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11. Audio Coding Algorithms Part 1: Where the Rubber Meets the Road. 6/15/12 by Dave Immer

After I sent last week’s email, I got a few comments from folks who pointed out that the newer AAC is a better sounding coding algorithm than MPEG Layer II. I agree, and would encourage you to use AAC whenever possible.

And don’t forget APT-X, in my opinion, the best sounding algorithm out there. It’s been around since the dawn of ISDN codecs but didn’t really catch on like MPEG because it is kind of bandwidth-hungry. Standard APT-X needs 192kbs to deliver 20-20k mono and 384kbs for stereo. Source-Connect offers it as a low-delay option, which makes sense as bit-rate is less an issue over IP.

But there exists a strong inertia among ISDN codec users in favor of MPEG Layer II due to the existing large installed base of older equipment for which MPL2 is the best choice and AAC is not an option.

For this reason L2 Mono128 persists as the standard ISDN voiceover setting, if for no other reason than it’s easier to simply leave the box set on the most common codec. And so there has emerged an unwritten rule among users that MP2 is the expected setting.

Let me know if you have questions or comments about coding algorithms. Thanks,

-Dave