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

Ian Grant mailinglists at iangrant.me.uk
Mon Apr 3 09:07:15 UTC 2006

Chris Pinkham wrote:
> Not sure who said that, but I know it's not what I told you in the thread
> you linked to. I said that I personally had fixed mythtranscode and
> NuppelVideoRecorder a long time ago to support specifying the proper
> aspect ratio in the nuv header. It works great for my transcoded
> recordings. My 4:3 recordings show as 4:3 when displayed in
> NuppelVideoPlayer and mplayer (with the patch applied) and my 16:9
> recordings show as 16:9 in NVP and mplayer.

That's the response from the DSMyth author that I quoted from the message 
boards for that over at SourceForge.

> Do you know if you can change aspect ratios in a mpeg4 stream? If so,
> and libavcodec supports it, then it should be easy to add, but I'm not
> sure if it is possible (but, I'm not a video expert either).

I know next to nothing about video, but from a bit of Googling, I think 
that it is possible:
Unfortunately they also suggest that very few players support this aspect 
ratio, so perhaps it would not work even if it were there...

> You were talking to one of them (ie, me) in the thread you linked to
> above. This isn't an issue for me, so I haven't got the itch to research
> it, but if you can find out, I can modify the mpeg4 transcoder to support
> it.

I would love to get this working [as I imagine/want it to work], but have 
no real skill to offer myself. I'm happy to help, test, etc., in any way I 
can, though. I don't know how many other people are experiencing the same 
problems, certainly I suppose it would not be a problem if I were using a 
normal Linux frontend.

I suspect it also requires some work on DSMyth, which is under development, 
but I think slowly.

I don't think the suggestion I quote of specifying a 16:9 resolution when 
transcoding (or adding black bars, if that were possible) is flexible 
enough, as the problem is particularly complex with DVB, where different 
programmes are transmitted in different aspect ratios and resolutions.


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