[FFmpeg-devel] About xvmc_acceleration

[Gwenole Beauchesne]

On Fri, 13 Feb 2009, Reimar D?ffinger wrote:

> On Fri, Feb 13, 2009 at 09:59:04AM +0100, Gwenole Beauchesne wrote:
>> Is some xvmc_acceleration different than 2 used nowadays? I wonder because
>> I'd like to replace xvmc_acceleration by an hwaccel_id = {HWACCEL_ID_NONE,
>> HWACCEL_ID_XVMC, HWACCEL_ID_VAAPI, ...}.
>
> What exactly would be the purpose of this?
> I do not like having a global, user modifiable variable that exactly
> duplicates the information in pix_fmt.

On the other hand, the variable is already here, why not make it more 
useful in some other way?

> The XvMC case is just checking against two different PIX_FMTs,
> the codec-specific checks for VDPAU can be replaced by 1 or two pix_fmt

XvMC has only two PIX_FMTs, but VDPAU has 5, VA API has 8, DXVA will have 
at least 3. Will you want to check against each individual pix_fmt for the 
common code? Granted, there are cases where you will only need to check 
for a specific pix_fmt (in the codec implementation, typically).

> checks, too, and the stuff in the common code IMO would be much nicer if
> it used a check against a appropriately named flag, e.g.
> CODEC_FLAG_SKIP_DECODE (actually this should be used in the codec
> specific parts, too, where it is appropriate).

And where would this CODEC_FLAG_SKIP_DECODE flag added? Assuming/hoping 
the user won't forget about it in his initialization code? What would this 
mean specifically? Just to simplify the check in error_resilience.c and 
mpegvideo.c?

> Admittedly that assumes that the different API will mostly need to skip
> mostly the same parts of the code,

This would depend on the entry-point for the HW accelerator: VLD, IDCT or 
MoComp. Or do you only want to handle VLD case?