What are VHS Chroma Flaws? How to Fix Them?

[lordsmurf]

Most people have no idea what chroma errors are. It layman's terms, it's "red and blue yuck" on the tv screen. Often like a mist, sometimes as outright flashing obnoxious noise.

It's also commonly created in both digital photos and digital videos, when shooting in low light (or with high ISO). The camera sensor sees pixel noise instead of image. The color noise is a bunch of moving red/blue/green pixels on screen, almost like your video has been invaded by colored ants or termites.

• High-end JVC S-VHS VCRs and Panasonic AG-series S-VHS VCRs that contain a DNR/TBC can reduce or remove this noise. It's not the "TBC" but rather the DNR circuits (powered by the TBC) at work. This is why a normal TBC doesn't "clean" an image.
• There is also some advanced filter work you can do in the digital domain (VirtualDub and uncompressed AVI), but it's not as effective and clean of a process as hardware. The "Chrome Noise Removal" filter in VirtualDub is a popular one. Note that the default settings are strong, and it can give color blurs unless tuned down.
• And finally, the LSI DVD recorder chipset can remove chroma noise/errors during the MPEG pre-processing step. LSI is found in LiteOn, JVC, LG, Zenith, ILO-04, Ellion and some others. The JVC version combined JVC DNR tech with LSI tech, super nice job.

So, what does chroma noise look like? Compare before and after clips. All of these are between 4MB and 7MB each. The below MPEG files are best watched in VLC (remember to enable a deinterlacer in VLC's video menu for viewing), or authored/burned to a test DVD-RW/DVD+RW. (Note, you must be logged in as a Free Member or Premium Member to download the MPEG videos. Not already a member? Register now.)

These were post-processed in VirtualDub, combined with some NR filters in TMPGEnc. The only noise left in these files was also present in the source, which is some MPEG mosquito and occasional block noise. It takes about 25:1 ratio of time for this software process (25 hours to fix 1 hour of footage, on single-core CPU). Hardware is realtime, and is more effective too. Update: Modern dual-core and quad-core systems go a bit faster now, too.