[Kdenlive-devel] Audio sync issue

Dan Dennedy dan at dennedy.org
Fri Feb 8 20:59:49 UTC 2013

On Fri, Feb 8, 2013 at 6:05 AM, el jefe delito <eljefedelito at gmail.com> wrote:
> Thanks for the help.
>> To the original poster, you need to provide a sample file, the project
>> settings, and the render settings in order to investigate.
> My Nikon clips are 1280x720 at 23.98 FPS so that's what I changed my project
> file to use.  I exported this at the H.264 setting with default values, and
> the output appears perfect.  However, I need a logo overlay / watermark and
> trying to do that in the original project, the KDEnlive editor wanted to
> composite that image with a specific video track; my video is edited and on
> multiple tracks so I thought it'd be easier to add as a new project (and
> yes, I'd lose some quality with the re-render).

Understandable, but for future reference you can also add the first
project to the second project as a clip. However, this H.264 profile
is a very poor choice for this because it is designed for distribution
not for editing because the GOP size (keyframe interval)) is set to
250 frames. At 23.98 fps, that makes the GOP over 10 seconds! That
will make seeking and thereby a/v sync more challenging. You should
use lossless for an intermediate file, and they are faster to encode
as well.

> Ok, so the first output looks great.

Are you referring to just image quality or also A/V sync? Does the A/V
sync look good in Kdenlive's monitors even after scrubbing or seeking?

>  The next run, new project, same
> project settings and using only the recently exported file and a
> transparent-background jpg, however, tells me at Render time that there are
> No Matching Profiles for the H.264 option — which should be the exact
> profile that I just used!  How can it not match itself?  If I use it

There appears to be a cosmetic bug here. In a fresh project, the first
time you open the Render dialog it defaults to the HDV group, and
indeed HDV is not compatible with 720p23.98 (according to MLT and
Kdenlive). This message should not apply to the H.264 render profile
as it has no restrictions like that, but I saw the warning as well
when I used your overlay project. So, there is some state bug that
makes the render dialog erroneously issue that warning.

> anyways, I get audio sync issues worse than ever.
> Attached are the two projects I've been working on (normal edit, and then
> where I just add the overlay watermark).  However, I don't have a short,
> decent clip to use to demo these sync issues so I'll have to shoot that
> later and send it in 10 hours or so.

Based on this info, I do not need the original camera clip because it
is the render output of the first project that is giving you a
problem. I have not yet been able to reproduce this. I am not trying
to use your complex first project because that would take some time to
recreate with my own assets, and it does not appear to be necessary.

So, I locate a 1280x720 at 23.98 clip in my library, add it a kdenlive
project with same settings, place it on a track by itself, and render
it with the H.264 profile. I check the output in a couple of players
including Shotcut (MLT-based) and Quicktime Player on OS X, both of
which are playing it with good sync.

I open your overlay kdenlive project and replace the clip that is on a
track with the output from the preceding step. I render that out using
the render settings stored in the project file you provided (dual pass
H.264). The A/V sync of that output is good as well checked using same

Can you reproduce the problem by simply placing a clip on a timeline
by itself, rendering that, make a new project, add the rendered clip
to a timeline by itself, and render that?
If so, can you reproduce it using one of the binary builds I provided
to this thread yesterday?

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