Hi Ming, Sorry for the late reply.
On Tue, 29. Mar 06:51, Ming Qian wrote: > > From: Andriy Gelman [mailto:andriy.gel...@gmail.com] > > Sent: Saturday, March 26, 2022 11:43 PM > > To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> > > Cc: Ming Qian <ming.q...@nxp.com> > > Subject: Re: [FFmpeg-devel] [EXT] [PATCH v5 7/7] avcodec/v4l2_m2m_dec: > > setup capture queue before enqueue the first frame > > > > Caution: EXT Email > > > > Hi Ming, > > > > On Mon, 21. Mar 07:27, Ming Qian wrote: > > > Hi Andriy, > > > > > > What do you think of this patch? > > > > > > The Initialization flow defined in > > linux/Documentation/userspace-api/media/v4l/dev-decoder.rst > > > 1. Set the coded format on OUTPUT via VIDIOC_S_FMT(). > > > 2. Allocate source (bytestream) buffers via VIDIOC_REQBUFS() on OUTPUT. > > > 3. Start streaming on the OUTPUT queue via VIDIOC_STREAMON(). > > > 4. This step only applies to coded formats that contain resolution > > information in the stream. Continue queuing/dequeuing bytestream buffers > > to/from the OUTPUT queue via VIDIOC_QBUF() and VIDIOC_DQBUF(). The > > buffers will be processed and returned to the client in order, until > > required > > metadata to configure the CAPTURE queue are found. This is indicated by the > > decoder sending a V4L2_EVENT_SOURCE_CHANGE event with changes set to > > V4L2_EVENT_SRC_CH_RESOLUTION. > > > Note: A client capable of acquiring stream parameters from the > > bytestream on its own may attempt to set the width and height of the > > OUTPUT format to non-zero values matching the coded size of the stream, skip > > this step and continue with the Capture Setup sequence. > > > > > > 5. Continue with the Capture Setup sequence. > > > > > > In ffmpeg's implementation, ffmpeg will set non-zero width and height > > on output queue, so the step 4 should be skipped, and setup the capture > > queue directly. > > > So the flow should be: > > > 1. Set the coded format and valid resolution on OUTPUT via VIDIOC_S_FMT(). > > > 2. Allocate source (bytestream) buffers via VIDIOC_REQBUFS() on OUTPUT. > > > 3. Start streaming on the OUTPUT queue via VIDIOC_STREAMON(). > > > 5. Continue with the Capture Setup sequence. > > > > > > And this patch is just following the above flow. > > > > > > Ming > > > > The v4 version didn't work for me on odroid xu4 > > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fffmpeg.o > > rg%2Fpipermail%2Fffmpeg-devel%2F2022-January%2F290679.html&dat > > a=04%7C01%7Cming.qian%40nxp.com%7Cca988d592253473cbac408da0f3f4 > > 801%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637839061704 > > 093567%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2l > > uMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=I80bpE70S6JI > > 8A%2BaXQGq4JyxL0eBbtLN58p5SpqlA6s%3D&reserved=0 > > > > I haven't had time retest but don't think anything has changed. > > > > -- > > Andriy > > Hi Andriy, > I check the S5P MFC Video Codec driver, and indeed it requires the client > enqueue the output buffer which contains the sequence header. And in > vidioc_g_fmt(), driver will block and wait until the header is parsed. > And indeed my patch will not work on it. > But it seems don't meet the specification. > For S5P MFC, the step 4 can't be skipped, and the client should wait the > V4L2_EVENT_SOURCE_CHANGE event before the step 5 setting up capture queue. > The ffmpeg v4l2 decoder don't skip step 4, but also doesn't wait the > V4L2_EVENT_SOURCE_CHANGE event. > > So in current, we should make it work on more devices instead of more spec? Personally I'd prefer not to break users. Odroid xu4 is a popular board afaik. But I'm also not the maintainer of v4l2m2m. IMO it would be better the fix the problem in the driver first. > > The Initialization flow defined in > linux/Documentation/userspace-api/media/v4l/dev-decoder.rst > 1. Set the coded format on OUTPUT via VIDIOC_S_FMT(). > 2. Allocate source (bytestream) buffers via VIDIOC_REQBUFS() on OUTPUT. > 3. Start streaming on the OUTPUT queue via VIDIOC_STREAMON(). > 4. This step only applies to coded formats that contain resolution > information in the stream. Continue queuing/dequeuing bytestream buffers > to/from the OUTPUT queue via VIDIOC_QBUF() and VIDIOC_DQBUF(). The buffers > will be processed and returned to the client in order, until required > metadata to configure the CAPTURE queue are found. This is indicated by the > decoder sending a V4L2_EVENT_SOURCE_CHANGE event with changes set to > V4L2_EVENT_SRC_CH_RESOLUTION. > Note: A client capable of acquiring stream parameters from the > bytestream on its own may attempt to set the width and height of the OUTPUT > format to non-zero values matching the coded size of the stream, skip this > step and continue with the Capture Setup sequence. > 5. Continue with the Capture Setup sequence. -- Andriy _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
