On 03.07.2022 15:19, Nicolas George wrote:
Timo Rothenpieler (12022-06-29):
The lavfi avdevice as it is right now can't output "special frames"
like hardware frames.
This patch makes the lavfi avdevice output wrapped AVFrames instead
of copying the actual data, greatly simplifying it in the process.
Thanks for the patch. I am not familiar with the hardware frame
infrastructure, but this patch makes the whole code much simpler, and
assumedly more efficient to boot. That makes it worth it for that reason
alone.
Make sure to take a look at the non-RFC version of this patch I sent.
It sadly is a bit more complex again, since wrapped avframes only work
for video frames after all.
But copying audio data is not nearly as heavy weight as copying whole
video frames.
Plus, there are no hardware-audio-frames.
If it also allows to use hardware frames, even in a limited or fragile
way, it is a bonus. I do not see how anybody could object.
I am not at all sure if this has some unexpected consequences.
It works just fine with ffmpeg.c, but it might be an ABI break for
potential library consumers?
I think the case can be made for both positions: on one hand, an
application should not assume a demuxer will output any kind of frame
and should be ready for wrapped AVFrame; on the other hand, devices are
special and somebody who uses a specific device on purpose may make
assumptions on its behavior.
I think this case is fringe enough that we can accept the break, at
least if the device only outputs normal frames by default, not hardware
frames.
Yeah, I'm also leaning in that direction.
And full proper implementation won't care what kind of packets come out
of it.
Plus I can't really think of any API consumer that'd possibly implement
a lavfi.c based device and then also hardcodes the assumption what kind
of packets it outputs.
So once the issue Michael discovered is ironed out, I'd be inclined to
apply it, after some more testing.
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