[mythtv-users] NUVExport slow export solution

[Eric A. Cottrell]

Chris Petersen wrote:
>> nuvexport gets the output of transcode, parses it, reformats, and 
>> prints it on the screen.  It appears if the framerate gets over 20 FPS 
>> then nuvexport can not process every status line guickly.  The stdout 
>> buffer fills thus stopping transcode until it empties.  Reading the 
>> transcode man page I came across the --print_status option in 
>> transcode.  I modified the transcode.pm file in nuvexport to add a 
>> --print_status 4 option in the transcode command line.  This tells 
>> transcode to only print a status line for every 4 frames processed.  
>> This fixed the problem and increased the rate back to a peak of around 
>> 50 FPS when using nuvexport!
> 
> 
> I've added "--print_status 16" to the transcode options -- even 4 frames 
> is probably overkill.

I suppose that will work as well.  I wanted a value that would update a 
couple of times per second in case it slows down.

> And am open to suggestions about how to do something similar with ffmpeg 
> (nuvexport will soon be using ffmpeg for just about everything, since 
> transcode doesn't seem to work with a bunch of mpeg type files), or even 
> just speed up the buffering in nuvexport.  In my tests with the mp3 
> encoder, my settings were pulling 80-100fps, which I figured would be 
> fast enough; apparently it doesn't carry over to the other encoder types.
> 
>> I also noticed nuvexport will still use the -Z option when the output 
>> resolution matches the input resolution.  Transcode will still do zoom 
>> when the -Z option is specified with no change in resolution thus 
>> slowing down the frame rate for nothing.
> 
> 
> Yeah.  I apparently gave too much credit to transcode.  You don't happen 
> to have a patch for this, do you?
> 
Unfortunely I am not a perl programmer so no patches.  I have figured 
out enough to comment sections out or add strings.  I am a C++
programmer that develops in Windows.  In exchange I get money to buy 
computer parts and build Linux computers.

>> Since my computer has a HT cpu I uncommented the option to specify the 
>> number of CPUs in the transcode.pm file and gained about 1 FPS.  I 
>> noticed the first parameter for this option defaults to 10 but the 
>> code in transcode.pm set it to 100.  I used 10 and even tried 20 with 
>> no change of framerate so I left it at 10.  I assume 100 would be 
>> overkill and may even slow it down like the comment indicated.
> 
> 
> Interesting.  On my dual athlon, I found the exact opposite -- about 
> 1.5-3 fps slower (nuvexport has multi-cpu detection included, but 
> deactivated).  Since transcode encodes both audio and video in separate 
> threads, the kernel sends those to separate CPU's (which is what HT 
> works as in this case).  Creating another encoding thread just causes 
> them all to fight for resources on the lesser-used cpu.
> 
> Wouldn't be hard to add a commandline option to optionally enable this 
> (since it would definitely help for something like a dual-xeon box)

Sounds like a difference between Athlon and Pentium that either the
operating system or transcode does not take in account.

Several months ago I got a Philips DVP-642.  I want to convert my
saved programs to a mpeg4 format that is playable on the Philips.
I figured out settings that gave good quality on the computer but
so far anything I try using xvid is not playable on the Philips.
It seems other people have this problem as well.  I burned a movie 
trailer from the divx site and it played okay.

Most of the How-to information about xvid seems geared to windows users. 
  I recently discovered the xvid4conf program for linux.  I am getting 
stuff together slowly and may even write it down to help others.  There 
are several pieces that need to be setup for it to work.

NUVExport is a very useful program.  My main usage is when I archive 
shows I use it to get show information so I know what files to move.  I 
want to use it for converting files to MPEG4 format.

73 Eric