Summary

This is the VHS-Decode Wiki maintained primarily by harrypm ([email protected]), Inside this wiki and its pages, you will find technical guidance and notations for getting a signal out of VCRs, capturing original modulated RF signals off of tapes, and processing them into video.

Thanks to the developmental crossover CVBS or Composite Decode exists.

LaserDisk and CD Decode are also a thing!

Concept of VHS-Decode

VHS-Decode is an affordable and relatively simple way to create a real 1:1 copy of analogue tape mediums allowing complete "after the fact" broadcast level processing & manipulation with integrated full-frame software-based Time Base Correction.

Since the original signal is being captured your tape can be preserved today with all its original contents from visual to VBI area like subtitles and timecode and as this project evolves so can the quality and recovery potential of your media there is no re-capturing VHS-decode has taken the biggest issue out of the archival process the need for real-time processing and use of inflated and today outdated equipment.

The TBC Format

Originally developed for LD-Decode the .tbc format contains the full 4fsc (4x the sampling of source RF signal) video signal in digital component (In 16-bit greyscale values) chroma and luma are separated for tape decoding to allow more post decoding control, these files can be played with ld-analyse or GNU radio even, and easily encoded into standard video formats such as FFV1 for further use or standard archival.

As the media is decoded to the 4fsc composite standard the resolution potential including the non-visible area is fully available.

1135x625 For PAL (17727262 hz)

910x525 For NTSC (14318181 hz)

Current capture chains today look like the following:

The Hardware Chain

VCR/VTR/Camcorder -> Video/HiFi RAW RF Test Points -> Possibbly an 10-100uf Capasitor -> RF Capture Hardware -> 8-bit or 16-bit Samples -> RF Data File -> Software Chain.

The Software Chain

Video RF Data File -> FLAC Compression (Archive) -> VHS-Decode Demodulation & Time Base Correction -> TBC File -> Dropout Correction -> Metadata Export -> Video Generation -> De-interlacing Yes/No? -> 10-bit 4:2:2 FFV1 80~130mbps digital video file.

Audio RF Data File -> HiFi Decode -> Demodulation & Noise Reduction -> Software selectible output 24bit 192khz FLAC or WAV standard file.

Current State & Future

This project currently relies on the integrated control & signal tracking chips on VCRs that tracks the signal correctly for demodulation, however for well-tracked tapes, VHS-Decode's Time Base Corrector far surpasses prosumer level VCR decks such as an AG-1980P/NV-HS950.

In the future, It would be ideal to capture all head drum signals with a custom amp/capture board and then do full tracking and demodulation in software, but for now, refining an already tried and working system and increasing multi-format support is the clear priority.