On Mon, May 27, 2019 at 4:39 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > On 5/27/19 5:51 AM, Tomasz Figa wrote: > > On Tue, May 21, 2019 at 9:27 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > >> > >> On 5/21/19 11:09 AM, Tomasz Figa wrote: > >>> Hi Stan, > >>> > >>> On Mon, May 20, 2019 at 11:47 PM Stanimir Varbanov > >>> <stanimir.varbanov@xxxxxxxxxx> wrote: > >>>> > >>>> Hi Tomasz, > >>>> > >>>> On 4/24/19 3:39 PM, Tomasz Figa wrote: > >>>>> On Wed, Apr 24, 2019 at 9:15 PM Stanimir Varbanov > >>>>> <stanimir.varbanov@xxxxxxxxxx> wrote: > >>>>>> > >>>>>> Hi Hans, > >>>>>> > >>>>>> On 2/15/19 3:44 PM, Hans Verkuil wrote: > >>>>>>> Hi Stanimir, > >>>>>>> > >>>>>>> I never paid much attention to this patch series since others were busy > >>>>>>> discussing it and I had a lot of other things on my plate, but then I heard > >>>>>>> that this patch made G_FMT blocking. > >>>>>> > >>>>>> OK, another option could be to block REQBUF(CAPTURE) until event from hw > >>>>>> is received that the stream is parsed and the resolution is correctly > >>>>>> set by application. Just to note that I'd think to this like a temporal > >>>>>> solution until gstreamer implements v4l events. > >>>>>> > >>>>>> Is that looks good to you? > >>>>> > >>>>> Hmm, I thought we concluded that gstreamer sets the width and height > >>>>> in OUTPUT queue before querying the CAPTURE queue and so making the > >>>>> driver calculate the CAPTURE format based on what's set on OUTPUT > >>>>> would work fine. Did I miss something? > >>>> > >>>> Nobody is miss something. > >>>> > >>>> First some background about how Venus implements stateful codec API. > >>>> > >>>> The Venus firmware can generate two events "sufficient" and > >>>> "insufficient" buffer requirements (this includes decoder output buffer > >>>> size and internal/scratch buffer sizes). Presently I always set minimum > >>>> possible decoder resolution no matter what the user said, and by that > >>>> way I'm sure that "insufficient" event will always be triggered by the > >>>> firmware (the other reason to take this path is because this is the > >>>> least-common-divider for all supported Venus hw/fw versions thus common > >>>> code in the driver). The reconfiguration (during codec Initialization > >>>> sequence) is made from STREAMON(CAPTURE) context. Now, to make that > >>>> re-configuration happen I need to wait for "insufficient" event from > >>>> firmware in order to know the real coded resolution. > >>>> > >>>> In the case of gstreamer where v4l2_events support is missing I have to > >>>> block (wait for firmware event) REQBUF(CAPTURE) (vb2::queue_setup) or > >>>> STREAMON(CAPTURE) (vb2::start_streaming). > >>>> > >>>> I tried to set the coded resolution to the firmware as-is it set by > >>>> gstreamer but then I cannot receive the "sufficient" event for VP8 and > >>>> VP9 codecs. So I return back to the solution with minimum resolution above. > >>>> > >>>> I'm open for suggestions. > >>> > >>> I think you could still keep setting the minimum size and wait for the > >>> "insufficient" event. At the same time, you could speculatively > >>> advertise the expected "sufficient" size on the CAPTURE queue before > >>> the hardware signals those. Even if you mispredict them, you'll get > >>> the event, update the CAPTURE resolution and send the source change > >>> event to the application, which would then give you the correct > >>> buffers. Would that work for you? > >> > >> As I understand it this still would require event support, which gstreamer > >> doesn't have. > > > > I don't think it matches what I remember from the earlier discussion. > > As long as Gstreamer sets the visible resolution (from the container > > AFAIR) on OUTPUT, the driver would adjust it to something that is > > expected to be the right framebuffer resolution and so Gstreamer would > > be able to continue. Of course if the expected value doesn't match, it > > wouldn't work, but it's the same as currently for Coda AFAICT. > > > >> > >> I think it is OK to have REQBUFS sleep in this case. However, I would only > > > > Why REQBUFS? While that could possibly allow us to allocate the right > > buffers, Gstreamer wouldn't be able to know the right format, because > > it would query it before REQBUFS, wouldn't it? > > Oops, you are right. It's got to be in G_FMT(CAPTURE), but *only* if > nobody subscribed to the SOURCE_CHANGE event. > > > > > For this reason, s5p-mfc makes G_FMT(CAPTURE) blocking and if we > > decide to forcefully keep the compatibility, even with in drivers, we > > should probably do the same here. > > > >> enable this behavior if the application didn't subscribe to the SOURCE_CHANGE > >> event. That's easy enough to check in the driver. And that means that if the > >> application is well written, then the driver will behave in a completely > >> standard way that the compliance test can check. > > > > I guess one could have some helpers for this. They would listen to the > > source change events internally and block / wake-up appropriate ioctls > > whenever necessary. > > I really do not want this for new drivers. gstreamer should be fixed. > A blocking G_FMT is just plain bad. Only those drivers that do this, can > still block if nobody subscribed to EVENT_SOURCE_CHANGE. Yeah and that's why I just suggested to mimic coda, which doesn't block, but apparently gstreamer still works with it. > > > Another question: If we intend this to be implemented in new drivers > > too, should it be documented in the spec? > > We most certainly do NOT want to implement this in new drivers. > Makes sense. When venus was merged initially, did it already have a blocking G_FMT? Best regards, Tomasz
