Xpra: Ticket #2048: nvenc startup is slow - send replacement jpeg frame

Even with decent hardware and a single card, it can take ~200ms to initialize the nvenc context (some examples in #2022).

Just like we already do with delayed frames (r13047), we can send a jpeg before initializing the video encoder and then skip the first video frame that comes out of it (the client still needs to decode it but doesn't need to display it).

This will probably require a new "slow-start" codec attribute.

Mon, 19 Nov 2018 14:30:03 GMT - Antoine Martin: status changed

Because the video encoder initialization has to run in the encode thread, we would still incur a 200ms delay, but at least the first frame would arrive quickly. (more important when the window is locked on video encoding)

A smoother solution to this problem would be to:

Tue, 20 Nov 2018 13:45:43 GMT - Antoine Martin: milestone changed

I think that this can only work well if we move video encoding to a separate thread so that the normal flow isn't disrupted. We have to ensure that we don't update that video area with non-video screen updates, as those could arrive out of sequence. That's exactly what the video region exclusion code does... but video encoders can be used without video regions.

On the plus side, the "video-clean" code wouldn't have to wait for the encode queue.

Thu, 14 Feb 2019 05:42:16 GMT - Antoine Martin:

See also ticket:2113#comment:7.

The threaded initialization could use video_fallback until the video encoder sets a ready flag. This is_ready() encoder method could return an exception or error code if the initialization failed, otherwise we would need a callback so that the encoder can tell the window-video-source to try fail this encoder and try another one.

Another option would be to pre-allocate encoder sessions, but this would waste precious encoder contexts. Or maybe just pre-allocate the CUDA context, assuming that this is the most expensive part.

Wed, 20 Mar 2019 05:06:15 GMT - Antoine Martin: milestone changed

Milestone renamed

Fri, 17 May 2019 05:03:13 GMT - Antoine Martin: attachment set

"works" but cleanup causes a segfault

Sat, 18 May 2019 06:31:20 GMT - Antoine Martin: owner, status changed

Done in r22744 - details in commit message (minor related change in r22746)

r22745 makes it possible to test this code on "faster" cards that would initialize so quickly that we don't have time to trigger the fallback code:

XPRA_NVENC_SLOW_DOWN_INIT=2 python3 /usr/bin/xpra start -d compress,nvenc

@nathan_lstc: I think you will be interested in this. The stuttering should now be completely gone,

Sat, 18 May 2019 06:31:38 GMT - Antoine Martin: milestone changed

Tue, 11 Jun 2019 16:48:58 GMT - Antoine Martin: status changed; resolution set

Not heard back.

Thu, 13 Jun 2019 14:08:59 GMT - Antoine Martin:

r22932 fixup for the vpx encoder.

See also #2414, #2415.

Sat, 23 Jan 2021 05:40:46 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2048