Master Quality Authenticated

Master Quality Authenticated (MQA) is an audio codec intended for high fidelity digital audio internet streaming.[1] Launched in 2014 by Meridian Audio, it is now being marketed by MQA Ltd.

History

Announcement of MQA was made on 4 December 2014, with 7digital being mentioned as partners. Availability in "early 2015" was promised.

Codec description

The basic premise is, akin to XRCD/HDCD/aptX in some ways, to hierarchically compress the relatively little energy in the higher frequency bands into compressed data streams, which are then embedded into the lower frequency bands using proprietary dithering techniques.

After a series of such manipulations, the downsampled 44 kHz/16bit data (dithered partially with the last-step data stream), the layered data streams, and a final "touchup" stream (compressed difference between the lossy signal from unpacking all layers and the original) are provided to the playback device. Given the low amount of energy expected in higher frequencies, and using only 1 extra frequency band layer (upper 44 kHz band of 96/24 packed into dither of 48/16) and one touchup stream (compressed difference between original 96/24 and 48/16) are together distributed as a 48/24 stream, of which 48/16 bit-decimated part can be played by normal 48/16 playback equipment.

One more difference to standard formats is the sampling process. The audio stream is sampled convolved with a triangle function, and interpolated later during playback. Theory of such sampling is explained in these slides: http://icms.org.uk/downloads/BtG/Dragotti.pdf

Compared to FLAC/ALAC and other lossless formats, there is no factual bandwidth saving, and the 48/16 signal has easily identifiable high-frequency noise in the 3 LSB bits. Based on information available, the fully decoded MQA signal is 352 kHz at 24 bits. Whether it's lossless or "only keeps timing information to remove ringing and echo" remains to be seen.

One of the features provided by MQA is the ability to play it as 48/16 PCM on legacy devices. Another feature is watermarking and DRM.

Based on latest information from Auralic, a manufacturer of Audiophile Wireless Audio Streamers, Meridian Audio prohibits digital output of unpacked MQA in any digital format, only allowing the unpacked data to be fed to an on-board MQA-compatible DAC and output in analog form. This is most probably a part of DRM initiative.

A comprehensive Q&A done by ComputerAudiophile with Bob Stuart has been posted here: http://www.computeraudiophile.com/content/694-comprehensive-q-mqa-s-bob-stuart/

Reception

Some early results from analysis of 2L-provided MQA files: http://www.computeraudiophile.com/blogs/miska/some-analysis-and-comparison-mqa-encoded-flac-vs-normal-optimized-hires-flac-674/

Marketing

For partners interested in playing back the format, Meridian is providing object code to run on multiple platforms, which is going to be integrated or provided as part of MQA-specific firmware. Current reference platform for testing is XMOS xCORE-200. The playback device requires payment of royalties to Meridian per unit sold, as previously with DVD-Audio's MLP.

References

  1. ↑ Radding, Ben. "Studio-Quality Music Streaming Coming Soon From MQA". PCMag. Ziff Davis. Retrieved 15 April 2016. MQA is a digital encoding and playback service, standing for Master Quality Authenticated, which aims to deliver master studio quality sound in a file that's small enough to stream or download
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