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MythTV on AppleTV under Linux Ubuntu

 

 

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davilla at 4pi

Sep 8, 2007, 5:50 PM

Post #1 of 1 (4230 views)
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MythTV on AppleTV under Linux Ubuntu

I'm working on developing a mythtv frontend distribution running on
the AppleTV under Ubuntu Edgy.

See
http://forum.awkwardtv.org/viewtopic.php?f=23&t=167&hilit=&sid=bd94c51c9ef092d26d6d815933a9cdbb
for progress over the past few months. I'm running kernel 2.6.21.5
with several appletv specific patches. I'm about to migrate it to
2.6.22 with ck1 patches for better thread scheduling.

Bottom line is the results are quite promising but still not 100
percent solid regarding HD content decode. SD content is trivial.

Here's my issues;

I was running svn #13716 until a week ago. With this version HD
decode with nvidia was looking pretty good. Tickets 3690 and 3789
were the main problem issues. 1080i decode was running 50-60 percent
cpu, Xorg was less than 5 percent. The ffmpeg sync was painful but I
was working toward tracking down the problems.

The Zap2it -> SD migration forced me to update my backend to svn
#14374 which of course propagated a protocol change from 34 to 35. So
mythtv frontend on the appletv was also updated to #14374.

Now on the AppleTV frontend, HD content is not possible. The removal
of internal a52 to ac3 has pushed me over on cpu and both video and
audio are stuttering badly.

Now comes the fun part. I've disabled the internal ac3 and am using
external liba52 for audio decode. I've also pulled ffmpeg from svn as
well as mplayer for comparison games.

The results;
a) mplayer (xvmc) + ffmpeg using liba52 -> 1080i HD content plays
fine with less than 60 percent cpu and Xorg is less than 5 percent.
Slight audio stutters which should be resolved with 2.6.22 with ck1
patches.

b) mythtv (standard xvmc) + liba52 -> periodic video/audio skips, cpu
close to 100 percent. OSD is gray.

c) mythtv (standard ffmpeg) + liba52 -> good video, slight audio
stutters, cpu is about 88 percent. OSD is color. I suspect that the
slight audio stutters will also be resolved with 2.6.22 with ck1
patches.

I don't understand how c) mythtv with standard (ffmpeg) decoding can
perform better than b) xvmc assisted decode. This should not be
possible with HD content using the 1GHz pentium-m in the AppleTV.

Any suggestions about what is going on?

Also, I see that mythtv-vid branch has been merged into trunk. Since
I'm working on the bleeding edge, are there any issues regarding
pulling the current svn for frontend work or will I have to update my
backend too?

I try to keep my backend stable as it's a production box recording
2-4 shows a day from a dual pvr-150 setup connected to two dish
network DP311 and the dual tuner HDHomeRun for HD content from
off-the-air. Backend is 1.83GHz Intel Core 2 Due with 2.5TB of
storage so plenty of ponies here.

Just for comparisons, my other HD content frontend is a Roku HD1000.
Running MythRoku it always works without problems.

Thanks
Scott


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