M4A files are a type of audio file developed and popularised by Apple. Since 2007, music purchased through the iTunes store has been in m4a format, therefore accounting for over 15 billions files worldwide. MP4 and M4A files are often confused, and the two are quite similar, being both based on the MPEG-4 codec. However, M4A is a file comprising solely of audio, whereas MP4 may also contain video.
M4A files are superior to MP3 in terms of the scale of compression and audio quality. The M4A file uses Apple's codec and resides within the MPEG-4 container. The main benefit of M4A is that files are compressed but are lossless. This means they can be decoded back to the original quality they were at the point of compression. Another benefit of M4A files are that do not carry any Digital Rights Management (DRM) protection associated with other files meaning they are less restricted.
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The .ogg file format is a type of audio file that makes use of open source Ogg Vorbis compression. It is supported by devices such as Archos and Samsung but is not supported by Apple iOS devices. The .ogg format has been utilised for the provision of streaming audio. The file format is unlikely at present to take a dominant share of the digital music market due to the synonymous nature of MP3 with digital audio.
The .ogg format is actually a container that potentially allows for different streams of audio, video and metadata. Ogg Vorbis is the compression format. It provides medium to high quality audio at between 16 and 128 kbps/channel and is better quality sound than mp3. The OGG file type is a lossy codec which means that data is discarded as part of the compression technique, resulting in a smaller file size. Ogg files are optimised for music files, but will still be of acceptable quality for speech only files.
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