[Mesa-dev] Playing with display timing -- VK_MESA_present_period

Michel Dänzer michel at daenzer.net
Thu Jun 25 10:25:01 UTC 2020

On 2020-06-24 5:19 p.m., Keith Packard wrote:
> Michel Dänzer <michel at daenzer.net> writes:
>> I assume 2. refers to the case of a single late frame, where the
>> next frame hitting the original absolute target would result in a
>> second visible stutter. While writing
, it occurred to me that although a relative target time may avoid
>> that second stutter, the audio stream needs to adapt to the
>> visual delay, likely producing audible artifacts instead? It's
>> not obvious to me that would be an overall win. (The only other
>> way I can think of is to re-synchronize later frames to the audio
>> stream, but it's not clear that this is possible without either
>> producing visible stutter again, or de-synced audio/video for a
>> noticeable period of time)
> I think the idea is that the application would interpolate time
> values in the video stream to bring it back in sync with the
> expected time over a couple of frames. I think we could easily
> construct a demo which shows the difference and see what we think.

Such a demo could be very helpful!

> I think we could ignore the audio stream as a 16ms lag between
> audio and video shouldn't be a big deal; we handle that in real
> life quite easily as that's the lag you get at a distance of about
> 5m.

I suspect it may not be quite that simple, e.g. the brain may
compensate for the distance determined from vision. :) Anyway, it's
plausible that this can be ignored.

>> P.S. Have you more formally proposed a Vulkan extension in the
>> meantime? If so, could you provide a reference to that here?
> No. If I had, the IP restrictions with Khronos would prevent me
> from discussing it here in any technical detail.

Ah, didn't mean to put you in a difficult position.

Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: OpenPGP digital signature
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20200625/2d7d674a/attachment.sig>

More information about the mesa-dev mailing list