[mythtv] Making Squished 4:3 -> 16:9 again for mytharchive DVDs?

Nick knowledgejunkie at gmail.com
Wed Oct 4 08:44:39 UTC 2006


On 04/10/06, Paul Bailey <bailey at dreamshake.net> wrote:
>
> On 3 Oct 2006, at 11:49 pm, Jay R. Ashworth wrote:
>
> >
> > I'd be flat *amazed* if you ended up with a 4:3 scope recording
> > off-air, BTW: how did you manage that?
> >
>
> I might be wrong, but I think that's how widescreen SD DVB-T is
> transmitted in the UK.  For example, on playing back one of my
> widescreen recordings in MPlayer I see:
>
> Starting playback...
> VDec: vo config request - 720 x 576 (preferred colorspace: Planar YV12)
> Could not find matching colorspace - retrying with -vf scale...
> Opening video filter: [scale]
> VDec: using Planar YV12 as output csp (no 0)
> Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
> SwScaler: BICUBIC scaler, from Planar YV12 to Packed YUY2 using MMX2
> VO: [macosx] 720x576 => 1024x576 Packed YUY2
> [Mixer] No hardware mixing, inserting volume filter.
>
> If that is indeed what is happening, it's a *very* common occurence
> on my system, probably 75% of what I record is SD widescreen.

That's how it's broadcast - the MPEG stream contains a flag that
determines whether the video is transmitted/decoded as standard 4:3 or
widescreen 16:9 - whatever the actual resolution of the video. Common
sizes are 720x576, 704x576 and 544x576, and its the shape of the
pixels, not just the dimensions of the stream, that are important.

If MythArchive uses dvdauthor under the hood, it shouldn't be a
problem to account for this, as the XML format dvdauthor uses can flag
a video as widescreen during the DVD authoring phase. From the
dvdauthor manpage:

<video [format="ntsc|pal"] [aspect="4:3|16:9"] [resolution="XxY"]
[caption="field1|field2"] [widescreen="nopanscan|noletterbox"] />

Manually configures the video parameters for this pgcgroup. If any of
these are not set, then they will be inferred from the source stream.
Note that the DVD format only specifically supports 720x480, 704x480,
352x480, and 352x240 resolutions for NTSC, and 720x576, 704x576,
352x576, and 352x288 resolutions for PAL, but DVD author will accept a
wider range of inputs and round up to the nearest size.

There have been a couple of widescreen capture-related posts on the
-users list also, so this seems like a popular topic at the moment.

Cheers,
Nick

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