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Output filters to resize HDTV to SD on the fly
http://forums.linhes.org/viewtopic.php?f=15&t=17440		 Page 1 of 1
Author:  arnie [ Tue Dec 18, 2007 6:41 pm ]
Post subject:  Output filters to resize HDTV to SD on the fly
Hello all.

I've searched the forum but have come up empty. What I want to do is set up an output filter to down-scale HDTV content to SD resolution on the fly. I have a MythTV box that's only got a 1.8GHz CPU, so it won't handle HDTV, but I figure if I down-scale the image first, it might be able to display it.

I've had a look at the MythTV WIKI to see how to configure output filter chains, but there doesn't seem to be a resize filter. If anyone has configured this in the past or knows of a way to do this, I would appreciate a nudge in the right direction
Author:  tjc [ Tue Dec 18, 2007 8:35 pm ]
Post subject: 
Video playback should automatically scale on it's own. For example I have played various HDTV samples with resolutions up to 1080i back on a SDTV at 640x480 without any special fiddling.
Author:  grante [ Tue Dec 18, 2007 9:30 pm ]
Post subject:  Re: Output filters to resize HDTV to SD on the fly
arnie wrote:
Hello all.

I've searched the forum but have come up empty. What I want to
do is set up an output filter to down-scale HDTV content to SD
resolution on the fly. I have a MythTV box that's only got a
1.8GHz CPU, so it won't handle HDTV, but I figure if I
down-scale the image first, it might be able to display it.

I've had a look at the MythTV WIKI to see how to configure
output filter chains, but there doesn't seem to be a resize
filter. If anyone has configured this in the past or knows of a
way to do this, I would appreciate a nudge in the right
direction


You don't have to do anything. The player will automatically
scale the video to fit the output screen size/resolution.
However, it's still got to decode the HD before it can scale
it, and 1.8GHz probably isn't going to get there without XVMC.
Author:  turpie [ Tue Dec 18, 2007 11:37 pm ]
Post subject: 
As the others have said MythTv is already trying to downscale on the fly and if your system isn't fast enough there isn't much you can do other than upgrade (or try XvMC).

However if you can put up with "record now, watch later" you could set up a transcoding profile to resize the recording to SD resolution. The transcoding might take a while but your CPU should be able to cope better with the resulting file.
Author:  novellahub [ Wed Dec 19, 2007 8:52 am ]
Post subject: 
tjc wrote:
Video playback should automatically scale on it's own. For example I have played various HDTV samples with resolutions up to 1080i back on a SDTV at 640x480 without any special fiddling.


Ditto for me. I am playing back full HDTV recordings and outputing them beatufully via s-video to older tube tv. No adjustments had to be done.
Author:  arnie [ Wed Dec 19, 2007 7:56 pm ]
Post subject: 
I thought playback would automatically scale down, but when I watch a HD channel I get frontend errors about 1440x1080 is not a supported resolution and the screen turns blue.

I guess I'll have to do the transcode thing, but I won't be able to cut out the adds before transcoding like I do for SD streams.
Author:  tjc [ Wed Dec 19, 2007 8:07 pm ]
Post subject: 
You need to restrict the allowed resolutions in your /etc/X11/xorg.conf file to the appropriate PAL sizes for your TV.
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