Hi Dmitry, On Fri, Dec 20, 2019 at 11:25 PM Dmitry Sepp <dmitry.sepp@xxxxxxxxxxxxxxx> wrote: > > Hi Keiichi, > > Could you please explain in a more detailed way what exactly CROP is used for? > Is it equivalent to G/S_CROP or G/S_SELECTION in v4l2? Do you only need to get > it, or to set as well? Can it also be useful for the encoder? It corresponds to struct v4l2_rect in V4L2, which is used in G/S_SELECTION. IIUC, G/S_SELECTION is a kind of super set of G/S_CROP. Both decoder and encoder can utilize both G_SELECTION and S_SELECTION. Their usages are documented in the specs of V4L2 stateful decoder/encoder API. stateful decoder spec: https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/dev-decoder.html stateful encoder spec (in maintainer's tree): https://hverkuil.home.xs4all.nl/codec-api/uapi/v4l/dev-encoder.html Best regards, Keiichi > > Regrds, > Dmitry. > > On Freitag, 13. Dezember 2019 17:31:24 CET Keiichi Watanabe wrote: > > On Fri, Dec 13, 2019 at 11:20 PM Keiichi Watanabe <keiichiw@xxxxxxxxxxxx> > wrote: > > > On Thu, Dec 12, 2019 at 7:34 PM Dmitry Sepp <dmitry.sepp@xxxxxxxxxxxxxxx> > wrote: > > > > Hi Keiichi, > > > > > > > > Thank you for your comment. > > > > What do you thing about selection/crop rectangles? Should this be > > > > defined as a must have? Or we just assume the device always sticks to > > > > the stream resolution. > > > > > > For decoding, the device needs to tell the driver crop rectangle when > > > a resolution change happens, as virtio-vdec has > > > virtio_vdec_host_req_stream_crop. > > > So, we should add a new field in virtio_video_param for it. > > > > > > For what it's worth, we have C-headers that exposes Chrome's video > > > codec functionalities. So, our virtio-video device will do > > > decoding/encoding by calling these functions. > > > Decoder: > > > https://chromium.git.corp.google.com/chromiumos/platform2/+/00ad71fa640c0 > > > 18c1d014f467c50b9a7dc962a10/arc/vm/libvda/libvda_decode.h Encoder: > > > https://chromium.git.corp.google.com/chromiumos/platform2/+/00ad71fa640c0 > > > 18c1d014f467c50b9a7dc962a10/arc/vm/libvda/libvda_encode.h > > Oops, the links were not accesible... > > The correct links are: > > Decoder: > > https://chromium.googlesource.com/chromiumos/platform2/+/00ad71fa640c018c1d > > 014f467c50b9a7dc962a10/arc/vm/libvda/libvda_decode.h Encoder: > > https://chromium.googlesource.com/chromiumos/platform2/+/00ad71fa640c018c1d > > 014f467c50b9a7dc962a10/arc/vm/libvda/libvda_encode.h > > > > Best, > > Keiichi > > > > > BTW, I'm preparing the next version of virtio-video spec by addressing > > > points we discussed in this thread. I'll send it here next week, > > > hopefully. > > > > > > Best, > > > Keiichi > > > > > > > Regards, > > > > Dmitry. > > > > > > > > On Donnerstag, 12. Dezember 2019 06:39:11 CET Keiichi Watanabe wrote: > > > > > On Tue, Dec 10, 2019 at 10:16 PM Dmitry Sepp > > > > > > > > > > <dmitry.sepp@xxxxxxxxxxxxxxx> wrote: > > > > > > Hi, > > > > > > > > > > > > Just to start, let's consider this v4l2 control: > > > > > > V4L2_CID_MPEG_VIDEO_FRAME_RC_ENABLE. > > > > > > As I can see, this control is referenced as a mandatory one in the > > > > > > Chromium > > > > > > sources [1]. > > > > > > > > > > > > So could someone from the Chromium team please explain why it is > > > > > > mandatory? > > > > > > (YouTube?) In fact, almost no encoders implement this control. Do we > > > > > > need > > > > > > it in virtio-video? > > > > > > > > > > That control is used to encode videos in constant bitrate (CBR) mode, > > > > > which is critical for > > > > > real-time use case like video conferencing. > > > > > > > > > > However, that Chromium source code just requires *host-side* drivers > > > > > to have the v4l2 > > > > > control. Also, I guess it's rare that a guest app wants to use CQP > > > > > instead of CBR from our > > > > > experience. > > > > > So, I suppose we can omit this control in virtio spec for now by > > > > > assuming that guests > > > > > always use CBR mode. > > > > > > > > > > Best regards, > > > > > Keiichi > > > > > > > > > > > [1] > > > > > > https://chromium.googlesource.com/chromium/src/media/+/refs/heads/ma > > > > > > ster/ > > > > > > gpu/v4l2/v4l2_video_encode_accelerator.cc#1500 > > > > > > > > > > > > Regards, > > > > > > Dmitry. > > > > > > > > > > > > On Montag, 9. Dezember 2019 22:12:28 CET Enrico Granata wrote: > > > > > > > +Changyeon Jo <changyeon@xxxxxxxxxx> for his awareness > > > > > > > > > > > > > > Thanks, > > > > > > > - Enrico > > > > > > > > > > > > > > > > > > > > > On Mon, Dec 9, 2019 at 6:20 AM Dmitry Sepp > > > > > > > <dmitry.sepp@xxxxxxxxxxxxxxx> > > > > > > > > > > > > > > wrote: > > > > > > > > Hello, > > > > > > > > > > > > > > > > I'd like to invite everyone to share ideas regarding required > > > > > > > > encoder > > > > > > > > features > > > > > > > > in this separate sub-tree. > > > > > > > > > > > > > > > > In general, encoder devices are more complex compared to > > > > > > > > decoders. So > > > > > > > > the > > > > > > > > question I'd like to rise is in what way we define the minimal > > > > > > > > subset > > > > > > > > of > > > > > > > > features to be implemented by the virtio-video. > > > > > > > > > > > > > > > > We may look at the following to define the set of features: > > > > > > > > 1. USB video, 2.3.6 Encoding Unit [1]. > > > > > > > > 2. Android 10 Compatibility Definition [2]. > > > > > > > > > > > > > > > > Would be nice to hear about any specific requirements from the > > > > > > > > Chromium > > > > > > > > team as > > > > > > > > well. > > > > > > > > > > > > > > > > [1] > > > > > > > > https://www.usb.org/sites/default/files/USB_Video_Class_1_5.zip > > > > > > > > [2] > > > > > > > > https://source.android.com/compatibility/android-cdd#5_2_video_e > > > > > > > > ncodin > > > > > > > > g > > > > > > > > > > > > > > > > Thank you. > > > > > > > > > > > > > > > > Best regards, > > > > > > > > Dmitry. > > > > > > > > > > > > > > > > On Mittwoch, 4. Dezember 2019 10:16:20 CET Gerd Hoffmann wrote: > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > 1. Focus on only decoder/encoder functionalities first. > > > > > > > > > > > > > > > > > > > > As Tomasz said earlier in this thread, it'd be too > > > > > > > > > > complicated to > > > > > > > > > > > > > > > > support > > > > > > > > > > > > > > > > > > camera usage at the same time. So, I'd suggest to make it > > > > > > > > > > just a > > > > > > > > > > > > > > > > generic > > > > > > > > > > > > > > > > > > mem-to-mem video processing device protocol for now. > > > > > > > > > > If we finally decide to support camera in this protocol, we > > > > > > > > > > can > > > > > > > > > > add it > > > > > > > > > > later. > > > > > > > > > > > > > > > > > > Agree. > > > > > > > > > > > > > > > > > > > 2. Only one feature bit can be specified for one device. > > > > > > > > > > > > > > > > > > > > I'd like to have a decoder device and encoder device > > > > > > > > > > separately. > > > > > > > > > > It'd be natural to assume it because a decoder and an > > > > > > > > > > encoder are > > > > > > > > > > > > > > > > provided > > > > > > > > > > > > > > > > > > as different hardware. > > > > > > > > > > > > > > > > > > Hmm, modern GPUs support both encoding and decoding ... > > > > > > > > > > > > > > > > > > I don't think we should bake that restriction into the > > > > > > > > > specification. > > > > > > > > > It probably makes sense to use one virtqueue per function > > > > > > > > > though, > > > > > > > > > that > > > > > > > > > will simplify dispatching in both host and guest. > > > > > > > > > > > > > > > > > > > 3. Separate buffer allocation functionalities from > > > > > > > > > > virtio-video > > > > > > > > > > > > > > > > protocol. > > > > > > > > > > > > > > > > > > To support various ways of guest/host buffer sharing, we > > > > > > > > > > might > > > > > > > > > > want to > > > > > > > > > > have a dedicated buffer sharing device as we're discussing > > > > > > > > > > in > > > > > > > > > > another > > > > > > > > > > thread. Until we reach consensus there, it'd be good not to > > > > > > > > > > have > > > > > > > > > > buffer > > > > > > > > > > allocation > > > > > > > > > > functionalities in virtio-video. > > > > > > > > > > > > > > > > > > I think virtio-video should be able to work as stand-alone > > > > > > > > > device, > > > > > > > > > so we need some way to allocate buffers ... > > > > > > > > > > > > > > > > > > Buffer sharing with other devices can be added later. > > > > > > > > > > > > > > > > > > > > +The virtio video device is a virtual video streaming > > > > > > > > > > > device > > > > > > > > > > > that > > > > > > > > > > > supports the +following functions: encoder, decoder, > > > > > > > > > > > capture, > > > > > > > > > > > output. > > > > > > > > > > > + > > > > > > > > > > > +\subsection{Device ID}\label{sec:Device Types / Video > > > > > > > > > > > Device / > > > > > > > > > > > > > > > > Device > > > > > > > > > > > > > > > > > > > ID} > > > > > > > > > > > + > > > > > > > > > > > +TBD. > > > > > > > > > > > > > > > > > > > > I'm wondering how and when we can determine and reserve this > > > > > > > > > > ID? > > > > > > > > > > > > > > > > > > Grab the next free, update the spec accordingly, submit the > > > > > > > > > one-line > > > > > > > > > patch. > > > > > > > > > > > > > > > > > > > > +\begin{lstlisting} > > > > > > > > > > > +enum virtio_video_pixel_format { > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_UNDEFINED = 0, > > > > > > > > > > > + > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_H264 = 0x0100, > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_NV12, > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_NV21, > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_I420, > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_I422, > > > > > > > > > > > + VIRTIO_VIDEO_PIX_FMT_XBGR, > > > > > > > > > > > +}; > > > > > > > > > > > > > > > > > > > > I'm wondering if we can use FOURCC instead. So, we can avoid > > > > > > > > > > > > > > > > reinventing a > > > > > > > > > > > > > > > > > > mapping from formats to integers. > > > > > > > > > > Also, I suppose the word "pixel formats" means only raw > > > > > > > > > > (decoded) > > > > > > > > > > > > > > > > formats. > > > > > > > > > > > > > > > > > > But, it can be encoded format like H.264. So, I guess "image > > > > > > > > > > format" > > > > > > > > > > or > > > > > > > > > > "fourcc" is a better word choice. > > > > > > > > > > > > > > > > > > Use separate pixel_format (fourcc) and stream_format (H.264 > > > > > > > > > etc.) > > > > > > > > > enums? > > > > > > > > > > > > > > > > > > > > +\begin{lstlisting} > > > > > > > > > > > +struct virtio_video_function { > > > > > > > > > > > + struct virtio_video_desc desc; > > > > > > > > > > > + __le32 function_type; /* One of > > > > > > > > > > > VIRTIO_VIDEO_FUNC_* > > > > > > > > > > > types */ > > > > > > > > > > > + __le32 function_id; > > > > > > > > > > > + struct virtio_video_params in_params; > > > > > > > > > > > + struct virtio_video_params out_params; > > > > > > > > > > > + __le32 num_caps; > > > > > > > > > > > + __u8 padding[4]; > > > > > > > > > > > + /* Followed by struct virtio_video_capability > > > > > > > > > > > video_caps[]; > > > > > > > > > > > > > > > > */ > > > > > > > > > > > > > > > > > > > +}; > > > > > > > > > > > +\end{lstlisting} > > > > > > > > > > > > > > > > > > > > If one device only has one functionality, > > > > > > > > > > virtio_video_function's > > > > > > > > > > > > > > > > fields > > > > > > > > > > > > > > > > > > will be no longer needed except in_params and out_params. > > > > > > > > > > So, we'd > > > > > > > > > > be > > > > > > > > > > able to remove virtio_video_function and have in_params and > > > > > > > > > > out_params > > > > > > > > > > > > > > > > in > > > > > > > > > > > > > > > > > > virtio_video_capability instead. > > > > > > > > > > > > > > > > > > Same goes for per-function virtqueues (used virtqueue implies > > > > > > > > > function). > > > > > > > > > > > > > > > > > > > > +\begin{lstlisting} > > > > > > > > > > > +struct virtio_video_resource_detach_backing { > > > > > > > > > > > + struct virtio_video_ctrl_hdr hdr; > > > > > > > > > > > + __le32 resource_id; > > > > > > > > > > > + __u8 padding[4]; > > > > > > > > > > > +}; > > > > > > > > > > > +\end{lstlisting} > > > > > > > > > > > + > > > > > > > > > > > +\begin{description} > > > > > > > > > > > +\item[\field{resource_id}] internal id of the resource. > > > > > > > > > > > +\end{description} > > > > > > > > > > > > > > > > > > > > I suppose that it'd be better not to have the above series > > > > > > > > > > of > > > > > > > > > > > > > > > > T_RESOURCE > > > > > > > > > > > > > > > > > > controls at least until we reach a conclusion in the thread > > > > > > > > > > of > > > > > > > > > > buffer-sharing device. If we end up concluding this type of > > > > > > > > > > controls > > > > > > > > > > is > > > > > > > > > > the best way, we'll be able to revisit here. > > > > > > > > > > > > > > > > > > Well. For buffer management there are a bunch of options. > > > > > > > > > > > > > > > > > > (1) Simply stick the buffers (well, pointers to the buffer > > > > > > > > > pages) > > > > > > > > > into > > > > > > > > > > > > > > > > > > the virtqueue. This is the standard virtio way. > > > > > > > > > > > > > > > > > > (2) Create resources, then put the resource ids into the > > > > > > > > > virtqueue. > > > > > > > > > > > > > > > > > > virtio-gpu uses that model. First, because virtio-gpu > > > > > > > > > needs an > > > > > > > > > id > > > > > > > > > to reference resources in the rendering command stream > > > > > > > > > (virtio-video doesn't need this). Also because (some > > > > > > > > > kinds of) > > > > > > > > > resources are around for a long time and the > > > > > > > > > guest-physical -> > > > > > > > > > host-virtual mapping needs to be done only once that way > > > > > > > > > (which > > > > > > > > > I think would be the case for virtio-video too because > > > > > > > > > v4l2 > > > > > > > > > re-uses buffers in robin-round fashion). Drawback is > > > > > > > > > this > > > > > > > > > assumes shared memory between host and guest (which is > > > > > > > > > the case > > > > > > > > > in typical use cases but it is not mandated by the virtio > > > > > > > > > spec). > > > > > > > > > > > > > > > > > > (3) Import external resources (from virtio-gpu for example). > > > > > > > > > > > > > > > > > > Out of scope for now, will probably added as optional > > > > > > > > > feature > > > > > > > > > later. > > > > > > > > > > > > > > > > > > I guess long-term we want support either (1)+(3) or (2)+(3). > > > > > > > > > > > > > > > > > > cheers, > > > > > > > > > > > > > > > > > > Gerd > > > > > > > > > > > > > > > > ---------------------------------------------------------------- > > > > > > > > ----- > > > > > > > > To unsubscribe, e-mail: > > > > > > > > virtio-dev-unsubscribe@xxxxxxxxxxxxxxxxxxxx > > > > > > > > For additional commands, e-mail: > > > > > > > > virtio-dev-help@xxxxxxxxxxxxxxxxxxxx > >
