You might have problem understanding audio video formats. All formats vary from size and quality.
Audio Formats
WAV This is a uncompressed format used for CD quality audio.
MP3 This is compressed format, it remove some frequency to optimize music files.
WMA This format is developed by Microsoft used for DRM (copy protection) facility.
AAC Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates.
FLAC FLAC ( Free Lossless Audio Codec) is a codec (compressor-decompressor or coder-decoder) which allows digital audio to be losslessly compressed such that file size is reduced without any information being lost.
OGG This is better audio format as compared to MP3. This format is ideal for audio streaming.
AMR This format is used in mobile devices for recording audio files.
AIFF This is developed by Apple. This is loss-less and uncompressed format.
RI/RM This is good for audio streaming on internet.
RAW This is uncompressed format used in testing devices.
Video Formats
FLV Flash Video is a container file format used to deliver video over the Internet using Adobe Flash Player. Flash Video content may also be embedded within SWF files.
MP4 MPEG-4 is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital video and digital audio streams. Very good for video streaming in iOS devices.
DIVX (AVI) DivX Codec became popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality.
MPEG The Moving Picture Experts Group (MPEG) is a working group of experts for audio and video compression and transmission.
WMV Windows Media Video (WMV) is a video compression format for several proprietary codecs developed by Microsoft.
MKV/M2TS It is used to compress HD video files. It support multi channel audio.
VOB VOB (Video Object) is the container format in DVD-Video media. VOB can contain digital video, digital audio, subtitles, DVD menus and navigation contents multiplexed together into a stream form. Files in VOB format may be encrypted.
RM/RMVB It is used for high compression video streaming.
MOV QuickTime File Format (QTFF) is a computer file format used natively by the QuickTime framework.
3GP 3GP (3GPP file format) is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones.
Comparison of container formats