If you mean for dumping the raw disk image,
ddrescue can be of use if the hard disk is in bad shape, it does a much more thorough read of the disk than other tools. The raw image can then later be used with e.g
Isobuster to extract video.
Photorec is another tool that can extract video/audio from a raw filesystem, though that program works by looking for file headers so you may get chopped up MPEG streams and remnants of MPEG streams that have been previously deleted.
Isobuster by contrast, has knowledge about the filesystem and storage format so it can do a much better job as long as the DVR is supported. They're different tools with different purposes.
