Help! I frame distance and other optimizations

[casals]

When createing a VCD (or SVCD)

1. is there any standard specification on what the I frame distance should be for a VCD or a SVCD?

2. when I set a long I frame distance (i.e. 15 or bigger) i get a strange effect: in every cicle (untill the next I frame) the picture turns gradually to green!!, specially the areas with clear colors. It's specially easy to get it with a distance of 45, but also with arround 15. WHY?!? is there other solutions than setting a distance of arround 4? (I use cinelerra to encode the MPEG)

3. Is there an EXACT bitrate that an MPEG for a VCD should have? Is it enough with just keeping down of (but not being exactly) 1150 kbits/s?

thanks!

[vcd4ever]

casals;

I'm only encoding to vcd, so i can't help you with svcd questions. The answer to question 1 (vcd): The maximum distance between I-frames is 2 seconds..this is required by the CD-i app. The answer to question 3: The bitrate according to the vcd spec is 1150, but you can use a maximum bitrate of 1151.929 and this is supported by all players that can play vcd. This is the maximum bitrate the CD-i app will play.

Please note that it's mandatory to include the CD-i app when authoring a vcd..so if you want a vcd that's playable in all players that can play vcd, then you must include the CD-i app and follow the spec's as above.

vcd4ever.