Hi, On 5/27/19 11:18 AM, Tomasz Figa wrote: > 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. Unfortunately in Venus case that is not an easy task (as I tried to explain why above). To have an unified and common code for all different SoCs and firmware/hardware versions I decided to set the minimum supported resolution for the decoder (no matter what the user said) and trigger the reconfiguration event always. Something more, I need the event also to retrieve the minimum capture buffers (V4L2_CID_MIN_BUFFERS_FOR_CAPTURE) and sizes for capture and internal/scratch buffers as well, thus I really need to wait for that event. So, just to confirm - you are fine with blocking G_FMT (not REQBUF) when the user doesn't subscribe for v4l2 events? > >> >>> 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? No it isn't. -- regards, Stan
