theora - Nov 2010 - How to merge and cut theora videos, and how to synchronize sound?

Hello. Excuse me in advance for these dumb questions.

I used ffmpeg2theora to convert much videos. Now I would cut and/or merge them.
How can I do it?

Furthermore, in many cases the sound was desynchronized - I converted TS mpegs.
I tried to add the sync flag with bad effects. How can I manually delay /
anticipate sound track?

On 11/03/2010 10:57 AM, Lucas Malor wrote:
> Hello. Excuse me in advance for these dumb questions.
>
> I used ffmpeg2theora to convert much videos. Now I would cut and/or merge
them. How can I do it?
>
> Furthermore, in many cases the sound was desynchronized - I converted TS
mpegs. I tried to add the sync flag with bad effects. How can I manually delay /
anticipate sound track?
There are a few issues here.  As for the tools to cut, join, & merge Ogg
files, you'll want liboggz, which includes oggz-chop, oggz-join, &
oggz-merge.

As for the desynchronization issues with TS files, you may need a more
recent version of ffmpeg2theora, because, if I'm not mistaken, some
versions of ffmpeg were broken in relation to MPEG TS files.

I encode alot of these types of files (my MPEG TS files come from digital
television recordings) and routinely run into A/V sync problems with
ffmpeg2theora.

This is entirely speculation on my side, and I have no data to back it up, but I
wonder if my recordings contain errors due to interference during the broadcast
or something. The computer's tuner reports consistently 99% signal quality
for
whatever that's worth. Whatever the cause ffmpeg2theora doesn't seem to
handle
them well.

I reported it to the ffmpeg2theora developer many moons ago but nothing ever
seemed to happen.

Unable to find a fix on my own, I have since stopped using ffmpeg2theora and
switched to HandBrake [1] for encoding these files.

HandBrake doesn't support the Ogg container, which I prefer. I tried to use
ffmpeg to change containers but it gave me a cryptic message about timestamps
that I don't recall right now, and couldn't find a solution to online,
so it
seems that I'm stuck with my Theora & Vorbis stuff inside a Matroska
container.

HandBrake also lacks some other features that ffmpeg2theora has, but it has no
problems keeping the audio & video in perfect sync.

Some people have said it must be a bug in FFmpeg, then, but HandBrake also uses
FFmpeg and as I've said doesn't exhibit these problems.

I'm not sure what HandBrake does differently than ffmpeg2theora but, if
it's
true that the MPEG TS files do contain errors, then HandBrake is more robust in
handling them and ffmpeg2theora would do well to adopt that, I think. Part of
the "be liberal in what you accept; be conservative in what you send"
idea
because I would like to switch back to ffmpeg2theora some day.

[1] http://handbrake.fr/
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Basil Mohamed Gohar wrote:
> As for the desynchronization issues with TS files, you may need a more
> recent version of ffmpeg2theora, because, if I'm not mistaken, some
> versions of ffmpeg were broken in relation to MPEG TS files.
Unluckily I deleted TS files times ago.
I think I can use oggz-rip to extract video and sound bitstreams, insert a delay
to or cut the start of the oga file, and re-merge them.
The problem is: how can I manipulate in this way the oga file?

> I think I can use oggz-rip to extract video and sound bitstreams, insert a
> delay to or cut the start of the oga file, and re-merge them.
> The problem is: how can I manipulate in this way the oga file?
With a combination of oggz chop and oggSilence.

The last one is from oggvideotools.