On Thu, Jun 4, 2020 at 2:56 PM Hans Verkuil <hverkuil-cisco@xxxxxxxxx> wrote: > > On 04/06/2020 14:34, Stanimir Varbanov wrote: > > Hi Hans, > > > > On 6/4/20 12:08 PM, Hans Verkuil wrote: > >> On 04/06/2020 11:02, Stanimir Varbanov wrote: > >>> Hi Hans, > >>> > >>> On 5/27/20 12:53 AM, Stanimir Varbanov wrote: > >>>> Hi Hans, > >>>> > >>>> On 5/26/20 3:04 PM, Hans Verkuil wrote: > >>>>> On 26/05/2020 10:54, Stanimir Varbanov wrote: > >>>>>> Add v4l2 control for decoder thumbnail. > >>>>>> > >>>>>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx> > >>>>>> --- > >>>>>> Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 7 +++++++ > >>>>>> drivers/media/v4l2-core/v4l2-ctrls.c | 2 ++ > >>>>>> include/uapi/linux/v4l2-controls.h | 2 ++ > >>>>>> 3 files changed, 11 insertions(+) > >>>>>> > >>>>>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst > >>>>>> index d0d506a444b1..e838e410651b 100644 > >>>>>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst > >>>>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst > >>>>>> @@ -3726,6 +3726,13 @@ enum v4l2_mpeg_video_hevc_size_of_length_field - > >>>>>> disables generating SPS and PPS at every IDR. Setting it to one enables > >>>>>> generating SPS and PPS at every IDR. > >>>>>> > >>>>>> +``V4L2_CID_MPEG_VIDEO_DECODER_THUMBNAIL (button)`` > >>>>>> + Instructs the decoder to produce immediate output. The decoder should > >>>>>> + consume first input buffer for progressive stream (or first two buffers > >>>>>> + for interlace). Decoder should not allocate more output buffers that it > >>>>>> + is required to consume one input frame. Usually the decoder input > >>>>>> + buffers will contain only I/IDR frames but it is not mandatory. > >>>>> > >>>>> This is very vague. It doesn't explain why the control is called 'THUMBNAIL', > >>>>> but more importantly it doesn't explain how this relates to normal decoding. > >>>> > >>>> If in the normal decode the capture queue buffers are 5, in the > >>>> thumbnail mode the number of buffers will be only 1 (if the bitstream is > >>>> progressive) and this will guarantee low memory usage. The other > >>>> difference is that the decoder will produce decoded frames (without > >>>> errors) only for I/IDR (sync frames). > >> > >> Isn't this really a "DECODE_SYNC_FRAMES_ONLY" control? That's what it does, > >> right? Skip any B/P frames and only decode sync frames. > > > > Yes, it is. > > To me V4L2_CID_MPEG_VIDEO_DECODE_SYNC_FRAMES sounds better. If you are > > fine I can send a new patch. > > > > The definition of "sync frames" is a bit difficult for codec-agnostic > > controls. Is it sound better "INTRA", DECODE_INTRA_FRAMES (ONLY)? > > INTRA is better. DECODE_INTRA_FRAMES_ONLY is a good name, I think. > > Thumbnail creation can be given as an example in the description of the > control, but that's just a use-case. How about the other aspect of the behavior? "Decoder should not allocate more output buffers that it is required to consume one input frame." Best regards, Tomasz > > Regards, > > Hans > > > > >> > >> That this is useful for creating thumbnails is just a specific use-case. > >> > >> Regards, > >> > >> Hans > >> > >>>> > >>>>> > >>>>> I.e. if you are decoding and 'press' this control, what happens then? > >>>> > >>>> Might be the button type wasn't great idea. In fact the control should > >>>> be set before streamon so that the driver returns min_capture_bufs 1. > >>>> > >>>>> > >>>>> What exactly is the use-case? > >>>> > >>>> It could be used to generate thumbnails of all video clips in a folder > >>>> or when you open a Gallery application on your phone. > >>>> > >>> > >>> What is your opinion on that control? I could consider to make it Venus > >>> custom control but from the use-case it looks other drivers also can > >>> benefit of it. > >>> > >>> I tried to make more generic one [1] but it looks it will be too difficult. > >>> > >> > > >
