[vlc-devel] [PATCH 02/26] vout: create/release the decoder device when the window is enabled/disabled

Steve Lhomme robux4 at ycbcr.xyz
Tue Sep 24 10:49:37 CEST 2019


On 2019-09-24 10:47, Rémi Denis-Courmont wrote:
> Hi,
> 
> Again, it would be nice if the underlying assumption, that NVDEC (and any other future extra hw decoder) was permanently a superset or subset of DX and VA.

I'm preparing a (longer) reply to that as we're going to have to take a 
technical decision and how (and why) we want to handle the decoder + 
decoder device + display mix. All of which that can be set by the user.

> I doubt that will work in reality. They are developed by different companies with different agendas and schedules.
> 
> Le 24 septembre 2019 09:55:59 GMT+03:00, Thomas Guillem <thomas at gllm.fr> a écrit :
>>
>> On Mon, Sep 23, 2019, at 18:50, Rémi Denis-Courmont wrote:
>>> Le maanantaina 23. syyskuuta 2019, 11.29.23 EEST Steve Lhomme a écrit
>> :
>>>> It's like the display module, it's treated as a resource that is
>> created
>>>> on demand by the decoder. In the past we need a display module to
>> create
>>>> the decoder/VA (depending on the display pictures). Now the VA
>> needs a
>>>> "decoder device" (the hint) before it's created.
>>>>
>>>> It's true that most decoders (ie not lavc or nvdec) will not need a
>>>> decoder device at all. And I agree we should not create it for
>> those.
>>>
>>> On-demand creation avoids the delay and resource usage for software
>> decoder.
>>> My problem is, now that NVDEC is added, we no longer have a "static"
>> choice of
>>> decoder device on a given system - NVDEC competes with DirectX and
>> VA/VDPAU.
>>>
>>> This potentially breaks the whole idea of creating the decoder device
>>
>>> (exclusively) from the window. Or NVDEC needs to permanently remain a
>>
>>> functional superset of DirectX and VA/VDPAU...
>>
>> We can still disable NVDEC on Windows by default since DX11 should
>> cover most of the need.
>>
>> For Linux, I don't see the problem. There will be one VAAPI and one
>> NVDEC decoder device that will be loaded just after the window. Only
>> one will be able to load depending on your main GPU/Display/Driver.
>> Therefore, the avcodec VAAPI va or NVDEC decoder will be automatically
>> loaded according to that decoder device.
>>
>>>
>>> -- 
>>> レミ・デニ-クールモン
>>> http://www.remlab.net/
>>>
>>>
>>>
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> 
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