M4A is a filename extension for AAC container format and is developed by Apple Inc. M4A music is bought on the iTunes Store and does not come with DRM protection. In terms of quality, M4A is better than MP3 because it is lossless but still compressed. This means that it occupies less storage space and doesn’t lose quality over time.
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MPEG-1 is a compression and encoding system defined by MPEG (Moving Pictures Experts Group). It creates multiple frame sequences of I, B, and P, with the I frame containing all picture data. The B and P frames only store information about the changes on the last I frame. Typically, MPEG-1 uses 1.2 Mbps data rate, which is the speed rate of CD-ROM.