Are there specs for keyframe interval?

[PNPman]

Hi All,
I believe i got the ideal behind keyframes. From what i've read they seem to be used as checkpoints for fastfoward/rewind and goto. I need to know if there is any rule defining how they are implemented.

I'm uncompressing a 29.97fps divx and virtualdub gives me a warning,
" No keyframe interval has been set. Players will take a long time to fast forward or rewind the output file"

I don't get an option to set keyframes when looking under compression>uncompressed avi.

So i gots a couple questions.
1- If i ignore the warning, when i re-encode the uncompressed avi and wav to svcd can i set the keyframes then?

2- does the keyframe interval need to be set to something specific dependant on the encoding (mpg1,mpg2,etc), 3:2 playback, or FPS (15,23,25,29) or can it be any value i want?

3- would you all have taken up converting video formats to something that would play on your standalone as a hobby, if you knew ahead of time all the time, work, and study it requires? 8)

[Darkbird]

With uncompressed AVI, every frame is a keyframe.

1 - Setting of keyframes for mpeg1 or mpeg2 video is not done quite as directly as it is for DivX. Keyframes for mpeg are "I" type frames which start every GOP (group of pictures). Normally there is one "I" frame per GOP. So, the size of the GOP determines the frequency of keyframes. The most often seen GOP size for 23.97 fps material and 23.97 material that has been 2:3 pulldown'd for playback at 29.97 fps is 12. The most often seen GOP size for 29.97 fps material without 2:3 pulldown is 15. In both cases the GOP interval works out to exactly half a second. Stay with these figures for GOP size and you will be DVD/SVCD/VCD compliant as far as GOP size.

With some capture setups you can capture with GOP's that have only "I" type frames. You would do that in order to have the highest quality material possible for editing and later re-encoding to video with a normal GOP setup.

2 - See answer for #1.

3 - Yes, I'm preserving something that has sentimental and/or entertainment value.