Hi, On 6/4/20 3:57 PM, Tomasz Figa wrote: > 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." > In fact I have to refine this; It looks like that picture type decode vs thumbnail are two different modes. Thumbnail mode - first frame decode without additional memory (one input buffer and one output buffer). The first frame can be even non-intra frame as well. Also no matter frame parser is sending, the decoder will try to produce output for thumbnail generation. > 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. >>>>> >>>> >>> >> -- regards, Stan
