Are MP4 audio files compressed, or are they a lossless format like FLAC?
Answer Chris, Compressed. MPEG4 is a file format that is commonly used to store media types defined by the ISO/IEC Moving Picture Experts Group, though it can store other media types as well. The files of this format usually have extension .mp4. The start point design of the *.mp4 file format was Apple’s QuickTime file format. Having been improved in many ways, today MPEG-4 differs markedly from its predecessor. MPEG-4 allows each streaming over the internet, multiplexing of multiple video and audio streams in one file, variable frame- and bit-rates, subtitles and still images. Being quite often used as the alternative to *.mp3 on an Apple iPod and in iTunes, *.mp4 is still not as widely used in computer and hardware players as the *.mp3 in spite of the higher quality of the AAC codec. The following kinds of data are recommended (for compatibility reasons) to be embedded in MPEG-4: Video: MPEG-4, MPEG-2 and MPEG-1 Audio: MPEG-4 AAC, MP3, MP2, MPEG-1 Part 3, MPEG-2 Part 3, CELP (speech)
