Audio and Video File Formats: An Introduction
FILE FORMAT
There are several commonly used audio file formats. There are fewer video file formats, but video and audio file extensions can be confusing. This is just a brief description of the most widely used audio and video file formats and systems.
AAFC:Advanced Audio Coding This is the audio file format used by Apple for the iTunes Music Store and may appear with the M4A file name extension. It is better than MP3 for sound quality. It was developed as part of the Dolby-owned MPEG4 group (see below).
IN: This audio file format is the standard used by Java, Sun, and Unix.
MPEG: Moving Picture Experts Group There are now several types of MPEG, which are described below.
MPEG-1: This is used in digital cameras and camcorders for small video clips. VHS quality playback of MPEG-1 can be expected.
MPEG-2: Used for digital satellite TV, professional movie recording, and home DVD recording. It provides provision for multi-channel surround sound recordings.
MPEG-3: MPEG-3 was proposed as an entity, but was eventually merged with MPEG-2.
MPEG-4: This is the newer MPEG system and is used to stream content from the Internet. It is also used in portable video recorders and for Internet downloads. Required for DivX. Enhances digital broadcasting and interactive graphics and multimedia.
MP3: Digital audio files, most used to store and play music. It compresses the files to about 10% of a normal audio file, and a normal music track will be about 5-6MB in size. MP3 stands for MPEG-1 Audio Layer 3, not MPEG-3 as many people think. A typical MP3 audio file is close to CD quality.
ogg– An audio file format that is supported by a variety of codecs, the most popular of which is the Vorbis audio codec. However, MP3 files are much more compatible than Vorbis.
arkansas: Real Audio This format is designed to transmit audio over the Internet. It is a self-contained file format with all audio information stored within the file itself.
WAV: The simplest audio file format, developed by Microsoft and IBM, and built into Windows 95. It is an uncompressed audio file format with large file sizes (10 x MP3) and requires no additional processing to play. The WAV file consists of three blocks of information: the RIFF block that identifies the file as a WAV file, the FORMAT block that identifies parameters such as sample rate, and the DATA block that contains the actual data or music sample.
WMA: Windows Media Audio A digital system invented by Microsoft and used in portable digital audio players. Using WMA, a file can be made uncopyable and can be used for copyright protection.
WMF: Windows Media Format These are audio and video files comprising of WMA and video codecs. They provide high quality and media security for streaming and downloading and playing applications on computers.
WMV: Windows Media Video Used in Windows Media Player, used to stream, download, and play audio and video content.
When it comes to audio and video file formats, you’ll sometimes notice the term ‘codec’. A codec is simply short for encoder-decoder (or compressor-decompressor). A primary function of a codec is to compress audio or video data streams to speed up the transmission of digital audio samples and video frames and reduce storage space.
The goal of all codecs is to minimize file size while maintaining audio and video quality. A quick indication of where the codec is in the transmit and receive path is:
Video device (for example, camcorder) – video capture card – digitized video – codec (compresses digital information) – output (MPEG2, AVI, WMV, etc.) – codec (decompression) – video frames – display device .
Between the two codecs, the compressed result is transferred to the display device, streamed, stored in a file, etc.). So to further condense the flow, we could basically describe it as:
raw data – codec – transmission – codec – playback
This is simplistic, but it shows where the codecs are used. Therefore, in order to play a movie, video or piece of music of a certain format, you need a codec on your computer that allows you to unzip the file and play it.
Here is some free software that checks what codec a video system uses and what codec your system needs to play it:
codec tool.
The different video file formats are required to meet the requirements of various video devices. Similarly, audio file formats are designed to meet the needs of specific delivery methods and storage and playback devices introduced by large corporations such as Microsoft, Sony, and Apple. Thus, Sony invented the UMD (Universal Media Disk) for the PSP (Playstation Portable), and Apple introduced AAC (M4A) for its iPod.