Thanks for the suggestions, it's all very helpful. It seems like data streaming should be possible with a Cypress or FTDI module (FTDI can do 40Mbyte/s FIFO over USB 2.0 apparently). It will require some substantial hardware and software development, so let's see if I ever find enough time to materialize it
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Take a look at SDRs that have baseband inputs. If you mod the VCR to bring out the raw head signals (buffered using high speed opamps), it would simplify things since you won't have to get one that goes down to near DC, plus you can try all sorts of post processing to get better image quality than what the old analog electronics can achieve.
S-video does exactly that without having to tinker with the VCR. It outputs luma (Y) and chroma (C) separately so they can be processed independently. The SDR approach would only help with the chroma signal because it's QAM modulated onto a subcarrier above the luma frequencies, but you need some logic/circuitry to recover the phase from the burst pulse on each line. And the luma (Y) signal still needs real-time sampling because it's basically an oscilloscope signal of the pixel brightness. Effectively, this approach will only reduce the required analog sampling bandwidth a bit (since only the Y has to be sampled), which still requires 10s of Msamples/s.
Inputs: Audio L+R, CVBS and S-video.
Output: an MPEG-2 USB stream that can be opened directly with VLC, streamed to your HDD or whatever you like. No drivers or special software needed.
The on-chip digital encoders are a bit of a hit-or-miss (mostly the latter). The MPEG2 encoders usually encode to some low-bitrate DVB or DVD standard for convenience and won't let you adjust the bitrate or access the raw data. For archiving I would use h264 at a high bitrate, but do some processing (deinterlacing, geometry, maybe some other filters) on the uncompressed image, so it's important to get the raw RGB (or YUV) stream to the PC. There are modern versions of these transcoder boxes which record from HDMI into an mp4 format onto a USB drive (and can be used for example with an analog to HDMI upscaler), but they also offer little to no configurability.
In the past, the best quality sampler, especially for non-time based corrected signals like those from videotape was actually Sony's Digital 8 cameras which has Composite/S-Video inputs with a fire-wire output. Sony designed the sampling chipset with 4 line adaptive comb decoder for the composite video sources and also designed the PLL clocking with analog video tape in mind as they knew many bought these cameras just to sample video into their PCs.
That's interesting. I know they could play back analog Hi 8 tapes, but I wasn't aware the cameras could digitize the signal, or even have external video inputs. I might be able to borrow one from some old people, so I'll check it out
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Your TI TVP5150AM1 chip is a toy and it's crap. And don't even bother with an 9bit adc and crap 8bit output is you want to do effective picture processing.
That was just an example for the data transfer requirements and standards. A few bucks more for a better quality chip like the ADV7188 won't be a problem, but they all have the same type of data output bus. Also, what's wrong with an 8bit output bus? The encoding is still effectively 16bit per pixel (4:2:2), it's just transferred at double the rate of a 16bit bus and the USB FIFO thingies use 8bit anyway. Or are you referring to a higher pixel bit depth (HDR?) or no chroma subsampling (like 4:4:4)? That sampling quality doesn't make much sense for VHS and would be far beyond USB 2.0 transfer speeds.
I confirmed I have at least 1 home-made dev board remaining with 5v in, flex cable data out.
2-SVideo, 5 BNC connectors.
How much?
Basically like a WAV file, but at a much higher sample rate. They're very common when working with SDR.
Can these SDR boards stream about 30 Msamples/s continuously to a PC?