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Message #00191
[Bug 312159] Re: mythfrontend should crop 1920x1088 video to 1920x1080
Thank you for helping to improve Mythbuntu by opening this ticket. The work required to resolve this ticket is too much considering the complexity of the issue / rarity of the problem / man power of the Mythbuntu team. With that being said,
if someone else could write a patch, we will do our best to see that upstream adopts a fix.
** Changed in: mythtv (Ubuntu)
Status: New => Won't Fix
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mythfrontend should crop 1920x1088 video to 1920x1080
https://bugs.launchpad.net/bugs/312159
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Status in “mythtv” package in Ubuntu: Won't Fix
Bug description:
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.
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[mike@no5][~]$ lsb_release -rd
Description: Ubuntu 8.10
Release: 8.10
[mike@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
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