AVI, full name is Audio Video Interleave. It is technically stand known as a multimedia container format and was introduced by Microsoft in 1992. Being a multimedia container format, AVI files can include both video and audio, allowing synchronous playback.Most AVI files also use the file format extensions developed by the Matrox OpenDML group in February 1996. These files are supported by Microsoft, and are unofficially called "AVI 2.0". Files of this type have a .avi file extension name.
AVI files can be found online as movies, music videos, TV shows, streaming video and can even be downloaded as a full length motion picture.

MP4 is different with MPEG-4, MPEG-4 (ISO 14496) is a broad Open Standard developed by the Moving Picture Experts Group (MPEG), a working group of the International Organization for Standardization (ISO) which also did the well known MPEG-1 (MP3, VCD) and MPEG-2 (DVD, SVCD) Standards, standardizing all sorts of audio/video compression formats and much more. By its nature the MPEG-4 Standard doesn't aim at standardizing one potential product (such as: something comparable to DVD) but covers a broad range of Sub-Standards, which Product Providers can choose from to follow, according to what they need for their product.
The MPEG-4 Standard, as mentioned, is divided into many different sub-standards, where for our users on rzvideoconverter.com the following sub-standards might be of major interest:

• ISO 14496-2 (Video Video), for example: Advanced Simple Profile (ASP), as followed by XviD, DivX5, etc.
• ISO 14496-10 (Video Codec), Advanced Video Coding (AVC), also known as H.264
• ISO 14496-14 (Multimedia Container), MP4 container format (uses the .mp4 extension).

As an Video Video(Encoder/Decoder), it is a technology used to compress and decompress video data. Codecs can be found in software, hardware, or both. Codecs are used to make files that are usually large into much smaller sizes, making the file convenient to use in mobile device, portable device, etc., or transfer throughout the Internet, LAN, wireless devices, or any other file transfer methods.
As a Multimedia Container format, you can combine different multimedia streams(most of the time audio and video) into one single file, use the standard .mp4 file extension name.

MPEG-4 offer the advanced compression algorithm, esp AVC/H.264 Codec, and making the mp4 files convenient to use in mobile device, portable device, like iPod, iPhone, PSP, etc.
RZ Video Converter is the best avi to mp4 converter, support AVC/H.264 MPEG-4 Codec, can convert any avi files to mp4 files with the high quality.

For example:
I have two avi movies "[Heros][XVID].avi" and "Starcraft2[divx5].avi", i want to play these movies with my iPod, i know the best video format for iPod is MP4(AVC/H.264 video encode, AAC audio encode) format, how can i do to get the best mp4 movies for my iPod?
The best answer is RZ Video Converter, it can fast and easy convert avi to mp4 with high quality.

Step - 1: Run RZ Video Converter

Step - 2: Click "Add button" to add all source avi movies "[Heros][XVID].avi" and "Starcraft2[divx5].avi" into RZ Video Converter, or directly drag and drop all movies into RZ Video Converter. You can click "Play button or " to view the source movie.

Please Note:
1. Click "Play button" on "Source Movie
", you can view the source video.

2. Click "Play button" on "Target Proflie
", you will preview the target video with this target profile.

Step - 3: Check "SINGLE" and select a target profile, such as "iPod H.264 Movie(High Quality)(.mp4) Default for iPod "

You can click "Output Option button" to custom the target mp4 movie, include: video resolution, video bitrate, video framerate, video resize mode(Stretch or Keep ratio), aspect ratio, audio encoder, audio bitrate, audio sample rate, audio channels, etc.

Step - 4: Here you should select a hard drive folder, and click "Start button".


Once the conversion completed, you can get the high quality iPod mp4 movies from your avi movies.


Tips:
Please note, most mobile phones use 3GP file format, a simplified version of MPEG-4 Part 12, with the .3gp and .3g2 extensions. These files also store non-MPEG-4 codec data (H.263, AMR, TX3G), RZ Vide Converter can convert any videos to 3GP too.