Audio 3-4 frames out of sync in timeline

[Dan Dennedy]

On Thu, May 21, 2020 at 5:11 AM Massimo Stella <maxstar at tin.it> wrote:

> Hi Vincent,
> I'm glad you tried out Flowblade and Shotcut, because all these
> applications, Kdenlive included, are developed on top of a framework called
> MLT: https://www.mltframework.org/
> The developer of Shotcut is actually the same person who is developing MLT


Kdenlive developers help quite a bit with MLT as well.


> ----Messaggio originale----
> Da: vincent at hitcom.nl
> Data: 20-mag-2020 22.52
> A: "kdenlive"<kdenlive at kde.org>
> Ogg: Audio 3-4 frames out of sync in timeline
>
> Hi everyone,
>
> Whenever I playback video with audio in the timeline, the audio lags
> behind. To test this, I created a beep sound and a white color slide (both
> with a duration of 2 frames) and put them on the same spot in the timeline.
> All the other videos I edit have a fixed framerate but have the same
> problem.
>
> When I render the video, the sound is in sync. Only preview playback in
> Kdenlive lags. On a sidenote: Flowblade and Shotcut have the same issue.
> Has anybody experienced this? And were you able to fix it? I used a scaled
> down (360px) project monitor for smooth playback.
>

Some Shotcut users complained about the same thing, but I did not reproduce
it. They had to advance distinct audio clips that were manually aligned in
preview by a few frames. Audio and video output on some systems are often
out of synchronization because these signals take quite different paths
through the computer and out. And when outside the computer, they may go
through different devices that each have their own delays: for example, TVs
used as video monitors and/or audio receivers. There needs to be a way to
calibrate your playback system. This is being added for the next version of
Shotcut based on a MLT change to add a video_delay parameter:
https://github.com/mltframework/mlt/commit/ca017a12a04d3693668464e3ba9ad4e1ba24fabc
So far on my systems, I have only needed to make very minor adjustments,
and the jury is still out on whether this completely solves the problems. I
can give you a link to a nightly build in portable tar format if you want
to test it.
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