MPEG4 Modifier

MPEG4 Modifier is a free, simple tool that will help you modify certain parameters of your AVI files without re-encoding the source video.

This extremely fast application is capable of changing the original aspect ratio, removing or adding packed bitstream, and even switching the order of the interlaced field, always without touching the quality of the original image.
As no encoding and decoding processes are involved in MPEG4 Modifier’s performance, this tool provides fast and accurate results without altering the quality of the source video file. All aspect ratio modifications are made at the headers’ level, leaving the MPEG-4 file intact. This program allows you to change the pixel shape and the display aspect ratio independently, allowing you to create either anamorphic or letterboxed video streams. Though it includes all the basic options for both PAL and NTSC, you can always customize your aspect ratio values.
Probably the most useful utility included in the simple program is the functionality that allows you to eliminate the packed bitstream that makes some AVI files jump every few seconds while played using certain video players (to achieve this, you will also need to use its User Data modifier).
An incorrect field order in an interlaced MPEG file may also cause viewing problems. MPEG4 Modifier allows you to change the order of the field order and place either the top field or the bottom field first.
MPEG4 Modifier can also be used as a command-line application.