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

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Message-ID: <4767b56f-420b-dc0c-0ae9-44dbf6dcd0b1@linaro.org>
Date:   Thu, 29 Nov 2018 12:31:01 +0200
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Tomasz Figa <tfiga@...omium.org>, mgottam@...eaurora.org
Cc:     Stanimir Varbanov <stanimir.varbanov@...aro.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 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.

> - 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
> 

-- 
regards,
Stan