Re: How to fix video files ?
- From: "Ken Maltby" <kmaltby@xxxxxxxxxxxxx>
- Date: Wed, 13 Jun 2007 16:17:07 -0500
"Scubajam" <jmcgauhey@xxxxxxx> wrote in message
news:1181753479.360695.146090@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jun 12, 9:04 pm, Chipcom <bz1...@xxxxxxxxx> wrote:
Hi
I need to know how to fix video files when the audio and the video are
not synchronized
Thanks
We need much more information to help you.
1) exactly what process has clip been through. Did it start as analog
converted to digital, and how; did it start as camcorder Firewire
capture to an avi file? All the details please.
2) What process have you used in editing, and what programs? Have you
changed formats, like starting editing an avi file, then convert to
mpg for DVD, then tried to edit that? These are just examples.
Exactly what you, or someone else, have done is very important.
One way of losing synch is working with mpg files. A very quick
possible solution is to just cut the file every minute or so. No
other edit, just a simple cut every minute all the way through the
file. Try this.
If you only have the final file someone else gave you, and it is out
of synch, that's more difficult. Maybe separate audio from video,
then change speed of video to match the audio. More complicated,
needs a good editor.
Let us know.
Jim McG
Washington State
Actually .mpg audio/video sync is probably the easiest to fix,
just run it through www.VideoReDo.com . MPEG muxing
maintains an exact relationship between the audio and video
streams. Tools like VideoReDo can work that, to easily fix
audio sync issues.
Where it really gets hairy is during transcoding where a
difference in the audio sample rate or other timing factors
causes a progressive change to the audio's playback rate.
(The sync gets further off, over time.)
Luck;
Ken
Additional useless trivia:
In terms of playback time, the MPEG audio frame is a
little smaller than the MPEG video frame. So a .mpg
file will contain more audio frames than video frames.
The streams in a MPEG file are usually interlaced (not
the same as interlaced video) with a certain number of
audio frames then a certain number of video frames.
(Some encoders let you set those parameters, although
I don't know what you can get from that.) In any case,
to playback the audio and video in sync, there has to be
a means to indicate where each audio frame fits in the
video frame playback.
Everything within a MPEG is coordinated by referencing
frame starting points. This means that the header of each
audio frame contains a reference to an offset from the
starting point of a particular video frame.
It's a relatively easy task, during transcoding or playback
(or with a tool like VideoReDo) to change those references.
[More really boring trivia:]
The way a DVD muxes the audio and video is a little
different, just to make things more confusing.
.
- References:
- How to fix video files ?
- From: Chipcom
- Re: How to fix video files ?
- From: Scubajam
- How to fix video files ?
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