On 19 Aug 2003, Florin Andrei wrote:
> I believe i'm experiencing the "juddering" bug:
>
> I use a NTSC DV camcorder as a source, and convert the DV .avi into
> DVD-compatible MPEG2 using mpeg2enc as the last step. Then i author the
> DVD, burn it...
> Apparently the DVD is fine, i can play it with software players with no
> problems whatsoever. But if i play it in a standalone player to a TV, i
> experience "juddering", the moving objects are doubled and flickering
> fast.
>
> It seems like it's a "bottom first" video stream (see image0 and
> image1), but otherwise it's ok. I checked it out for the next thousand
DV is bottom field first. No other order is specified in
the standard (and interestingly enough this true for both
PAL and NTSC - wonder how that happened ;))
> of frames or so, the order of the fields is fine, there's no back and
> forth movement, it's all smooth and as it should be.
If you're seeing the juddering problem then something in the
tool chain between the capture and the encoder is flipping the
field order (or losing track of the order).
> However, i don't know how to analyse the MPEG2 file. I cannot apply the
> method from the HOWTO, because the intermediary YUV stream is not
> generated through mjpegtools; mpeg2enc (which was used to encode the
Hmmm, perhaps generating the YUV stream with a different selection
of tools might solve the problem...
To analyse a MPEG2 file I've found the 'dvdview' program to
be very useful. dvdview (and the required library) can be found
at http://rachmaninoff.informatik.uni-mannheim.de/dvdview/
The program has a debug/log capability - specifying higher levels
of logging will yield the field order.
> Suggestions?
Use DVD-RW or DVD+RW media to avoid coasters? ;)
Look at the YUV4MPEG/YUV stream after each step of the pipeline,
the 'Ib' tag should always be present - if it changes to 'It' or
'Ip' you've found the program that is changing the field order.
Steven Schultz
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