Digital Drive

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There's no free lunch

Posted by Charles Hansen on June 3, 2017 at 11:16:06:
The fundamental premise of MQA is to reduce the file size of a high-res file. To date the very best *lossless* way to do this was developed by Michael Gerzon in the 1990s, and his predictive algorithms forms the basis for all lossless compression schemes (eg, FLAC, ALAC, Dolby True-HD, MLP, Shorten, et cetera). Of these FLAC is the most commonly used and is considered the best overall optimization of these. None of them have a distinct advantage in terms of the overall file size after compression.

MQA reduces the files size by using lossy techniques. Specifically the least significant bits in the audio band of a PCM file are replaced by a compressed version of the ultrasonic audio data, resulting in a trade-off between bandwidth and resolution (no free lunch).

When starting with a 24-bit container, this may make sense in some circumstances. For example an original 96/24 file can be "folded" into a 48/24 container. Undecoded playback is at 48/17, while decoded playback is "unfolded" as a 96/17 file. It is up to the customer to decide if this is a step forward or a step backward.

However Redbook CD is limited to 16-bit containers. My understanding is that a decoded MQA CD would yield 88/13 playback, and undecoded would yield 44/13 playback. Again, it is up to the customer to decide if this is a step forward or a step backward.

As always, my posts reflect my personal opinions and not necessarily those of my employer or friends.