[Ffmpeg-devel] Wrong duration in a nut container

Michael Niedermayer michaelni
Fri Aug 12 10:31:00 CEST 2005


Hi

On Thu, Aug 11, 2005 at 10:05:58PM -0400, Rich Felker wrote:
> On Fri, Aug 12, 2005 at 01:14:35AM +0200, Michael Niedermayer wrote:
> > Hi
> > 
> > On Thu, Aug 11, 2005 at 02:47:03PM +0200, Hendrik Schmal wrote:
> > > Hello,
> > > 
> > > I want to grab a video from tape (via framegrabber (bt8x8), no audio, SuSE 
> > > Linux 8.2). I use the FFMpeg-20050806.tar.bz2 package.
> > > 
> > > The following commandline (see below) should give me a video containing 250 
> > > frames (that means 5secs on 50fps).
> > > 
> > > With the avi format I get a duration of 5 secs. The nut format shows me a 
> > > wrong duration, but it also contains 250 frames. 
> > > This happens when for example the tape partially contains no data.
> > > 
> > > The same behaviour I have using the FFmpeg API (libavformat/libavcodec).
> > > 
> > > I can't use avi, because of my videos are larger than 1GB.
> > > 
> > > Is this a bug or did I something wrong ?
> > 
> > nuts duration field is in a info packet and thats neither stored nor read
> > currently, patch welcome
> 
> IMO using the info field is a very bad idea. For instance people might
> framecopy a nut file to make a small excerpt, and keep all the info
> headers. Then the total length will be wrong. Instead the demuxer
> should seek to the end and read the last timestamps to find total
> length.. It will already be seeking to end to read index anyway, and
> if there's an index it can just get total length from the index.

and if the file is on something non seekable?
its a question which is more important, the validity of the duration
field in randomly cut raw pieces or the availabilty of the duration 
in non seekable streams

[...]
-- 
Michael





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