[FFmpeg-user] Problem with concat at the stitch point!

[Oliver Fromme]

Colin Barnette wrote:
 > I have been using ffmpeg to encode videos of gameplay recorded with FRAPS.
 >  I encode the files to .avi at 11000k bitrate, all with the same settings.
 > I then use the concat function to stitch the files together.  This usually
 > is not a problem however a stitch point seems to have a problem in which
 > the dithering from frame to frame gets mangled and the picture becomes
 > blocky and strangely interpolated This continues for the rest of the video.
 > 
 > In this instance, the problem occurs precisely at the stitch point from
 > file 3 to file 4.
 > 
 > Is this behavior documented? Have I been somewhat clear in my explanation?
 >  I really am not sure what to do about this as I have tried to re-concat
 > the files to no avail!
 > 
 > Any clues or help would be very appreciated!
 > 
 > Thanks!
 > 
 > Here's an example of my batch script to first encode:
 > 
 > ffmpeg -i s7-1.avi -b:v 11000k 7-1.avi
 > ffmpeg -i s7-2.avi -b:v 11000k 7-2.avi
 > ffmpeg -i s7-3.avi -b:v 11000k 7-3.avi
 > ffmpeg -i s7-4.avi -b:v 11000k 7-4.avi
 > 
 > And the command I use to concat:
 > 
 > ffmpeg -f concat -i list.txt -c copy 7-Final.avi
 > 
 > And a portion of 'list.txt':
 > 
 > file '7-1.avi'
 > file '7-2.avi'
 > file '7-3.avi'
 > file '7-4.avi'

When I concatenate files, I use a different syntax:

ffmpeg -i "concat:file1|file2|file3|file4" ...

I don't know if that makes any difference, but it might be
worth a try.

Also, it might work better to concatenate the source files
first and then encode the result to 11000 kbps, i.e.:

ffmpeg -i "concat:s7-1.avi|s7-2.avi|s7-3.avi|s7-4.avi" -b:v 11000k 7-Final.avi

Finally, please make sure that you use a reasonably recent
version of ffmpeg (the version from git head if possible).
In particular, do not use any version older than 1.2.

Best regards
   Oliver

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