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-   -   How to capture, decode Dolby Surround VHS tapes? (https://www.digitalfaq.com/forum/video-workflows/11066-how-capture-decode.html)

WestRGB 10-09-2020 06:26 PM

How to capture, decode Dolby Surround VHS tapes?
 
I have some commercial VHS tapes that I want to capture for personal use. Several of them contain audio encoded in Dolby Surround and Dolby Surround Stereo. I've been trying to research ways of capturing the highest possible audio quality from these tapes, but there are some gaps in my knowledge.

Here's what I think I know. Please correct and supplant as necessary:

Commercial VHS tapes mostly came in two flavours of surround audio. Both systems outputted line level stereo (L and R) audio from the VCR that was "unfolded" or decoded by a receiver, and then outputted to the speakers.

The first system was Dolby Surround, which was a passive matrix decoding technology. It outputted 3 discrete channels of audio (L, R, and Surround). Surround was a rear mono channel. This system also supported a phantom center channel by driving audio to both L and R channels.

Second was Dolby Surround Stereo, also known as Dolby Pro Logic, which was an active matrix decoding technology. It outputted 4 discrete channels of audio (L, R, C, and Surround). Again, surround was a rear mono channel.

My workflow:
JVC HR-DVS3U --> AVT-8710 --> Pinnacle 710-USB --> VirtualDub 1.9.11 on Windows 10

I understand that I could get an audio capture card and an old receiver with the appropriate Dolby decoders, but in the interest of simplicity I was hoping there might be a software decoder available?

Most of the information I've seen online is very outdated. Folks don't seem too interested in preserving old Dolby formats -- especially on VHS. I'm curious if anyone else has experience with this?

latreche34 10-10-2020 12:08 AM

There is no such thing called preserving old Dolby formats, The capture card should capture the audio fine since it's a 2 channel stereo with the encoded extra channels in it, once captured it's preserved for decades, The question is how are you planning on previewing the captures? on a TV/Receiver or computer monitor/powered speakers. Either way a physical encoder is a must to feed the speakers the appropriate channels, A prologic receiver or a prologic PC audio card. Not too sure if modern receivers are backward compatible with old multi channel technologies.

One advice, It is good to use a professional capture device that can capture audio at 24bit/48Khz, Consumer cards are capped at 16bit, for multi-channel signal you want the highest audio settings. Later on if you want to convert to a modern multi-channel format such as Dolby digital, DTS or Atmos doing it from a 24bit master file is a lot better.


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