[mythtv-users] 1920x1080 vs. 1920x1088 HDTV streams

Bernd Paysan bernd.paysan at gmx.de
Fri May 20 09:20:38 UTC 2005


On Friday 20 May 2005 02:07, Doug Larrick wrote:
> Bernd Paysan wrote:
> > The main difference is obvious when switching from ProSieben to HD1:
> >
> > 2005-05-19 22:41:44.184 AvFormatDecoder: Video has changed from
> > 1920x1080 to 1920x1088.
> >
> > Apparently the 1920x1088 mode is decoded fine, while the 1920x1080
> > doesn't.
>
> Interesting that you have a video that's 1080 lines high.  Here in the
> US all the "1080i" content that we have is actually 1088 lines, with the
> bottom 8 lines defined to be blank.  MythTV actually has special code
> that sets the output to 1080 lines if it is given a 1088-line video, to
> avoid a black band at the bottom, and avoid scaling when outputting to a
> 1080-line display.
>
> The macroblocks in the ATSC MPEG stream are 16 pixels high, which is an
> integer divisor of 1088 but not 1080.  A 1080-line video would imply
> that the macroblocks are 8 (or 4; unlikely) pixels high.  I can see this
> breaking a decoder or being beyond the capability of some system.

As far as I can see from other discussions about the ProSieben HD stream, 
it's really 1088 high, so the macro-blocks are 16 pixels, but it seems to 
tell the resolution is 1920x1080. Maybe that's even more confusing.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://www.jwdt.com/~paysan/
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