[FFmpeg-devel] [PATCH v4] avcodec/v4l2_m2m: handle the v4l2 eos event

[Andriy Gelman]

On Wed, 01. Apr 10:38, Ming Qian wrote:
> when the last frame of capture is dequeueed,
> driver may send this V4L2_EVENT_EOS event,
> If this event is received, then the capture buffers have been flushed and
> avcodec_receive_packet()/avcodec_receive_frame() can return AVERROR_EOF.
> Otherwise, the draining continues until all the capture buffers have been dequeued or VIDIOC_DQBUF ioctl returns an EPIPE error.
> 
> Some devices may not support V4L2_EVENT_EOS.
> This is logged as a warning message and not treated as a fatal error during initialization.
> 
> Without this patch imx8qm often hangs at the end of encoding/decoding when
> flushing the capture buffers
> 
> Signed-off-by: Ming Qian <ming.qian at nxp.com>
> ---
>  libavcodec/v4l2_context.c |  6 ++++++
>  libavcodec/v4l2_m2m_dec.c |  8 ++++++++
>  libavcodec/v4l2_m2m_enc.c | 19 +++++++++++++++++++
>  3 files changed, 33 insertions(+)
> 
> diff --git a/libavcodec/v4l2_context.c b/libavcodec/v4l2_context.c
> index 8110bbb555..6b1f65fe4c 100644
> --- a/libavcodec/v4l2_context.c
> +++ b/libavcodec/v4l2_context.c
> @@ -154,6 +154,7 @@ static inline void v4l2_save_to_context(V4L2Context* ctx, struct v4l2_format_upd
>  }
>  
>  /**
> + * handle resolution change event and end of stream event
>   * returns 1 if reinit was successful, negative if it failed
>   * returns 0 if reinit was not executed
>   */
> @@ -171,6 +172,11 @@ static int v4l2_handle_event(V4L2Context *ctx)
>          return 0;
>      }
>  
> +    if (evt.type == V4L2_EVENT_EOS) {
> +        ctx->done = 1;
> +        return 0;
> +    }
> +
>      if (evt.type != V4L2_EVENT_SOURCE_CHANGE)
>          return 0;
>  
> diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c
> index d666edffe4..9989649784 100644
> --- a/libavcodec/v4l2_m2m_dec.c
> +++ b/libavcodec/v4l2_m2m_dec.c
> @@ -123,6 +123,14 @@ static int v4l2_prepare_decoder(V4L2m2mContext *s)
>          }
>      }
>  
> +    memset(&sub, 0, sizeof(sub));
> +    sub.type = V4L2_EVENT_EOS;
> +    ret = ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub);
> +    if (ret < 0) {
> +        av_log(s->avctx, AV_LOG_WARNING,
> +                "the v4l2 driver does not support end of stream VIDIOC_SUBSCRIBE_EVENT\n");
> +    }
> +
>      return 0;
>  }
>  
> diff --git a/libavcodec/v4l2_m2m_enc.c b/libavcodec/v4l2_m2m_enc.c
> index 84de63ec9d..78cf9ba47a 100644
> --- a/libavcodec/v4l2_m2m_enc.c
> +++ b/libavcodec/v4l2_m2m_enc.c
> @@ -155,6 +155,23 @@ static int v4l2_check_b_frame_support(V4L2m2mContext *s)
>      return AVERROR_PATCHWELCOME;
>  }
>  
> +static int v4l2_subscribe_eos_event(V4L2m2mContext *s)
> +{
> +    struct v4l2_event_subscription sub;
> +    int ret;
> +
> +    memset(&sub, 0, sizeof(sub));
> +    sub.type = V4L2_EVENT_EOS;
> +    ret = ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub);
> +    if (ret < 0) {
> +        av_log(s->avctx, AV_LOG_WARNING,
> +                "the v4l2 driver does not support end of stream VIDIOC_SUBSCRIBE_EVENT\n");
> +        return ret;
> +    }
> +
> +    return 0;
> +}
> +
>  static int v4l2_prepare_encoder(V4L2m2mContext *s)
>  {
>      AVCodecContext *avctx = s->avctx;
> @@ -164,6 +181,8 @@ static int v4l2_prepare_encoder(V4L2m2mContext *s)
>      /**
>       * requirements
>       */
> +    v4l2_subscribe_eos_event(s);
> +
>      ret = v4l2_check_b_frame_support(s);
>      if (ret)
>          return ret;
> -- 
> 2.26.0
> 

lgtm
Tested on RPi4 and Odroid XU4. 

Thanks,
-- 
Andriy