Re: [Mjpeg-users] DV analyzer tool / optimizing video rendering?

[Jonathan W. <jw...@ph...>]

> 	There is the possibility that the field order was set incorrectly
> 	by Cinelerra (it's happened in the past as I recall) and that you
> 	were correcting it after the rendering.

I have had some cases where the y4m stream coming out of cinelerra either
specifies the wrong field order in the y4m header or doesn't give any field
order (that is, flags the stream as progressive).  The most recent one of
these was over the weekend.  In this case the source was a non-commercial
PAL DVD and the y4m stream header from cinelerra specified progressive
frames - even through the frames were visually top-first and the DVD's MPEG
stream flagged the frames as top-first.  Using yuvcorrect was essential to
ensure a watchable result. :)

The other time I've seen a similar effect was with a non-commercial NTSC DVD
used as the source.  This was several years ago now, but my memory of that
situation was that cinelerra made mjpegtools think the material was
bottom-first when it was in fact top-first.  Having said that, this
particular work was done using a DV-format intermediate so the y4m stream
wasn't coming from cinelerra.  The DV intermediate was probably responsible
for the bottom-first assumption by virtue of the DV format being (AFAIK)
bottom first by definition.  I think I resolved this particular issue using
"-z t" to mpeg2enc, but I may also have used yuvcorrect instead - it's too
long ago.

Regards
  jonathan