Le jeudi 28 mai 2020 à 13:24 +0200, Hans Verkuil a écrit : > On 28/05/2020 12:48, dikshita@xxxxxxxxxxxxxx wrote: > > Hi Hans, > > > > Thanks for the review. > > > > On 2020-05-26 16:27, Hans Verkuil wrote: > > > Hi Dikshita, > > > > > > My apologies for the delay, this was (mostly) due to various vacation > > > days. > > > > > > On 08/05/2020 08:21, Dikshita Agarwal wrote: > > > > There are many commercialized video use cases which needs metadata > > > > info > > > > to be circulated between v4l2 client and v4l2 driver. > > > > > > > > METADATA has following requirements associated: > > > > •Metadata is an optional info available for a buffer. It is not > > > > mandatorily for every buffer. > > > > For ex. consider metadata ROI (Region Of Interest). ROI is specified > > > > by clients to indicate > > > > the region where enhanced quality is desired. This metadata is given > > > > as an input information > > > > to encoder output plane. Client may or may not specify the ROI for a > > > > frame during encode as > > > > an input metadata. Also if the client has not provided ROI metadata > > > > for a given frame, > > > > it would be incorrect to take the metadata from previous frame. If > > > > the data and > > > > metadata is asynchronous, it would be difficult for hardware to > > > > decide if it > > > > needs to wait for metadata buffer or not before processing the input > > > > frame for encoding. > > > > •Synchronize the buffer requirement across both the video node/session > > > > (incase metadata is being processed as a separate v4l2 video > > > > node/session). > > > > This is to avoid buffer starvation. > > > > •Associate the metadata buffer with the data buffer without adding any > > > > pipeline delay > > > > in waiting for each other. This is applicable both at the hardware > > > > side (the processing end) > > > > and client side (the receiving end). > > > > •Low latency usecases like WFD/split rendering/game streaming/IMS have > > > > sub-50ms e2e latency > > > > requirements, and it is not practical to stall the pipeline due to > > > > inherent framework latencies. > > > > High performance usecase like high-frame rate playback/record can > > > > lead to frame loss during any pipeline latency. > > > > > > > > To address all above requirements, we used v4l2 Request API as > > > > interlace. > > > > > > > > As an experiment, We have introduced new control > > > > V4L2_CID_MPEG_VIDEO_VENUS_METADATA > > > > to contain the METADATA info. Exact controls can be finalized once the > > > > interface is discussed. > > > > > > > > For setting metadata from userspace to kernel, let say on encode > > > > output plane, > > > > following code sequence was followed > > > > 1. Video driver is registering for media device and creating a media > > > > node in /dev > > > > 2. Request fd is allocated by calling MEDIA_IOC_REQUEST_ALLOC IOCTL on > > > > media fd. > > > > 3. METADATA configuration is being applied on request fd using > > > > VIDIOC_S_EXT_CTRLS IOCTL > > > > and the same request fd is added to buf structure structure before > > > > calling VIDIOC_QBUF on video fd. > > > > 4. The same request is queued through MEDIA_REQUEST_IOC_QUEUE IOCTL to > > > > driver then, as a result > > > > to which METADATA control will be applied to buffer through S_CTRL. > > > > 5. Once control is applied and request is completed, > > > > MEDIA_REQUEST_IOC_REINIT IOCTL is called > > > > to re-initialize the request. > > > > > > This is fine and should work well. It's what the Request API is for, > > > so no problems here. > > > > > > > We could achieve the same on capture plane as well by removing few > > > > checks present currently > > > > in v4l2 core which restrict the implementation to only output plane. > > > > > > Why do you need the Request API for the capture side in a > > > memory-to-memory driver? It is not > > > clear from this patch series what the use-case is. There are reasons > > > why this is currently > > > not allowed. So I need to know more about this. > > > > > > Regards, > > > > > > Hans > > > > > we need this for use cases like HDR10+ where metadata info is part of > > the bitstream. > > To handle such frame specific data, support for request api on capture > > plane would be needed. > > That's for the decoder, right? So the decoder extracts the HDR10+ metadata > and fills in a control with the metadata? > > If that's the case, then it matches a similar request I got from mediatek. > What is needed is support for 'read-only' requests: i.e. the driver can > associate controls with a capture buffer and return that to userspace. But > it is not possible to *set* controls in userspace when queuing the request. > > If you think about it you'll see that setting controls in userspace for > a capture queue request makes no sense, but having the driver add set > read-only controls when the request is finished is fine and makes sense. Hi Hans, I'm not sure I follow you on what will this look like in userspace. Can you post an RFC of your idea, describing the userspace flow ? Particularly, I'm not sure how the request helps in synchronizing the read of the metadata controls (over simply reading the control after a DQBUF, which we can match to a specific input using the provided timestamp). I also fail to understand how this aligns with Stanimir concern with the performance of the get control interface. > > Implementing this shouldn't be a big job: you'd need a new > V4L2_BUF_CAP_SUPPORTS_RO_REQUESTS > capability, a corresponding new flag in struct vb2_queue, a new ro_requests > flag in > struct v4l2_ctrl_handler, and try_set_ext_ctrls() should check that flag and > refuse to > try/set any controls if it is true. > > Finally, the v4l2_m2m_qbuf() function should be updated to just refuse the > case where both > capture and output queue set V4L2_BUF_CAP_SUPPORTS_REQUESTS. > > And the documentation needs to be updated. > > I've added Yunfei Dong to the CC list, perhaps mediatek did some work on > this already. > > Regards, > > Hans > > > Thanks, > > Dikshita > > > > We profiled below data with this implementation : > > > > 1. Total time taken ( round trip ) for setting up control data on > > > > video driver > > > > with VIDIOC_S_EXT_CTRLS, QBUF and Queue Request: 737us > > > > 2. Time taken for first QBUF on Output plane to reach driver with > > > > REQUEST API enabled (One way): 723us > > > > 3. Time taken for first QBUF on Output plane to reach driver without > > > > REQUEST API (One way) : 250us > > > > 4. Time taken by each IOCTL to complete ( round trip ) with REQUEST > > > > API enabled : > > > > a. VIDIOC_S_EXT_CTRLS : 201us > > > > b. VIDIOC_QBUF : 92us > > > > c. MEDIA_REQUEST_IOC_QUEUE: 386us > > > > > > > > Kindly share your feedback/comments on the design/call sequence. > > > > Also as we experimented and enabled the metadata on capture plane as > > > > well, please comment if any issue in > > > > allowing the metadata exchange on capture plane as well. > > > > > > > > Reference for client side implementation can be found at [1]. > > > > > > > > Thanks, > > > > Dikshita > > > > > > > > [1] > > > > https://git.linaro.org/people/stanimir.varbanov/v4l2-encode.git/log/?h=dikshita/request-api > > > > > > > > Dikshita Agarwal (3): > > > > Register for media device > > > > - Initialize and register for media device > > > > - define venus_m2m_media_ops > > > > - Implement APIs to register/unregister media controller. > > > > Enable Request API for output buffers > > > > - Add dependency on MEDIA_CONTROLLER_REQUEST_API in Kconfig. > > > > - Initialize vb2 ops buf_out_validate and buf_request_complete. > > > > - Add support for custom Metadata control > > > > V4L2_CID_MPEG_VIDEO_VENUS_METADATA > > > > - Implemeted/Integrated APIs for Request setup/complete. > > > > Enable Request API for Capture Buffers > > > > > > > > drivers/media/common/videobuf2/videobuf2-v4l2.c | 4 +- > > > > drivers/media/platform/Kconfig | 2 +- > > > > drivers/media/platform/qcom/venus/core.h | 36 ++++ > > > > drivers/media/platform/qcom/venus/helpers.c | 247 > > > > +++++++++++++++++++++++- > > > > drivers/media/platform/qcom/venus/helpers.h | 15 ++ > > > > drivers/media/platform/qcom/venus/venc.c | 63 +++++- > > > > drivers/media/platform/qcom/venus/venc_ctrls.c | 61 +++++- > > > > drivers/media/v4l2-core/v4l2-ctrls.c | 10 + > > > > drivers/media/v4l2-core/v4l2-mem2mem.c | 17 +- > > > > include/media/v4l2-ctrls.h | 1 + > > > > include/media/venus-ctrls.h | 22 +++ > > > > 11 files changed, 465 insertions(+), 13 deletions(-) > > > > create mode 100644 include/media/venus-ctrls.h > > > >
