*Untested* but from a Sansa Support e-mail (101016-000591),
They gave these parameters for divx5 codec.
Container: AVI
Video Codec: DX50 (divx5)
Bitrate: 987Kbps or lower
Resolution: 320x240
FPS: 29.970fps
Audio Codec: mp3 (mpeg version 1 layer 3)
Bit Rate Mode: Constant (CBR)
Channel: Stereo (dual channel only)
Bit Rate: 192kbps
Sampling Rate: 44100Hz
