linux-kernel - Re: [PATCH v2 00/11] Venus stateful Codec API

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Date:   Fri, 28 Jun 2019 17:23:45 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Vikash Garodia <vgarodia@...eaurora.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>
Subject: Re: [PATCH v2 00/11] Venus stateful Codec API

Hi Hans,

On 6/28/19 4:37 PM, Hans Verkuil wrote:
> On 6/28/19 2:59 PM, Stanimir Varbanov wrote:
>> Hello,
>>
>> Here is v2 of the Venus transition to stateful codec API
>> compliance. The v2 can be found at [1].
>>
>> Changes since v1:
>>  * codec_state is now enum
>>  * dropped IS_OUT and IS_CAP macros and use vb2_start_streaming_called()
>>  * corrected g_fmt and reconfig logic
>>  * s/vdec_dst_buffers_done/vdec_cancel_dst_buffers
>>  * use v4l2_m2m_ioctl_try_decoder_cmd M2M helper
>>  * various fixes to make v4l2-compliance pass the streaming test
>>
>> To test the streaming with --stream-from-hdr v4l2-compliance option I have
>> to make the following hack (it is needed because the size of decoder input
>> buffers (OUTPUT queue) is not enough for the h264 bitstream, i.e the driver
>> default resolution is 64x64 but the h264 stream is 320x240):
>>
>> diff --git a/utils/v4l2-compliance/v4l2-test-buffers.cpp b/utils/v4l2-compliance/v4l2-test-buffers.cpp
>> index c71dcf65b721..dc0fcf20d3e4 100644
>> --- a/utils/v4l2-compliance/v4l2-test-buffers.cpp
>> +++ b/utils/v4l2-compliance/v4l2-test-buffers.cpp
>> @@ -1294,6 +1294,11 @@ int testMmap(struct node *node, unsigned frame_count, enum poll_mode pollmode)
>>                                         fmt.s_sizeimage(fmt.g_sizeimage(p) * 2, p);
>>                         }
>>                         fail_on_test(q.create_bufs(node, 1, &fmt));
>> +
>> +                       for (unsigned p = 0; p < fmt.g_num_planes(); p++)
>> +                               fmt.s_sizeimage(fmt.g_sizeimage(p) * 2, p);
>> +                       node->s_fmt(fmt);
>> +
>>                         fail_on_test(q.reqbufs(node, 2));
>>                 }
>>                 if (v4l_type_is_output(type))
> 
> Does the venus driver set sizeimage based on the given output resolution?

Yes.

> 
> E.g. if v4l2-compliance would first set the output resolution to 320x240,
> is the returned sizeimage value OK in that case?

Yes.

Here are few options to me:
 - set the correct resolution
 - set 0x0 and sizeimage at some arbitrary value (1 or 2MB). Despite if
the bitstream is 4K it will not be enough if the bitrate is huge.
 - invent some mechanism to trigger reconfiguration on the OUTPUT queue
as well (similar to the CAPTURE queue)

> 
> And this also means that the venus driver requires each buffer to have
> a single compressed frame, right? I.e. it can't be spread over multiple
> OUTPUT buffers.

I cannot say for sure but that is how all downstream cases uses it i.e.
one compressed frame per input buffer. I wonder if you fill input
decoder buffer with many compressed frames in one input decoder buffer
how you pass the timestamp for every packet?

> 
> We really need to let userspace know about such restrictions.
> 
> Stanimir, can you list the restrictions of the decoder for the various
> codecs?

What you mean? Restrictions like "one compressed frame per input buffer"?

-- 
regards,
Stan