[Bug 92220] GL_NV_vdpau_interop partially available

[bugzilla-daemon@freedesktop.org]

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https://bugs.freedesktop.org/show_bug.cgi?id=92220

--- Comment #7 from Alex Deucher <alexdeucher@gmail.com> ---
(In reply to riaasm from comment #4)
> I understand that you can't enable a GL extension if there's no support for
> it in the hardware, but I think this specific GL extension doesn't require
> anything specific in the hardware. 

It does require certain hardware features, namely decoding to separate fields. 
That's why we only enable it on UVD 2.2 and newer.  Older UVD hardware only
supports decoding to a full frame.

> 
> From what I understand, the GL_NV_vdpau_interop extension needs to be
> supported in the driver, not in the hardware. In this Phoronix article
> (http://www.phoronix.com/scan.php?page=news_item&px=MTQ2NjY) it is mentioned
> that NVIDIA implemented support for this in their binary driver (not their
> hardware). So doesn't this mean that supporting this extension fully can be
> done by improving/expanding the implementation in the driver?

The hardware needs to support certain features to allow you to implement a
software extension.  E.g., consider tessellation.  If your GPU does not support
tessellation, it does not make sense to expose the GL extension since the
implementation would be done in software which is slow.  In the case of this
extension, we could implement support for older UVD versions, but it involves
an extra copies.

> 
> As for the field and frame issue, I don't really know much about that. But I
> do know that there's UVD2 and UVD2.2, which is often also indicated as UVD2.
> Is it possible that the "Early versions of UVD" that "did not support field
> based output" could be the UVD2 ones and the newer ones that work correctly
> are UVD2.2? Because being able to make that distinction could make it easier
> to figure out if this extension will likely work or not. 
> 

We know which parts support decoding to fields.  UVD 2.2 and newer.

UVD 1.0-2.1 (R6xx, RS780, RS880, RV770, RV790) - don't support decoding to
fields
UVD 2.2 and newer (RV710, RV730, RV740, evergreen, NI, SI, CI, VI) - support
decoding to fields

> I assume that Kodi will not work with the UVD2, but will work with UVD2.2.
> If UVD2.2 guarantees that VDPAU can be used, then that might be a good
> solution too.

We only expose the extension on asics that support it (UVD 2.2 and newer). 
Kodi already supports that by checking if the extension is enabled.  The issue
is what to do about older UVD versions that do not support the entire
extension.  All UVD versions support the part of the extension that kodi uses
with it's current default settings.

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