[mythtv-users] Transcoding and aspect ratio (DVB-T)
mailinglists at iangrant.me.uk
Mon Feb 27 16:47:51 UTC 2006
--On 27 February 2006 4:57 AM -0500 Chris Pinkham <cpinkham at bc2va.org>
> 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:
> 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.
I've tested this by making the modification you suggest, and when
GetVideoAspect() and SetVideoAspect() are called, 'video_aspect' is
correct, at 1.77778.
However, the resulting nuv file is still produced in 4:3 format.
I use Media Player Classic or VideoLAN Client to view the files, and both
are capable of forcing 16:9, but detect it as 4:3.
I also used nuvinfo to verify the aspect ratio in the file; for the
recorded mpg, it is 1.77778, for the transcoded nuv, it is 1.33333.
Any ideas as to where else it could be going wrong, and how I can test that?
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