On 2013-04-29, Dave Malham wrote:
Pretty certain it could be done with an ARM with C or C++ these days.
Yes, though the data rate of the incoming video stream is a bit steep (20-30MB/s), so that you need a rather muscular DSP to keep up, and you probably won't want to go the easiest way which would be to use some existing software to capture the uncompressed video and then write an offline program to decode it. I'm not too sure there are standard formats for uncompressed video which let you do reliable separation of specific scanlines either, which is what is needed here. And you definitely don't want the pain of working directly with the baseband video signal -- though the necessary SDR code might be included in GNU Radio or some similar toolkit, and theoretically you can ignore chroma.
However, it would still take quite a bit of work for a pretty small market. If it ever gets done it'll be by someone who is either (a) a masochist or (b) in desperate need with a pile of vital tapes and no pcm units available.
To me it seems getting the tapes accepted into some library's preservation program would be the easiest way to get the funding for the initial development. Or, perhaps Sony would be interested, given that there have to be a number of interesting and important masters out there which they could benefit from if (re)mastered.
There wouldn't be any problem with patents for the PCM units as they were first marketed 30 years ago which would put patent dates at 21 years or more so they would have expired - Dolby A (which was introduced in 1966), Dolby B (1968) and Dolby SR (1986) all fall into the same category.
That's distinctly easier because the formats aren't such a kluge, and if you just want to do one-time migration, your code wouldn't have to be ultra optimized either. (If you can just throw cycles at it, analog filters are easy to emulate with an evil enough oversampling ratio.) Level calibration could prove a bit of a challenge there, and there might be nastier restorative actions you might want to take at the same time, like locking onto bias phase, but otherwise it doesn't seem like rocket surgery to me.
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