[vlc] Re: timestamp in video while transcoding from file to file

[Mark Moriarty]

It's a reasonable suggestion, just that you still have to bring the video
down to raw, baseband, to make it happen properly.

Most (not all) CODECs do things based on other video frames.  In some cases
what they do is look at the differences in the video, from one frame to the
next; the output for a single frame is actually an encoded representation of
a piece of what has changed.  In some codecs there is actually a predictive
mechanism, spanning multiple individual frames, so it isn't even a case of
just looking at the last frame plus the current one.

Anyhow, at the end of the day the result is that you have to bring video
back to the raw, source, frames.  It might be possible to do some things a
bit more selectively, but it would likely take quite a lot of work to do
this.

The timestamp could be changed so that what is embedded does not have to be
the actual, outside, time, but allowed the user to choose an arbitrary
initial time/date.  It would take a bit of work, but is probably more
readily able to be done.  I'm not sure of the level of interest in having
this capability (either outside users or developers -- the change would take
some time to implement and test).

Triggering based on the frame counter would actually need a bit more work,
since you have to accommodate source video that has different frame rates.
PAL is 25, NTSC normally 30 (slightly less, but that's down in the mud), but
you can get a wide range of variation, anywhere from a frame every second or
two to many frames per second.

Good suggestion, just perhaps difficult.

-----Original Message-----
From: vlc-bounce at videolan.org [mailto:vlc-bounce at videolan.org] On Behalf Of
GALAD77
Sent: Thursday, March 10, 2005 11:13 AM
To: vlc at videolan.org
Subject: [vlc] Re: timestamp in video while transcoding from file to file


Hello,

thanx for the explanation.
I have one suggestion, but perhaps it is not adequate as I don't know much
about source code.
Just to timestamp appropiately, if transcoding is necessary, one may change
the time each 25 frames with a counter variable.
Would it be simple or does it affect too much code? I will try to look for
the it in the source code, but it seems a big project...

G.

-- 
This is the vlc mailing-list, see http://www.videolan.org/vlc/
To unsubscribe, please read http://www.videolan.org/support/lists.html