I just added this to the first info post:
Supported input formats to producer
It may not be well known, but on Windows, producer can transcode any format you can play back with a DirectShow player (like Media Player Classic). This means you can directly encode .MPG, .WMV, .ASF, .D2V, .AC3, .AVI (uncompressed, compressed, XviD, DivX), .AVS (of course), and even .VOB files, as long as you have the DirectShow filters installed such that the files are playable in your DS media player of choice.
Of course, be aware that if your source has low enough bitrate to have compression artifacts, these are faithfully re-compressed. For instance, I transcoded a certain 1280x720p HDTV demo, which has plenty of blockiness and ringing problems, especially during scene transitions, all of it which was reproduced on playback of the RV9 clip
