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

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Date:   Sat, 3 Nov 2018 12:01:01 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     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 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,
- 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