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

[Mark Moriarty]

Transcoding is, by definition, required.
The reason is that timecode insertion is, "under-the-hood", the insertion of
subpictures that contain a bitmap of the timestamp into the individual
frames of the source video, blending them in.
You cannot do that kind of thing in the encoded video, you have to bring the
video to baseband, the source, raw, frames.  CODECs do some complex math on
the source video, normally a bunch of fourier transforms, plus things based
on preceding and following frames, in order to achieve compression -- no way
to add something after-the-fact, against the encoded video.
As to transcoding timestamp being bad in a file-file transform, good point,
though I'm not sure how easy to change that would be.  If I want a real-time
timestamp I run two copies of VLC, one the server doing the timecode
insertion, the second being a client that restreams the incoming video to a
new file.  This makes the stream real-time, with a properly stepped
timestamp.

-----Original Message-----
From: vlc-bounce at videolan.org [mailto:vlc-bounce at videolan.org] On Behalf Of
GALAD77
Sent: Thursday, March 10, 2005 6:58 AM
To: vlc at videolan.org
Subject: [vlc] timestamp in video while transcoding from file to file

Hello,

I'm trying to play a streaming input to a file, applying the -time filter
transcode option. The process works fine, but if I transcode from one file
(f1.ts) to another one (f2.ts) applying the time-filter option, the
resulting file (f2.ts) does not contain accurately the time label.
I think this is caused because vlc works 'as fast as it can'. So while
playing the file, each second the time is update; on the other hand, if
transcoding from file to file is .say, 3 times quicker, then the visualized
time label in the f2.ts is changed three times slower.
Is there a way to correct this issue?

I think the time filter is very useful, but it can only be applied with a
transcode option, which is very CPU consuming. Is there a way to play a
stream/file (that has no time-label) with vlc so that it inserts the
time-label without transcoding?
In this case, is it possible to indicate a time starting point, without
taking it from the system's clock (the source file could be dated a month
ago)?

Thanks,

G.   


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