[mythtv-users] Transcoding and aspect ratio (DVB-T)

[Chris Pinkham]

> I don't have a solution for mythtranscode, but I'm quite sure that
> MPEG4 does not support embedding the AR in the video, as is the case
> with MPEG2. When I want to convert DVB-T recordings to MPEG4 I do it

I don't know about the individual frames, but the nuppel container we
are using does support storing the aspect ratio.  I changed mythtranscode
and NuppelVideoRecorder a long time to preserve the aspect ratio of the
source material instead of using 1.0 as the aspect (which really meant
4:3).  I also changed the mplayer patch to use the true aspect ratio
from the .nuv file.

I've seen others report this, but it's not occurring for me and my
16:9 transcodes from MPEG-2 to MPEG-4 so I can't debug it.

If someone has this issue and wants to help debug, it would help if
they could add a line in mythtv/programs/mythtranscode/transcode.cpp 
to print out the aspect ratio from the player to verify that the
player is detecting the aspect ratio properly.  If you are using
nuvexport with mythtranscode, then that is an issue with nuvexport
since mythtranscode just presents raw frames to nuvexport and
can't pass the aspect ratio info in the raw video data.

If you are using mythtranscode by itself, then you could search
for "float video_aspect = nvp->GetVideoAspect();" in transcode.cpp
and add a line like this below it to verify the aspect ratio coming
from the player is correct:

VERBOSE(VB_IMPORTANT, QString("Original Aspect Ratio: %1").arg(video_aspect));

The transcoder just passes this video_aspect straight to the recorder,
so I'm not sure how it could be getting messed up in the transcoder,
so I'm thinking that the player isn't detecting the aspect ratio
properly for some reason but want to verify.

If someone wants to give me access to a recording that has this issue,
that would also help.

-- 
Chris