[mythtv] tiny code improvement.

michael at optusnet.com.au michael at optusnet.com.au
Mon May 12 09:10:57 EDT 2003

Matt Zimmerman <mdz at debian.org> writes:
> On Sun, May 11, 2003 at 05:19:57PM +1000, michael at optusnet.com.au wrote:
> > #2. Mythtv is very slow to change position. Skipping forward
> > 30sec or 10 min can take 10's of seconds.
> Not here.  Have you investigated the root cause?  This is a good first step
> when trying to solve a problem. :-)

Trying to. I leave vmstat running in a window and hit page-up. CPU
utilization falls to zero, disk activity stops, mythtv freezes for
20 seconds and then continues. Want to take a stab at where you
think the problem lies? :)
> Are you running current CVS, or the 0.8 release?

> > #3. Mythtv doesn't cope which high bitrate data streams. Using
> > a 3 megabyte/sec video stream is enough to cause both recording
> > and playback to choke.
> A 3 megabyte/sec video stream is enough to cause most hard disks, some
> memory buses, some CPUs, and many networks to choke.  What has led you to
> believe that the bottleneck is mythtv itself?

vmstat says the CPU is 70% idle.  I can stream 15MB/sec read and write
simultaneously from seperate parts of a 20 gig file without
problems. Using mplayer I can happily decode a working recording
without burning more than 20% CPU. I'm using a hardware mjpeg
card for recording.

I'm reasonably confident the machine can take it.

Noting that if your memory bus, CPU or hard disk can't take 3
megabytes/sec, it's probably worth investing $50 and getting a
slightly more modern machine. ;)

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