[Mesa-dev] 10-bit fbconfigs break most video players using VAAPI+GLX

[Tapani Pälli]

On 2/6/19 1:16 PM, Michel Dänzer wrote:
> On 2019-02-05 11:30 p.m., Marek Olšák wrote:
>> Hi,
>>
>> Video players request fbconfigs with these attributes:
>> GLX_RED_SIZE = 8
>> GLX_GREEN_SIZE = 8
>> GLX_BLUE_SIZE = 8
>> GLX_ALPHA_SIZE = 0
>>
>> Note that the values specify MINIMUM required component sizes, not exact
>> sizes. 10-10-10-2 satisfies the requirement and therefore glXChooseFBConfig
>> returns it first. Then video players choose the first config.
>>
>> There are many video players that have this issue. I guess they copied the
>> same code from each other.
>>
>> If we expose 10-bit or 16-bit formats, a lot of software will be broken.
>> Any ideas how to get out of this rabbit hole?
>>
>> My suggestion is to change the behavior of glXChooseFBConfig to return
>> 8-8-8 or 8-8-8-8 first if they satisfy the attributes and ignore the spec.
> 
> Deliberately violating the spec and diverging from other GL(X)
> implementations sounds like a bad idea to me.
> 
> We should help getting broken code fixed by identifying it and making
> suggestions.
> 
> 
> For code using glXChooseFBConfig, unless I'm missing something, a
> water-tight way to get a config which exactly matches a specific format
> is to specify all of GLX_RED/GREEN/BLUE/ALPHA_SIZE corresponding to each
> component's size, and GLX_BUFFER_SIZE corresponding to the sum of all
> sizes. The former and the latter have opposing sort orders, so only a
> single combination of R/G/B/A sizes should match all five of them.
> 

This is the main reason why 1010102 is still disabled in i965, there are 
still issues, even with ubuntu 18.10. It looks like gnome-shell version 
in 18.10 is too old (does not have the 'fix' which was essentially to 
disable 1010102), Xorg 1.20 seems to work ok with DefaultDepth 30 
though. I guess one way forward would be to expose 1010102 but start 
listing all problematic apps with 'allow_rgb10_configs=false' to drirc.

// Tapani