> -----Original Message-----
> From: Andriy Gelman [mailto:andriy.gel...@gmail.com]
> Sent: Monday, January 3, 2022 12:41 AM
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Cc: Ming Qian <ming.q...@nxp.com>
> Subject: [EXT] Re: [FFmpeg-devel] [PATCH v4 2/3] avcodec/v4l2_context:
> resume the decoding process after source change event received.
>
> Caution: EXT Email
>
> On Thu, 19. Aug 16:55, Ming Qian wrote:
> > client need to resume the decoding process after it dequeues the
> > source change event.
> > no matter what's the return value of v4l2_resolution_changed().
> > if the client doesn't resume the decoding process, the decoder may
> > keep waiting
> >
> > in documentation of v4l2 stateful decoder, we can see the following
> > description:
> > The client must continue the sequence as described below to
> > continue the decoding process.
> > 1. Dequeue the source change event.
> > Important
> > A source change triggers an implicit decoder drain,
> > similar to the explicit Drain sequence. The decoder is
> > stopped after it completes. The decoding process must be
> > resumed with either a pair of calls to
> > VIDIOC_STREAMOFF() and VIDIOC_STREAMON() on the
> CAPTURE
> > queue, or a call to VIDIOC_DECODER_CMD() with the
> > V4L2_DEC_CMD_START command.
> > 2. Continue with the Capture Setup sequence.
>
> Please also add that this fixes decoding of
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstreams
> .videolan.org%2Fffmpeg%2Fincoming%2F720p60.mp4&data=04%7C01%
> 7Cming.qian%40nxp.com%7Cea94a9c4cc0643b0a41f08d9ce0eadc5%7C686e
> a1d3bc2b4c6fa92cd99c5c301635%7C0%7C1%7C637767384703207931%7CU
> nknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6
> Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=X4rKQX19MQg1gO3ILiBCQ
> qSLIvqovZLA95KKiyoVNzI%3D&reserved=0 on RPi4.
>
Hi Andriy,
What's wrong with this stream? Everything is normal on my side when I play
it using ffplay.
> >
> > Signed-off-by: Ming Qian <ming.q...@nxp.com>
> > ---
> > libavcodec/v4l2_context.c | 52
> > ++++++++++++++++++++++++---------------
> > 1 file changed, 32 insertions(+), 20 deletions(-)
> >
> > diff --git a/libavcodec/v4l2_context.c b/libavcodec/v4l2_context.c
> > index dda5157698c3..b08f0015c2e5 100644
> > --- a/libavcodec/v4l2_context.c
> > +++ b/libavcodec/v4l2_context.c
> > @@ -153,6 +153,21 @@ static inline void
> v4l2_save_to_context(V4L2Context* ctx, struct v4l2_format_upd
> > }
> > }
> >
> > +static int v4l2_start_decode(V4L2Context *ctx) {
> > + struct v4l2_decoder_cmd cmd = {
> > + .cmd = V4L2_DEC_CMD_START,
> > + .flags = 0,
> > + };
> > + int ret;
> > +
> > + ret = ioctl(ctx_to_m2mctx(ctx)->fd, VIDIOC_DECODER_CMD, &cmd);
> > + if (ret)
> > + return AVERROR(errno);
> > +
> > + return 0;
> > +}
> > +
> > /**
> > * handle resolution change event and end of stream event
> > * returns 1 if reinit was successful, negative if it failed @@
> > -163,7 +178,7 @@ static int v4l2_handle_event(V4L2Context *ctx)
> > V4L2m2mContext *s = ctx_to_m2mctx(ctx);
> > struct v4l2_format cap_fmt = s->capture.format;
> > struct v4l2_event evt = { 0 };
> > - int reinit, ret;
> > + int ret;
> >
> > ret = ioctl(s->fd, VIDIOC_DQEVENT, &evt);
> > if (ret < 0) {
> > @@ -185,35 +200,29 @@ static int v4l2_handle_event(V4L2Context *ctx)
> > return 0;
> > }
> >
> > - reinit = v4l2_resolution_changed(&s->capture, &cap_fmt);
> > - if (reinit) {
> > + if (v4l2_resolution_changed(&s->capture, &cap_fmt)) {
> > s->capture.height = v4l2_get_height(&cap_fmt);
> > s->capture.width = v4l2_get_width(&cap_fmt);
> > s->capture.sample_aspect_ratio = v4l2_get_sar(&s->capture);
>
> > + } else {
> > + v4l2_start_decode(ctx);
> > + return 0;
> > }
>
> You can minimize the diff just by adding this part and the definition for
> v4l2_start_decode(). Then have a separate commit that cleans up and removes
> the reinit variable.
>
OK, I'll split it into two parts.
> >
> > - if (reinit)
> > - s->reinit = 1;
> > + s->reinit = 1;
> >
> > - if (reinit) {
> > - if (s->avctx)
> > - ret = ff_set_dimensions(s->avctx, s->capture.width,
> s->capture.height);
> > - if (ret < 0)
> > - av_log(logger(ctx), AV_LOG_WARNING, "update avcodec
> height and width\n");
> > + if (s->avctx)
> > + ret = ff_set_dimensions(s->avctx, s->capture.width,
> s->capture.height);
> > + if (ret < 0)
> > + av_log(logger(ctx), AV_LOG_WARNING, "update avcodec height
> > + and width\n");
> >
> > - ret = ff_v4l2_m2m_codec_reinit(s);
> > - if (ret) {
> > - av_log(logger(ctx), AV_LOG_ERROR,
> "v4l2_m2m_codec_reinit\n");
> > - return AVERROR(EINVAL);
> > - }
> > - goto reinit_run;
> > + ret = ff_v4l2_m2m_codec_reinit(s);
> > + if (ret) {
> > + av_log(logger(ctx), AV_LOG_ERROR, "v4l2_m2m_codec_reinit\n");
> > + return AVERROR(EINVAL);
> > }
> >
> > - /* dummy event received */
> > - return 0;
> > -
> > /* reinit executed */
> > -reinit_run:
> > return 1;
> > }
> >
> > @@ -551,6 +560,9 @@ int ff_v4l2_context_set_status(V4L2Context* ctx,
> uint32_t cmd)
> > int type = ctx->type;
> > int ret;
>
> >
> > + if (ctx->streamon == (cmd == VIDIOC_STREAMON))
> > + return 0;
> > +
>
> This change looks unrelated.
Yes it is not directly related, it's just an enhancement that avoid driver
can't handle the repeated streamon or streamoff ioctl.
Maybe I can remove it from this patch, and make a single patch.
>
> > ret = ioctl(ctx_to_m2mctx(ctx)->fd, cmd, &type);
> > if (ret < 0)
> > return AVERROR(errno);
>
> Thanks,
> --
> Andriy
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