FAQ - harrypm/vhs-decode GitHub Wiki

Frequently Asked Questions & Answers

Q: How do I get started what do I need?

A: Here's the checklist

0. A Capture Solution CXADC or DomesDayDuplicator
1. VCR & Tapes (And its service manual if not visually clear test points)
2. BNC with 50Ohm Cable (Bulkhead, Pigtails to solder or clamp to signal & ground points)
3. Storage at least 1-2GB for every min of expected capture time.
4. Optinally an CRT with underscan or H/V delay (Brodcast PVM or better Trinitrons etc)
5. Basic Tools, and an modifyed flat head screwdriver tip for tape guide ajustment.

Q: Why does the colour look weird in ld-analyse?

It's a work in progress as currently, it combines the signal to the same effect as SOX commands so consier it experimental but good enough for the checking tool it is.

Q: Is this the best way to preserve analogue media?

A: While keeping originals is always recommended, the RF capture process involves capturing an exact copy of the original signal content now you need one capture device per signal so while it's simple you may depending on the investment of setup, need to do multiple captures, for example, VHS with HIFI video is one signal output and the HIFI audio is another, this is less of an issue for one signal formats like Video8/HI8 ware there is one signal RF signal point of capture containing all information.

Q: What are the costs compared to for example a 300-10k conventional setup?

A: It costs under 60-600USD depending on your level of setup you wish to invest in CX Cards are 20-35USD per card and basic tools/cabling is under 50USD depending on how low you need to go but 2 fully assembled DdD units can cost around 300USD each or more with current DE0-Nano inflation/availability issues in 2022.

As always storage costs are relative to the amount of media so 0.5-1GB per minute of permanent capture space needs to be calculated but 90min tapes FLAC compressed should fit on a 100GB M-Disk for example.

Q: Is RF capture like normal video capture?

A: No it's a little more advanced & simple, as your copying the whole signal stored as its being played back there is fewer worries if there is tape shedding or handling damage as if the data was fine on one run its stichable in post-editing.

Once you have made a capture setup and your workflow is in the order it's as simple as connecting to a signal, capturing a signal, 1 command decode, use ld-analyse, 1 command export video, simple as copy-paste edit command per tape.

Q: Does VHS-Decode produce a better picture than an AG-1980P/FS-200 with TBC on for example?

A: It does everything broadcast TBCs can do and more down to frame or even RF sample-level control as its non-real-time after the fact processing every single frame could be decoded differently if absolutely needed the best example of this is the --recheck_phase command witch on each frame makes sure the colour is correctly processed in simple terms with a small hit to processing speed.

As it's not just a baked as is a video file you're not stuck with a fixed quality level or fixed processing just the potential of the media format its self and magnetic condition you can re-decode until perfectly adjusted.

Q: Do I need a normal capture card or a conventional setup at all?

A: Essentially you dont even need a monitor for your VCR, with just a CX card can give you a full-frame live output of the composite signal, but practically if you can get your hands on a Sony PVM (or JVC's) it will make your life easier to check for VBI data and alignment and tape stability and servicing ease.

Q: I have hard white lines in my decodes what are these?

This could be sevral things:

1. Loss of Tracking

Solution: Visually adjust tracking and re-capture.

2. Weak RF Signal Output

Solution: Try increase gain or an 10-100uf 16v electroltic or polymmoer capasitor to the RF tap point.

3. Hard Dropouts

Solution: Tape can have magnetic loss, shedding or cloged heads if the latter then cleaning is all you can do alongside stiching captures and or stacking them after the fact.

Q: I have issues with RF captures with an monitor connected?

A: It's pulling too much signal, either add a capacitor 10uf to 100uf 16v in-line with your RF tap point is common practice or just disconnect all but the RF capture hardware.

Q: What about VITC Timecode and Subtitles/Teletext data?

A: If the signal portion is intact and or correctly recorded, VBI area data is 100% recoverable as decoding outputs the full 1135x625 PAL & 910x525 NTSC frame to work with any standard tools or FFMPEG can handle it (however ld-process-vbi will cover all of this in future updates) wiki information on this.

Q: Why does decode only run at 2-3fps on X86 hardware and 5-7fps on an M1 Max?

A: CPU & Cache speed are the main bias in terms of computing to processing speed this means today the more highly integrated systems like Apple's M1 silicone will currenly be the most effective hardware, but it's worth keeping in mind the software is nowhere near-complete nor extremely optimised.

However, this does not stop you from running multiple decodes and separate points on the RF capture on high core systems for the small extra post handling trade-off.

Q: Why is my expensive JVC Prosumer Deck so low SNR?

A: This is an interesting thing that needs more per model documentation JVC decks generally seem to have weaker raw RF output compared to Panasonic/Samsung decks.