Re: [FFmpeg-devel] [PATCH v7 1/9] libavutil: add hwcontext_d3d12va and AV_PIX_FMT_D3D12

["Wu, Tong1" <tong1.wu-at-intel.com@ffmpeg.org>]

>Aug 29, 2023, 06:15 by tong1.wu-at-intel.com@ffmpeg.org:
>
>> +
>> +    /**
>> +     * Specifed by sync=1 when init d3d12va
>> +     *
>> +     * Execute commands as sync mode
>> +     */
>> +    int sync;
>>
>
>This is not needed, particularly in the public API.
>
>> +    if (download) {
>> +        ID3D12GraphicsCommandList_ResourceBarrier(s->command_list, 1,
>&barrier);
>> +
>> +        ID3D12GraphicsCommandList_CopyTextureRegion(s->command_list,
>> +            &staging_y_location, 0, 0, 0, &texture_y_location, NULL);
>> +
>> +        ID3D12GraphicsCommandList_CopyTextureRegion(s->command_list,
>> +            &staging_uv_location, 0, 0, 0, &texture_uv_location, NULL);
>> +
>> +        barrier.Transition.StateBefore = barrier.Transition.StateAfter;
>> +        barrier.Transition.StateAfter = D3D12_RESOURCE_STATE_COMMON;
>> +        ID3D12GraphicsCommandList_ResourceBarrier(s->command_list, 1,
>&barrier);
>> +
>> +        DX_CHECK(ID3D12GraphicsCommandList_Close(s->command_list));
>> +
>> +        if (!hwctx->sync)
>> +            DX_CHECK(ID3D12CommandQueue_Wait(s->command_queue,
>sync_ctx->fence, sync_ctx->fence_value));
>
>This is wrong. When downloading to RAM, the frames must
>always be available and fully downloaded by the time the function
>returns. Therefore, a wait must always occur.
>Since this is the only place where sync is used, better remove the
>option altogether.

There's another place where it's used. It's designed for API users to blocking wait every decoded frame.
In end_frame() call in d3d12va_decode.c. 

    if (ctx->device_ctx->sync) {
        ret = d3d12va_wait_idle(ctx->sync_ctx);
        if (ret < 0)
            return ret;
    }

That's why when downloading, you don't have to wait again if hwctx->sync is specified. The frame has already been blocking synced in decoding process.

But yes I agree it's not that needed. I'll remove the whole design in next version.

Thanks,
Tong


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