: don't prevent enqueue capture buffer to driver

[Ming Qian]

Yes, I have meet some hang issue on nxp's imx platform.
On nxp's imx platform, there is a stream buffer in the v4l2 decoder driver.
So driver may cache some frames in driver, if without this patch, after the 
draining is set to 1, the v4l2 capture buffer won't be enqueued to driver any 
more, it leds to hang.

________________________________
发件人: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> 代表 Andriy Gelman 
<andriy.gel...@gmail.com>
发送时间: 2020年3月16日 20:07
收件人: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
主题: [EXT] Re: [FFmpeg-devel] [PATCH] avcodec/v4l2_buffers: don't prevent 
enqueue capture buffer to driver

Caution: EXT Email

On Mon, 16. Mar 10:02, Ming Qian wrote:
> the draining is set when the output port is finished,
> but it doesn't mean the capture port is finished.
> especially for decoder, there may be a stream buffer to store several
> frames.
> so the decoder still need capture buffer even if the draining is set.
>
> Signed-off-by: Ming Qian <ming.q...@nxp.com>
> ---
>  libavcodec/v4l2_buffers.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/v4l2_buffers.c b/libavcodec/v4l2_buffers.c
> index dc1b9eaf24..02f23d954b 100644
> --- a/libavcodec/v4l2_buffers.c
> +++ b/libavcodec/v4l2_buffers.c
> @@ -222,7 +222,7 @@ static void v4l2_free_buffer(void *opaque, uint8_t 
> *unused)
>              if (!atomic_load(&s->refcount))
>                  sem_post(&s->refsync);
>          } else {
> -            if (s->draining) {
> +            if (s->draining && V4L2_TYPE_IS_OUTPUT(avbuf->context->type)) {
>                  /* no need to queue more buffers to the driver */
>                  avbuf->status = V4L2BUF_AVAILABLE;
>              }

It makes sense, but did you have some dropped frames without this?

Thanks,
--
Andriy
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