[mythtv-users] Mythexport sssssllllllloooooooowwwwww

Diego Torres torres.diego at ttcpl.com.au
Wed Sep 1 08:14:09 UTC 2010

Thanks mate, that was it... sort of.

I added '-threads 0'  and that made all four cores to be utilized.
At first I realized that there is a "multiple threading" checkbox on  
myth export and used
that . But it adds '-threads 2' to the command so it only uses two  

With '-threads 0' on both passes it only took 1.5 hours for the first  
pass and 1 hour to for the second pass.
Still not as fast as Airvideo but a heck of a lot faster than before.

The only things I noticed are:
- The 1 GB RAM was being used with the SWAP going to 200MB or so. I  
upped the memory to 2GB and it still used it all but did not use swap.
- Even though all 4 cores are being used, none are used more than 80%  
and there is always one that
oscillates between 30 and 80%. With Airvideo all 4 cores are pretty  
much pegged at 80% the whole time.
- I am  guessing that the CPU does not go to 100% because of I/O  
bottlenecks. It could be that the 500GB IDE HDD /controller combo
just can't keep up with ffmpeg using all four cores.
- The output file is twice as big as Airvideo's so there is definetely  
a mismatch on the settings. I need to investigate that.
- I realized that myth export uses a two pass approach whilst Airvideo  
uses a one pass approach
(because the output file starts to fill up immediately).  Doing some  
reading on the ffmpeg lit it says that a two pass
approach is required with a Variable Bit Rate and in general is  
recommended for quality output.
I reckon the quality from airvideo's one pass is more than good for  
the ipad so I will try hacking the script (time permittiing) to do a  
one pass only
and compare the conversion time.

Cheers and thanks again.


On 01/09/2010, at 2:41 AM, John Baab wrote:

> On Tue, Aug 31, 2010 at 4:36 AM, Diego Torres <torres.diego at ttcpl.com.au 
> > wrote:
> Video conversion is a slow process in general, especially if you are
> using h.264.  You can try adding "-threads 0" to your ffmpeg line in
> the config, which should make ffmpeg attempt to automagically detect
> cpu settings.
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

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