analog video as an audio stream

[bakonfreek]

Is it in theory possible to convert an audio recording of an analog video signal to a digital video file without using a capture card? I already know that my TV can convert the audio to a picture when I plug the audio out from my computer to the video in on the TV, but I was wondering if this would be possible without the use of a capture card.

I did find that the higher I had the bit rate, sampling rate, and bit depth set, the better the picture came through. As well, having a louder file also made a better picture (until I ran into clipping which had some interesting effects).

No biggie if it's not possible, I am just a bit curious and I don't have work tomorrow so I was just messing with data streams.

[newpball]

Is it in theory possible to convert an audio recording of an analog video signal to a digital video file without using a capture card?

Think about it, the bandwidth of an analog SD video signal is somewhere between 4 and 6 MHz (depending on video system and version) now compare that to the bandwidth of an audio recording.

[bakonfreek]

It seemed to work on my TV, but it only works on my shitty Trinitron (I get nothing on my HD Vizio TV...no surprise there).

[pandy]

Is it in theory possible to convert an audio recording of an analog video signal to a digital video file without using a capture card? I already know that my TV can convert the audio to a picture when I plug the audio out from my computer to the video in on the TV, but I was wondering if this would be possible without the use of a capture card.

I did find that the higher I had the bit rate, sampling rate, and bit depth set, the better the picture came through. As well, having a louder file also made a better picture (until I ran into clipping which had some interesting effects).

No biggie if it's not possible, I am just a bit curious and I don't have work tomorrow so I was just messing with data streams.

Well - if you can expand time then yes, or if resolution like 1x576(480) suit your needs then answer is also yes.
Horizontal sync frequency fit in audio bandwidth.
Using 2 channels at the same time (and additional simple electronic) you may extend bandwidth twice... but still it will be limited resolution (maybe 3 pixels on 576(480) lines).

[Cornucopia]

Not only is it possible in theory, but that exactly what was done with the D2 video format (c.1987). It was a composite signal that was sampled as-is in time, just like an audio signal.
But as has already been pointed out to you, the sample rate necessary for doing this properly & with good quality is 13.5MHz* for SD video (luma) and 74.25MHz for HD (luma).

Scott

*Note that this is >280x the rate of digitizing audio!

[Brad]

Somewhat OT but since you seem interested in this sort of thing: with a 28Mhz capture card, a guy called happycube continues to refine software decoding of LaserDisc players' raw RF output.

http://forum.lddb.com/viewtopic.php?f=32&t=2671