Saturday, April 7, 2012

Mastered for Mom: The High-Resolution Audio Debate Hits Home

Rolling Stone reported that musician and studio-quality digital audio advocate Neil Young has applied for trademarks indicating he has a high-res audio streaming service in development. The inventor of a lossy compressed audio codec used his website to argue that high-res digital is a waste of bandwidth. So who gets caught in the middle of this high-fidelity debate? My mother.

Mom now has an iPod, a birthday gift from some of my siblings. And I have accepted the challenge that, by Mothers Day 2012, I will have transformed two shoeboxes of her cassette tapes into a collection of iPod-friendly digital song files. The project enables me to confront the high-res v. compressed audio debate head-on.

The tapes cut a swath through some of the easiest of Easy Listening: Michael Crawford, Vic Damone, Ferrante & Teicher, Kathy Lee Gifford. (When did KLG record and release enough material to have a 2-tape "Best of ..." collection?) Cynics or audiophiles would argue that some combination of my mother's untrained ear, her relatively low-fi playback path (iPod to JBL personal speaker) and a lack of subjective artistic merit in the material would justify a quick-and-dirty A2D transfer process. But we don't advocate quick-and-dirty at In Aurem.

Apparenly, neither does Neil Young. According to the press release, his Pono service will present "the studio quality sound that artists and producers heard when they created their original recordings." Mom's music deserves nothing less. Recording the digital archive copy of a tape is linear and real-time; recording at low bit rate saves you no time over recording at high bit rate. So why not record in high resolution? Your downstream tools in the audio clean-and-repair pipeline produce better results with more information to chew on.

Christopher "Monty" Montgomery (of Ogg Vorbis fame) would take exception to that. But all his time-worn perceptual and subjective arguments — 16-bit/48 KHz source resolution is "good enough" and compression effects are "inaudible" — can be dismissed by the fact that 24-bit/96KHz (or higher sampling rate) is the standard for digital recording. If we can accommodate the bandwidth and storage, we might as well play back the studio master that the talent approved.

Only, I don't have the bandwidth and storage in this case. I have an 8 GB iPod and a lot of material to store on it. Ulitmately, I need an iPod-compatible compressed format in which to export my 24/96 masters, striking the optimal balance of fidelity to the original and small footprint. The finalists are:
  1. 256KBit/sec constant-rate Apple AAC produced from iTunes.
  2. 256KBit/sec constant-rate MP3.
  3. Variable bit-rate MP3 targeting "standard" quality.
Using the methodology and test set from my "Mastered for iTunes" analysis, the variable-bit-rate MP3 was proven to be closest (or near-closest) to the 24/96 master than the other two formats in all cases, and produced a signifcantly (>20%) smaller file in all cases. Results below.

(Blue text represents best result per column.)

Fidelity is always important. Compression is sometimes necessary. My approach to Mom's music is: 1) record in 24/96; 2) process in 32-bit floating-point; and 3) export tracks to "-V 2" variable-bit-rate MP3 files. The results so far are proving it was the correct choice. See you on Mothers Day.

            Analog-to-Digital Restoration #27           

Artist: Frank Sinatra
Title: Point of No Return
Genre: Vocal
Year: 1951

As they used to sing on Sesame Street, "one of these things is not like the others." Standing apart from the Easy Listening titles in my mother's shoeboxes is this Sinatra collection of brooding ballads. I may keep a high-res copy for myself; a little something, you know, for the effort.

© 2012 Thomas G. Dennehy. All rights reserved.

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