[Bug 312159] [NEW] mythfrontend should crop 1920x1088 video to 1920x1080

[Mike Hicks]

Public bug reported:

Binary package hint: mythtv

The broadcast standard for HDTV in North America (ATSC) is defined as
1920 columns by 1080 rows (lines).  However, a limitation of the MPEG-2
video standard is that a video must be encoded using blocks of 16x16
pixels.  1080 is not evenly divisible by 16, so the actual broadcast
format is 1920x1088 pixels -- the bottom 8 pixels get cropped off by the
playback device.  Mythfrontend doesn't seem to be doing this correctly.

Most TV stations just encode black in the bottom 8 pixels, but some use
a gray bar (my local PBS station, KTCA, currently does this).  A black
bar usually isn't noticeable, but the gray bar can be quite annoying
(note that this gray bar can also appear in transcoded video, so a fix
to mythtranscode to crop the video before scaling and re-encoding is
also necessary).

Another side-effect is that this can cause video to be scaled awkwardly
when being displayed on a 16:9 display, since the ratio of the raw video
is 16:9.06666...

Note that there is (or was) also a 1440x1080/1440x1088 format for 4:3
high-definition video, so any fix should probably just generically apply
to any video with 1088 lines.

I'm not sure what the story is in Europe or other non-ATSC regions, but
since this is a side-effect of a fundamental attribute of MPEG video,
the same issue probably exists there too.

---
[mike at no5][~]$ lsb_release -rd
Description:	Ubuntu 8.10
Release:	8.10
[mike at no5][~]$ apt-cache policy mythtv
mythtv:
  Installed: (none)
  Candidate: 0.21.0+fixes18722-0ubuntu1
  Version table:
     0.21.0+fixes18722-0ubuntu1 0
        500 http://us.archive.ubuntu.com intrepid/multiverse Packages
---

** Affects: mythtv (Ubuntu)
     Importance: Undecided
         Status: New

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mythfrontend should crop 1920x1088 video to 1920x1080
https://bugs.launchpad.net/bugs/312159
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