See the IVTV "General HowTo":
... and the IVTV specifics regarding firmware:
For a PVR-150 you do NOT need v4l-cx2341x-dec.fw or v4l-cx2341x-init-mpeg.bin
The hotplug firmware directory may be different on different distributions. The firmware link above tells you how to find out where it is on your distro.
===== Stuff below this line may or may not apply to your situation =====
NOTE: IVTV hotplug did NOT work for me reliably on Debian SID running kernel 2.6.14-1-686. Check your /var/log/messages and/or /var/log/syslog to see if the same problem affects you. I had to comment out hotplug lines in the IVTV source code, recompile, and reinstall. Thus forcing IVTV to use the older non-hotplug method of loading firmware. YMMV. Here's what I had to do to disable hotplug, just in case you need to do the same.
Edit three files:
Find all the lines that look like this:
#if defined(CONFIG_FW_LOADER) || defined(CONFIG_FW_LOADER_MODULE)
...and replace each one with:
...then recompile and manually copy v4l-cx2341x-enc.fw and v4l-cx25840.fw to /lib/modules/. Symlinks to these files did NOT work from /lib/modules/. I had to actually copy the files.