Well, there are any number of ways to frameserve an MPEG stream as an AVI. Probably the easiest is to use FlaskMPEG with AviSynth's Premiere Plugins. This will make "Link to Avisynth" an option in FlaskMPEG's Select Output Format menu. Then hit "Convert" and up pops a box that has a text string...copy it into notepad and save, then use that file as the source AVI. Be sure to use the Multipass version of Flask, otherwise you cannot seek the AVI...each frame can be served only once in a forward sequence.
Again, that's the easiest, but not necessarily the fastest. Another option is to use Tsunami MPEG encoder (Japanese program, apply the English patch) to create an MPEG project file. Then use VFAPI converter to open the project file and write a small virtual AVI which is only a few MB. This little AVI will allow you to use a multi-GB MPEG stream as an AVI, fully-seekable and rather fast.
Best regards,
Floyd