10 Jun
2011
10 Jun
'11
9:59 p.m.
Excerpts from Ralf Mardorf's message of 2011-06-10
19:24:54 +0200:
I went through this a couple of years back with pretty much the same
result. The general consensus round here was that it is not possible to
shrink a video to fit with an audio track. Instead you should stretch the
audio track to fit the video.
I ended up using Blender to edit the video into chunks and align chunks of
audio to fit as best as possible.
I don't understand why it is not possible to resize a video track. It
seems to me that dropping video frames is significantly easier
programatically than time stretching audio.
On Fri, 2011-06-10 at 18:57 +0200, Renato wrote:
Thanks Renato, I've played with that already and know the approximate
offsets, but that doesn't help much. I'm not sure screen recorders
typically can pause and resume, and even then it would be less than
optimal anyway due to the transcoding of both audio and video.
Also, to clarify, those offsets are constant but only appear beginning
at a certain point in the file, imaginary example: after 97 Minutes the
offset is suddenly approximately -9600ms. Hence shifting the offset of
the whole file doesn't help.
On Fri, 10 Jun 2011 17:58:46 +0200
Philipp <hollunder(a)lavabit.com> wrote:
> Hi,
> sorry for abusing this list for a mostly video editing question, but
I
> didn't find a proper list and knew that
we have some video people on
> this list.
>
> I'd like to fix some videos that have partially out of sync video
and
> audio, meaning that beginning at a certain
point in the video the
> audio is suddenly out of sync by a couple of seconds. There's no
> constant change, the delay seems fixed once it's there.
>
> I wonder how to fix such a thing. The files are xvid encoded videos
> and vbr mp3 audio inside avi containers. I thought it should be
> reasonably easy to cut and move the audio (re-encode if unavoidable,
> but I know it's in principle possible without) and put it back in a
> container, but I didn't manage.
>
> Can someone recommend a program/workflow that would allow this?
>
> I tried:
> - Avidemux: seems like actual editing is not what this program was
> written for, couldn't figure it out, but it seems close
>
> - openshot: couldn't figure out how to separate video/audio
>
> - kino: seems to only work with DV-files, apparently takes ages to
> decode the file, doesn't seem to be what I need
>
> - openmovieeditor: I figured it might work by dragging the file to
> both a video and an audio track, but I got extremely garbled audio
> output, no idea what's wrong
>
> - cinelerra-cv: Doesn't start. No error message, it simply shows no
> window, nothing. Well, it does something with the screen, but it
> shows nothing.
>
> - pitivi: Doesn't seem like it can play back the video. I can drag
the
> video to the tracks and it starts to draw
a waveform, I guess no
> video thumbnails because of: gst.ElementNotFoundError: pngenc
> Doesn't seem to be able to play the video.
>
> - kdenlive: would require me to install 30 additional packages,
total
> about 200MB, no thanks.
>
> I thought it would be a simple task, really nothing fancy. Seems
like
> > I was wrong.
> >
> > Regards,
> > Philipp
> >
>
> Hi, unfortunately can't give you a full solution, but only a hint: in
> mplayer with "-" and "+" you can adjust audio/video
syncronization by
> multiples of 100ms (maybe you cand do finer, but I'm not sure).
>
> maybe you could then somehow record the output to a new file? I don't
think so, assumed you can display the video without side effects
in a way, that you could 'record your desktop', than you only would be
able to record video, but AFAIK not audio.
An app like Cinelerra can separate the container's audio and video, but
using video apps on Linux can become a PITA ...
21.9 Improving performance
For the moment GNU/Linux is not an excellent desktop. It is more
of a server. Most of what you will find on modern GNU/Linux
distributions are faceless, network-only programs strategically
designed to counteract one Microsoft server feature or another
and not to perform very well at user interaction. There are a
number of parameters on GNU/Linux, which ordinary people can
adjust to make it behave more like a thoroughbred in desktop
usage.
21.9.1 Disabling swap space
21.9.2 Enlarging sound buffers
21.9.3 Freeing more shared memory
21.9.4 Speeding up the hard drive
21.9.5 Disabling cron
21.9.6 Reducing USB mouse sensitivity
21.9.7 Assorted X tweeks
21.9.8 Speeding up the file system
http://cinelerra.org/docs/cinelerra_cv_manual_en.html
... if the app after editing should make a container again, it can
happen that the old man became a voice like Mickey Mouse or the
beautiful woman is transformed to a Conehead. After 12 hours using all
resources of your computer you will know if the video is ok or not. I
nearly have forgotten to mention, that it also can happen that audio and
video get out of sync during this process ;). YMMV.
On my machine Cinelerra always 'worked' OOTB! On Philipp's it doesn't
run.
Regards,
Ralf
Thanks Ralf,
I had looked at the typical problems but they all mention error messages
while I get none:
-----
$ cinelerra
Cinelerra 2.1.5CV GIT::01dc4375a0fb65d10dd95151473d0e195239175f (C)
2010 Heroine Virtual Ltd.
External ffmpeg
Compiled on Mon Mar 28 20:17:50 UTC 2011
Cinelerra is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions. There is absolutely no warranty for Cinelerra.
-----
That's it, nothing else happens in the console and no visible window
appears, though an invisible does appear (I can tell from the reaction
of my window manager, it tiles the invisible window but nothing is
painted there).
I thought cutting and aligning audio/video on a timeline would be a
basic operation and possible in every NLVE...
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user(a)lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-user