If you’ve downloaded AVI files and tried to play them in Quicktime, only to discover that they don’t play with any audio, then try installing A52Codec.  It provides a codec for AC3 audio in quicktime, with the following features:

  • Multi-channel decoding of AC3 audio (can do full 5.1 decoding).
  • Implemented as a core-audio component so it is available to both Quicktime and Core Audio components.
  • Includes an AC3 importer so QuickTime can read .ac3 files directly.
  • Includes a preferences file to enable or disable dobly surround encoding as well as dynamic range compression.

See the A52Codec website for more information.  Once you have downloaded the A52 Codec you should have no problems playing these files.

Perian

In addition to A52Codec, you could alternatively have a look at Perian – an open source project which provides AC3 support as well as a large number of other codecs:

  • AVI, FLV, and MKV file formats
  • MS-MPEG4 v1 & v2, DivX, 3ivX, H.264, FLV1, FSV1, VP6, H263I, VP3, HuffYUV, FFVHuff, MPEG1 & MPEG2 Video, Fraps, Windows Media Audio v1 & v2, Flash ADPCM, Xiph Vorbis (in Matroska), MPEG Layer II Audio
  • AVI support for: AAC, AC3 Audio, H.264, MPEG4, and VBR MP3
  • Subtitle support for SSA and SRT

They do call it the Swiss Army knife of Quicktime components!  Head over to www.perian.org to read more.

Thanks to Graham Booker (the author of A52Codec) for the updated information provided in this post.