On Tue, Oct 13, 2020 at 2:52 PM Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx> wrote: > > 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. How comes it can be decoded without additional memory to store the reference frames then? > Also no matter frame parser is sending, the decoder will > try to produce output for thumbnail generation. Well, thinking of it now, actually DECODE_INTRA_FRAMES_ONLY makes sense here - if it is set, only 1 CAPTURE buffer could be allowed indeed, because no reference frames are needed for decoding. If inter frames are needed, I believe full DPB needs to be allocated, because it all depends on the stream how the references are set, so this is equivalent to normal decoding. best regards, Tomasz > > > 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
