[TriLUG] Troubleshooting dropped frames with firewire and dvgrab

[Ed Hill]

Hi Tom,

I have a vaguely similar set of hardware:

  - Sony Handycam HC20
  - AMD Athlon XP 2500+
  - 300GB SATA hard disk (using on-board Via controller)
  - generic PCI firewire card with a Via chipset

and I get occasional dropped frames but not as badly as you describe.
As you suggest, it could be a bandwidth issue.  Or it could just be a
lousy combo of firewire chipset and driver.  You can test/inspect your
hard drive performance and settings with hdparm:

  man hdparm
  hdparm -I /dev/hda
  hdparm -t -T /dev/hda  [although be careful with this]

and you can try running simple tests such as

  dd if=/dev/zero of=/path/to/some/file_on_disk_hdX count=2048 bs=1M

to see what sustained write speeds your system can do and then compare
that with the data rates generated by the dvgrab runs.  Most likely the
hard disks and the Linux VM, etc. can keep up...

I'd think about getting a different firewire controller with a different
chipset (since they are around $20 for a PCI card) or perhaps trying a
different kernel.  The firewire drivers/subsystem in the Linux kernel
have a reputation for being somewhat flaky -- at least thats what I've
read.

Ed

ps - Your IDE drives are each on separate channels, right?  From 
     the names you sent (/dev/hda and no /dev/hdb listed) that 
     appears to be the case but I just wanted to check.  Putting
     two IDE drives on the same controller can really kill IDE
     performance but you probably knew that already!  :-)

-- 
Edward H. Hill III, PhD
office:  MIT Dept. of EAPS 54-1424;  77 Massachusetts Ave.
             Cambridge, MA 02139-4307
emails:  eh3 at mit.edu                ed at eh3.com
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phone:   617-253-0098
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