If you like to play MPEG-4 encoded files, such as files with extensions .MP4 and M4A, then you may like to think installing '3ivx' package. 3ivx is an MPEG-4 toolkit that supports MPEG-4 Video, MPEG-4 Audio and the MP4 file format.
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Here is more information about 3ivx toolkit:
The 3ivx decoder plays back most MPEG-4 files (including MP4, M4A, 3GP and MOV files) with MPEG-4 AAC Audio and MPEG-4 Video (such as DivX 3, 4 and 5, Apple MPEG-4, Philips MPEG-4 and XviD) using Windows Media Player or other compatible players. The Audio Decoder can play back MPEG-4 Multi-Channel High Efficiency AAC including audio encoded by Nero AAC and iTunes.