linux-kernel - Re: [PATCH v3] media: venus: add support for key frame

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Date:   Thu, 29 Nov 2018 16:40:36 +0530
From:   mgottam@...eaurora.org
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        vgarodia@...eaurora.org
Subject: Re: [PATCH v3] media: venus: add support for key frame


Hi Stan,

On 2018-11-29 16:01, Stanimir Varbanov wrote:
> Hi Tomasz,
> 
> On 11/3/18 5:01 AM, Tomasz Figa wrote:
>> Hi Malathi,
>> 
>> On Fri, Nov 2, 2018 at 9:58 PM Malathi Gottam <mgottam@...eaurora.org> 
>> wrote:
>>> 
>>> When client requests for a keyframe, set the property
>>> to hardware to generate the sync frame.
>>> 
>>> Signed-off-by: Malathi Gottam <mgottam@...eaurora.org>
>>> ---
>>>  drivers/media/platform/qcom/venus/venc_ctrls.c | 20 
>>> +++++++++++++++++++-
>>>  1 file changed, 19 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/drivers/media/platform/qcom/venus/venc_ctrls.c 
>>> b/drivers/media/platform/qcom/venus/venc_ctrls.c
>>> index 45910172..59fe7fc 100644
>>> --- a/drivers/media/platform/qcom/venus/venc_ctrls.c
>>> +++ b/drivers/media/platform/qcom/venus/venc_ctrls.c
>>> @@ -79,8 +79,10 @@ static int venc_op_s_ctrl(struct v4l2_ctrl *ctrl)
>>>  {
>>>         struct venus_inst *inst = ctrl_to_inst(ctrl);
>>>         struct venc_controls *ctr = &inst->controls.enc;
>>> +       struct hfi_enable en = { .enable = 1 };
>>>         u32 bframes;
>>>         int ret;
>>> +       u32 ptype;
>>> 
>>>         switch (ctrl->id) {
>>>         case V4L2_CID_MPEG_VIDEO_BITRATE_MODE:
>>> @@ -173,6 +175,19 @@ static int venc_op_s_ctrl(struct v4l2_ctrl 
>>> *ctrl)
>>> 
>>>                 ctr->num_b_frames = bframes;
>>>                 break;
>>> +       case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
>>> +               mutex_lock(&inst->lock);
>>> +               if (inst->streamon_out && inst->streamon_cap) {
>> 
>> We had a discussion on this in v2. I don't remember seeing any 
>> conclusion.
>> 
>> Obviously the hardware should generate a keyframe naturally when the
>> CAPTURE streaming starts, which is where the encoding starts, but the
>> state of the OUTPUT queue should not affect this.
>> 
>> The application is free to stop and start streaming on the OUTPUT
>> queue as it goes and it shouldn't imply any side effects in the
>> encoded bitstream (e.g. a keyframe inserted). So:
>> - a sequence of STREAMOFF(OUTPUT),
>> S_CTRL(V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME), STREAMON(OUTPUT) should
>> explicitly generate a keyframe,
> 
> I agree with you, but presently we don't follow strictly the stateful
> encoder spec. In this spirit I think proposed patch is applicable to 
> the
> current state of the encoder driver, and your comment should be
> addressed in the follow-up patches where we have to re-factor a bit
> start/stop_streaming according to the encoder documentation.
> 
> But until then we have to get that patch.

So I can see that this patch is good implementation of forcing sync 
frame
under current encoder state.

Can you please ack the same.

Thanks,
Malathi.

> 
>> - a sequence of STREAMOFF(OUTPUT), STREAMON(OUTPUT) should _not_
>> explicitly generate a keyframe (the hardware may generate one, if the
>> periodic keyframe counter is active or a scene detection algorithm
>> decides so).
>> 
>> Please refer to the specification (v2 is the latest for the time being
>> -> https://lore.kernel.org/patchwork/patch/1002476/) for further
>> details and feel free to leave any comment for it.
>> 
>> Best regards,
>> Tomasz
>>