[rafalaos] “I think that MPG1 standard admits only one size: 320×240 and a bit-rate.”
Actually you can vary the structure almost as much as mpeg2. My mediapress card will do 720X480 down to 48X32 and it does 1×1; 4:3 or 16X9 aspect ratio. The format was in wide use predominantly in Asia 5 or 6 years ago for producing video cd’s but I don’t think it sees much use anymore. At that time blank dvd-r media was costing about $20.00 per disc and there was a big error margin. With the progress made in dvd software and the low cost of dvd discs it’s odd anyone is requesting it although you can email the files pretty easily. You could put a 90 min. movie at near vhs quality on a 750mb cd with it.
If your clients are really stuck on this format try googling mpeg 1 encoder, there should be a ton of freeware for it. Apple has never supported it from early on but instead pushed their own motion jpeg A and motion jpeg B (equally useless by todays standards).