Digital Audio Formats for Car Audio

Winding Down the Great Format Wars

As the music industry reels from its greatest upheaval in a century, it’s natural to expect some sympathetic shock in car audio, which obviously depends on the music business for source material.

Car audio technology tends to mimic the curve of the music industry (minus the sunken careers of label executives) and has in some cases helped legitimize new formats — 8-track cassette, cassette tape, DAT — and drive them mainstream.

Accepting the Inevitable?
And now before our eyes, we’re seeing the car audio industry react, and drive, the shift to digital compressed audio. To some this marks the erosion of sound quality and critical listening. To others, it’s simply a new and more convenient way to get music in the car.

Just a few years ago, the music business looked doomed. Compact discs were priced at $18-$19, and usually contained one or two radio hits among the rest of the record’s water weight filler. The major retailers like Tower Records, Virgin Megastore, Wherehouse and HMV disappeared one after another. And people were finding their music online, free or otherwise.

Now with the pendulum shifting back to center, and the viability of iTunes, Amazon and other digital media outlets, the industry’s future is emerging back into focus. And one thing is clear: the compact disc, a format that brought the business of its mid-80’s sales malaise and delivered it enormous profit, isn't likely to survive the end game.

It’s too early to bury CD entirely, though. They still fill racks in Best Buy and Wal-Mart. Artists and labels have done a better job packaging the aluminum-polycarb discs with eco-friendly jewel cases, gatefolds, and heftier liner notes. And some of the reissue packages — Miles Davis, John Coltrane, Rolling Stones — are making the case for CD (and DVD) as an archival medium, complete with books, photos and bonus material. But it still seems like arranging deck chairs on the Titanic. Cashing in before flaming out. The march to digital downloads is thundering, despite the absence of any physical media to show for it.

Rising Sales of Digital Files
Research group NPD found that in the first quarter of 2010, downloads comprised 40% of all music sales, a five percent increase from 2009, and double what they were selling three years ago. CDs still hold an edge, but it’s a precarious grip. If the current pace holds, even through swaying economic recovery, downloads will match CD sales in two years. With shrinking retail outlets, limited selection, a rise of music DVD sales, and the music industry’s preoccupied panic over downloads, the CD appears on a fated course to join cassette, MiniDisc, DAT and 8-track in the formats of yesteryear.

For many car audiophiles, this is probably unwelcome news. The CD has been the de facto format for determining sound quality for years. Reference material, test tones and SQ judging have depended on the digital authority of the compact disc. This has helped the CD hang on in car audio circles, where many scoff at the low bitrates of retail digital downloads and the perceived inferiority of files shrunk to one-fifth of their CD-quality size.

Hearing the Difference
That debate is one of the most heated in car audio right now. Hardcore audiophiles swear they can “hear” missing information, the bits that are deleted when compressing files into a lossy format like MP3, AAC or WMV. Others call nonsense on this argument, noting that the digital information deleted during compression is typically outside the range of human hearing, or is simply “dead space” in the original (CD-quality) source file anyway.

I got wrapped up in the argument when I first started dabbling in portable media. Like many, I fixated on bitrate, convinced that CD-quality was the only way I wanted to hear music. I bought a high-capacity (for the time) 20GB third-gen iPod and connected it to my Alpine deck, first via interface cable and box, and later through one simple cable in the glove box.

I didn’t really care about stuffing the iPod with thousands of MP3 files. I wasn’t in it for the hoarding. I figured it would hold about 25-30 conventional 80-minute “albums” as CD-quality, uncompressed WAV files. The big, heavy files did play some havoc on my search/seek functions on the iPod, as the portable’s cache wasn’t designed to access such large files. Those bloated files also compromised battery life when the iPod wasn’t plugged into power.

Recently, I finally caved. I’ve started encoding everything at 320 kbps. Songs and albums I download from iTunes arrive at 256 kbps. I’d love to posture and claim I can hear the difference between these lossy, compressed files and CD-quality. But I can’t. And I like to think I’m listening critically. I’m a musician, and value low, defined bass, and sharp kick drums. My car setup is not super high-end, but with an Alpine deck feeding Morel components, it’s a pretty accurate reference.

I’ve A/B’d CD-quality files, at their 1,411 kbps bitrate, and 320 kbps compressed files, and am hard-pressed to articulate any noticeable differences. I even want to claim I’m missing those sub-bass frequencies, the information I’m not supposed to hear, but rather feel. But it’s sounds and feels like it’s all there. The CD isn’t dead, but it’s definitely fighting a battle for relevance.

What's the FLAC, Jack?
Some hardcore car audio guys are still searching for that happy medium of lossless compression and superior fidelity. Some have pinned their hopes on FLAC, the Free Lossless Audio Codec. FLAC is big on the Internet among audiophiles, as it offers smaller-than-CD quality file sizes with seemingly no fidelity loss. One poster in a forum went so far as to try and stir up a campaign, encouraging readers to pressure car audio manufacturers into making head units that could decode FLAC files. It's a nice, pure sentiment. But one the major manufacturers are unlikely to heed. As other posters noted, FLAC is a niche codec, used largely by Internet music heads, and requires third-party software to decode and convert into something your iTunes or digital media player can recognize. True, there are bands out there like Pearl Jam and Radiohead that have offered live bootlegs and other bonus material as FLAC; it’s not necessarily a backwater format. But an incremental percentage of users likely won’t make the major manufacturers push it into development.

After reading through much of the debate online, in forums, in interviews, I’ve found a few generally accepted truths among audiophiles and casual car audio enthusiasts. First, most everyone prefers the convenience of compressed audio files. Most everyone has an iPod, Zune, smartphone, or thumb drive they use to play compressed files in the car.

How much you “hear” of what you’re missing (think about that for a second) will depend on how good your reference system is. A system comprised of expensive, very high-end components and DAC converters will likely spotlight the flaws in compressed audio, especially when the music is driven to the limits of the system’s power. Whether you can actually hear these differences, or just tell yourself you can, is a whole different study in psychoacoustics (interesting study here if you want to see one enthusiast’s home science experiment in psychoacoustics.

For most of us, riding around with good to very good systems, a high bitrate (256 or 320) MP3 file, converted with a good encoder, should deliver what you’d expect of a PCM (pulse code modulation) file from a compact disc. Jazz or classical tracks will likely most highlight the deficiencies in compressed audio, but your AC/DC and Slipknot should still sound pretty true.

Future Format
Where does it go from here? Well, the round aluminum disc may not be done yet. Many of us still like a physical object to contain our music (round objects have proven pretty popular as a format shape for decades). DVD-Audio didn't establish the foothold some had hoped, and some consumers saw it simply as a money-grab by labels eager to popularize a new format. But as Blu-Ray works its way into homes and gaming systems, its high-resolution ability and storage capacity could help it become the new standard. A format that offers both audio and video for home, and a massive amount of audio in the car, could be a winner.

And with bandwidth and storage getting cheaper, it may not be long before Blu-Ray files are as easy and quick to download as a 128kbps MP3 file. I’m convinced the sound quality vs. convenience debates we’re having today will be a moot point by 2015. And it’s a good thing too, as it'll take me until then to save for the entire Stones archive in Blu-Ray 7.1 surround.



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Popular Format Round-up

Confused by all the acronyms and techie-talk? Here’s a quick guide to the most popular audio file formats in use today.

-MP3: for better or worse, the current standard. A lossy format supported by almost all car audio hardware on the market. Some hate it, some love it, most of us accept it. It’s not the only answer. Stick to higher bitrates, like 256 or 320. The difference you hear between say 256 or 320 vs. CD-quality 1,411 is negligible, in my opinion, if perceived at all. The difference between a 128 or 192 kbps MP3 file and even a 256 file is, however, pretty noticeable.

-AAC: proprietary lossy Apple format. This is what you’re getting when you download from the iTunes store. Developed by the same German institute that patented MP3 in the early 90s. AAC uses variable bit rate encoding, which basically means the computer makes real-time encoding decisions in an attempt to preserve as much quality as possible.

-WAV: uncompressed, lossless file. CD-quality. Big file sizes, roughly 10MB per minute of audio.

-OGG Vorbis: interesting format, open-source, and a favorite of Internet guys that run their computers on Linux. Offers variable bitrate encoding. Not surprisingly, not supported by Windows Media or iTunes, or most portables on the market. Fans of the format point to its efficiency, saying it achieves high MP3 quality at a fraction of the bitrate and size.

-WMA: Windows Media Audio, Microsoft’s answer to MP3. Lossy format increasingly being marginalized. Was good for record labels and movie studios for a period when both were hellbent on Digital Rights Management, and WMA supported DRM. DRM has been largely been discredited these days as a clunky file protection scheme that angered consumers who only wanted to make a copy for the car, and found their hard drives scrambled instead.

-FLAC: loved dearly among audiophiles and online music traders (e.g. those swapping Dead and Phish bootlegs), praised for its sound quality and closest thing to CD without actually being CD. File sizes can still be pretty large, negating any gains from going with straight WAV files. Not supported by iTunes or nearly any portables on the market, necessitating conversion into another format. As an archival technology though—those saving their home CD collections to the computer—FLAC has a lot of fans.

-MP4/M4A: a container format good for compressing audio and video, and streaming both. Apple began popularizing the m4a extension to distinguish between an audio-only file. Files with MP4 extension generally contain both audio and video.