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. 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. >>> >> >
