Answerman
Why Do Discs Use Different Audio Formats?

by Justin Sevakis,

Edward asked:

I have recently started to care about the audio of the anime I buy, and wish to know why the English/Japanese audio differentiates from one another and why there is no consistency in animation publishers' audio descriptions. For example, A Certain Scientific Railgun Season 1 has 5.1 dolby surround sound for english and stereo audio for japanese, while season 2 only has stereo for both. My Gundam Unicorn movies have both 5.1 surround sound in english and japanese. Funimation uses Dolby TrueHD 5.1, but Sentai uses DTS-HD Master Audio for most blu-rays. Aniplex uses Dolby Digital 2.0 for my Fate/Zero Limited Edition blu-ray. The japanese is listed as Linear PCM Stereo. I'm very confused as to why all of the differences, and if I got my money's worth.

Audio is important, and many fans are becoming more and more concerned with making sure that they're getting the best quality audio possible when they fork over the money for a shiny disc of their favorite show. But with so many different formats, which one is best? Which ones should you be asking for? Sometimes the difference is negligible or non-existant, other times it makes a huge difference.

Let's start with the easy one: why some shows have 5.1 mixes for the dub, but not for the original Japanese. I've answered previously on this column that most TV anime doesn't bother with anything more than a stereo (2.0) mix because the Japanese broadcast standard doesn't really support 5.1 audio, and given how big home theater systems aren't as common in Japan for a number of reasons, they generally don't bother remixing for 5.1 when it comes time to release the discs on home video. However, when making the dub, an American publisher might think 5.1 is worth the extra work. If they're already set up to do 5.1, the audio has to be remixed anyway, so it is an opportunity to have a nice added feature for dub fans. Early in the DVD era, the bonus of 5.1 audio was thought to drive higher disc sales. (It didn't.)

5.1 mixes require special equipment, take a lot more time, and are harder to check for errors (and requires a lot more office space to do so), so it's often not practical to do 5.1 mixes for everything. They can also cost more money. The decision to make a 5.1 mix is made on a show-by-show basis, based on whether the Japanese is 5.1 (usually just movies and some high-end OAVs) and how much the show is predicted to sell.

As for what format in which they're stored on a disc, these days you generally see 4 different kinds of audio tracks:

  • Linear PCM (Completely uncompressed, basically just a WAV file. Takes up a lot of space, especially in 5.1.)
  • Dolby Digital (AC3) (Lower quality, like an MP3, but takes up a lot less space. Supported by DVD and Blu-ray.)
  • Dolby TrueHD (Blu-ray only. The full quality of the WAV file, but compressed to a more manageable size. Still much bigger than AC3, however.)
  • DTS Master Audio (Blu-ray only. For the end user, pretty much identical to Dolby TrueHD.)

When you make a DVD or Blu-ray, you are tasked with squeezing a lot of data onto a finite amount of space, so compression can be very important. Wasting too much bandwidth on audio means you might have to sacrifice video quality. The above compression formats are essential ways to get the most quality out of an audio track without having an unwieldy amount of data to contend with.

Audio quality obsessives swear that Dolby Digital AC3 audio has a lot of distortion and they can DEFINITELY tell a difference. I am skeptical. I've definitely heard bad AC3 encodes that definitely affected audio quality, particularly in very early DVDs, but there has never been a double-blind study that shows even audio experts can tell a difference at higher bitrates (and quite a few proving that nobody can tell at all). At any event, the presence of "lossless" audio (in either LPCM, DTS-MA or Dolby TrueHD) has become an important marketing bullet point for Blu-ray discs, so whether people can REALLY tell the difference or it's all a placebo effect, who am I to argue.

Honestly, while 5.1 audio tracks are nice, I don't think they're a make-or-break thing for most people. And while people complain endlessly about lossy AC3 audio making it onto Blu-ray, I don't make a big deal about it in my own living room. You can proceed to the comment section, where a small army of people will breathlessly post that I'm wrong about this, but people believe whatever they want.


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Justin Sevakis has worked in the anime business for nearly 20 years. He's the founder of Anime News Network, and owner of the video production company MediaOCD. You can follow him on Twitter at @worldofcrap.


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