I spliced together a phono cable into two of the four wires in an audio cable. I then plugged the phono end into the video output of my TV, and the audio jack into the microphone socket on my computer - so I recorded the information in the cable coming from the TV. I tried playing it back (by moving the phono jack to the video input socket and the audio jack into the headphone socket), but it didn't work. When I plugged it into the audio input of my TV I heard some weird noises (so I knew there was a signal leaving my computer).

Does anyone know whether this could work as a way of recording video (even if I was only storing it on my computer)?

 

Video is such a high frequency that I'm surprised you got anything in the audio range.

 

Video is such a high frequency that I'm surprised you got anything in the audio range.

If I was to use a static image would I be able to replay it on my TV?

 

No. The sweep frequency is the same whether the picture is holding still or not.

 

There are components in composite video that are at harmonics of the field rate. Of particular note, the vertical sync pulse is reliably at the field rate (50 Hz or 595.94Hz for broadcast in most places).

 

I spliced together a phono cable into two of the four wires in an audio cable. I then plugged the phono end into the video output of my TV, and the audio jack into the microphone socket on my computer - so I recorded the information in the cable coming from the TV. I tried playing it back (by moving the phono jack to the video input socket and the audio jack into the headphone socket), but it didn't work. When I plugged it into the audio input of my TV I heard some weird noises (so I knew there was a signal leaving my computer).

Does anyone know whether this could work as a way of recording video (even if I was only storing it on my computer)?

The Video (Composite) Out has signals from 50 (60) Hz to 5.75 (4.65) MHz depending on whether it is PAL or NTSC system.
In either case, the output will be a 1Volt Peak to peak which will overload your microphone input drastically.

If you intend to record the composite video, you will need an active interface to connect it to the PC.

Google for Video Capture Units or TV front ends for PC's.
Ramesh