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)? > > 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. >> > -- regards, Stan
