3GP is The Smallest Video Compression

The reason why a video has a small size is because it is compressed. Same like picture or audio. For picture we can change the resolution of the image and also the amount of the color and save it into compression format. Uncompress picture normally in raw format or tiff and the compression format is jpg or gif. For audio we can change the bit rate of the sound. Uncompress audio normally in wav format and the compression we usually know is mp3. How about video? Video combine this method. For compressing video we can compress the file size by compressing the visual and sound. Compressing the visual can be done by resizing the visual size and change the video frame rate. Compressing the audio can be done by changing the bit rate and if you want more less file size, you can cut the sound from stereo to mono.
Some compression video format normally has it combination to make the compression; all you have to do is customize them. Smaller video size effect the small file size.
When you asked me what is the smallest size video format? You can find the answer by using your logic thought. Where do you find the smallest video size and all people using it? On the phone!
The video format on your phone is 3GP. Based on Wiki 3GP is a simplified version of the MPEG-4 Part 14 (MP4) container format, designed to decrease storage and bandwidth requirements in order to accommodate mobile phones. It stores video streams as MPEG-4 Part 2 or H.263 or MPEG-4 Part 10 (AVC/H.264), and audio streams as AMR-NB, AMR-WB, AMR-WB+, AAC-LC or HE-AAC. A 3GP file is always big-endian, storing and transferring the most significant bytes first. It also contains descriptions of image sizes and bit rate. There are two different standards for this format:
3GPP (for GSM-based Phones, may have filename extension .3gp)
3GPP2 (for CDMA-based Phones, may have filename extension .3g2)
3 GP created to overcome the limitation of capability processing heavy duty task because phone is not like computer. It also created to overcome the appropriate video size for phone and the limitation of memory. With 3GP format people will able to use it to make a video call. Using 3GP format for video call will not need a great effort for your phone to do the process. I believe there are consequences if you want to get the small size of your video. The first one is the video quality and second is sound quality. But you cannot check this on your phone for detail video because the phone resolution is also limited. In my opinion if we view from phone, the video still looking good.
There are many small video like wmv, divx, ogg, asf, flv, mov and many more but for me the smallest video file you can find from 3GP.

Note: You can also find this article at helium.