linux-kernel - Re: [PATCH v2 3/8] media: vidc: decoder: add video decoder files

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Date:   Thu, 3 Nov 2016 14:49:21 +0200
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 3/8] media: vidc: decoder: add video decoder files

Hi,

On 11/03/2016 12:55 PM, Hans Verkuil wrote:
> On 03/11/16 11:45, Stanimir Varbanov wrote:
>> Hi Hans,
>>
>> On 09/19/2016 01:04 PM, Hans Verkuil wrote:
>>> On 09/07/2016 01:37 PM, Stanimir Varbanov wrote:
>>>> This consists of video decoder implementation plus decoder
>>>> controls.
>>>>
>>>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>>>> ---
>>>>  drivers/media/platform/qcom/vidc/vdec.c       | 1091
>>>> +++++++++++++++++++++++++
>>>>  drivers/media/platform/qcom/vidc/vdec.h       |   29 +
>>>>  drivers/media/platform/qcom/vidc/vdec_ctrls.c |  200 +++++
>>>>  drivers/media/platform/qcom/vidc/vdec_ctrls.h |   21 +
>>>>  4 files changed, 1341 insertions(+)
>>>>  create mode 100644 drivers/media/platform/qcom/vidc/vdec.c
>>>>  create mode 100644 drivers/media/platform/qcom/vidc/vdec.h
>>>>  create mode 100644 drivers/media/platform/qcom/vidc/vdec_ctrls.c
>>>>  create mode 100644 drivers/media/platform/qcom/vidc/vdec_ctrls.h
>>>>
>>
>> <cut>
>>
>>>> +
>>>> +static int
>>>> +vdec_g_selection(struct file *file, void *priv, struct
>>>> v4l2_selection *s)
>>>> +{
>>>> +    struct vidc_inst *inst = to_inst(file);
>>>> +
>>>> +    if (s->type != V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
>>>> +        return -EINVAL;
>>>> +
>>>> +    switch (s->target) {
>>>> +    case V4L2_SEL_TGT_CROP_DEFAULT:
>>>> +    case V4L2_SEL_TGT_CROP_BOUNDS:
>>>> +    case V4L2_SEL_TGT_CROP:
>>>> +    case V4L2_SEL_TGT_COMPOSE_DEFAULT:
>>>> +    case V4L2_SEL_TGT_COMPOSE_BOUNDS:
>>>> +    case V4L2_SEL_TGT_COMPOSE:
>>>
>>> This is almost certainly wrong.
>>>
>>> For capture I would expect that you can do compose, but not crop.
>>>
>>> This would likely explain that v4l2-compliance thinks that the driver
>>> can
>>> scale:
>>>
>>>                 test Scaling: OK
>>>
>>
>> Maybe I need some help to implement correctly g_selection.
>>
>> Lets say that the resolution of the compressed stream is 1280x720, and
>> that resolution is set with s_fmt(OUTPUT queue), then I calculate the
>> output resolution which I will return by g_fmt(CAPTURE queue) and it
>> will be 1280x736 (hardware wants height to be multiple of 32 lines). So
>> the result will be 16 lines of vertical padding which should be exposed
>> to client (think of gstreamer v4l2videodec element) via g_crop
>> (g_selection) as 1280x720 because this is the actual image.
>>
>> So from what I understood while read Selection API, I need to support
>> only composing on CAPTURE queue, no scaling and no cropping.
>>
>> OUTPUT buffer type, data source
>> TGT_CROP_BOUNDS = TGT_CROP_DEFAULT = TGT_CROP = 1280x720
>> TGT_COMPOSE_BOUNDS = TGT_COMPOSE_DEFAULT = TGT_COMPOSE = 1280x720
> 
> The output buffer type doesn't do composition, only crop. So you shouldn't
> support the compose targets.

OK I tried to return EINVAL for compose targets for output buffer type
and the result is :

	test Cropping: OK
	test Composing: OK
	test Scaling: OK

Which is odd because now Scaling is supported.

> 
>>
>> CAPTURE buffer type, data sink
>> TGT_CROP_BOUNDS = TGT_CROP_DEFAULT = TGT_CROP = EINVAL
>> TGT_COMPOSE_BOUNDS = 1280x736
>> TGT_COMPOSE_DEFAULT = TGT_COMPOSE = 1280x720
> 
> This looks good.
> 
>>
>> With this logic in g_selection the output of v4l2-compliance test
>> application is:
>>     test Cropping: OK
>>     test Composing: OK
>>     test Scaling: OK (Not Supported)
>>
>> So why v4l2-compliance still thinks that the driver supports Cropping?
> 
> Hmm, v4l2-compliance could be improved. The problem is that it doesn't
> show for m2m devices for which side (capture or output) cropping, composing
> or scaling is supported. It does test both sides, but you can't tell from
> the output.
> 
> It's a bit confusing in this case.

OK I will incorporate the above g_selection behavior and send a new
version of the patches, I do not waste time on that. The drawback is
that this padding will be displayed as green bar on bottom of the
displayed image, although the gstreamer master branch now use
g_selection so probably it should be fine there.

> 
> Regards,
> 
>     Hans
> 
>>
>>>> +        break;
>>>> +    default:
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    s->r.top = 0;
>>>> +    s->r.left = 0;
>>>> +    s->r.width = inst->out_width;
>>>> +    s->r.height = inst->out_height;
>>>> +
>>>> +    return 0;
>>>> +}
>>
>> <cut>
>>

-- 
regards,
Stan