File Formats

Extension	Type	Notes
3gp	Media	Text, compressed audio, and/or compressed video, specially designed for use with mobile phones. Explained a bit by RFC 3839.
aac	Audio	MPEG-2 compressed audio.
amr	Audio	Compressed mono audio for GSM networks.
gif	Image	Typically cartoonish or images with a limited number of colors. It used to be a much more popular format, but it is being phased out slowly. If you want your animated gif on your phone, you might need to convert it to pmd format first. Check out the links page for other sites that detail this process.
jad	App Desc	Java midlet descriptor. This gives information about the Java program, such as which category the program should go into, the midlet's name, and who made it. Most of the same information is already in the Manifest file in the java archive (the .jar file), so I just use that to generate a .jad file. Also, since Sprint is so gosh darn picky, having the uploader write its own .jad file tends to work better.
jar	Application	Java midlet program. This is the compiled Java program. Many fun games and other applications are made into Java midlets.
jpg, jpeg	Image	Compressed images that are usually photographs. Great format. Life is good.
m4a	Audio	The compressed audio layer from an mp4 file.
mid, midi	Music	These are tiny sound files. It is essentially "sheet music" that your phone translates into a song. Great for the small size. Most often, they are used as polyphonic ring tones. AnvilStudio is free and will let you edit midi files.
mmf	Audio	Another version of compressed music. Same suggestions go for this one as for the mp3 format.
mp3	Audio	Compressed music, and a very common format for music that you will find online. If you are sending this to your phone, most likely you will want to make it mono and some low bitrate to keep the size down. Lots of phones don't support mp3 files, but the non-Sprint phones seem to support them more than the Sprint phones. I might suggest only 30 second clips, and downgrade them to mono, 96k/s or similar.
mp4	Media	Compressed video that some of the newer phones support.
pmd	Media	These are animations, screen savers, or little movies. To create them, you need either KTPIC or auAM. A bit of information about KTPIC is on Craig Given's site. They are alternatively called CMX files (Quallcomm CMS [Compact Media Extensions]). You can get more information on the format and read a FAQ on this type of file. You can download CMX Studio from Faith West Inc. Also, there are other sites listed on the links page that tell you how to convert files into pmd format.
png	Image	Designed to replace gif because Unisys irritated programmers about a software patent. A good format to pick for your phone or web site. Better compression for cartoons and animations.
qcp	Audio	Highly compressed audio. You can compress any sound instead of having just specific instruments. The format is made by Qualcomm PureVoice (info) and you can convert wav files into qcp format with their converter. Just make sure you start with a 8 khz (8,000 hz), 16-bit, mono .wav file. Detailed instructions are on the SprintUsers forum. Seems to be supported by just Sprint phones.
wav	Audio	Uncompressed audio. This is the "standard" for ripping music (before it is compressed to mp3), and it is a common Windows file format. If you want to play this on your phone, make the sound smaples short, mono, and probably 8khz.
wbmp	Image	Wireless BMP files -- not the same as a Windows BMP file. A Windows BMP file can be converted into a wbmp file with WapTiger's bmp2wbmp utility, or you can use their online form. This is a black and white format only.
wma	Audio	An audio file that has been compressed into a Windows Media Player type of format. Much smaller than wav files.
cab	Data	Some phones let you send cab files as a way to transfer data.