eclecticism

June 8th, 2004 |

I was just reading this Macworld article on how AirTunes works (the new audio streaming technology built into Airport Express), when I noticed this paragraph…

If iTunes is playing back a digital multichannel file format like AC3 (Dolby Digital) or DTS, those bitstreams are wrapped in Apple’s compression and encryption, and then decoded at the other end. In those cases, AirPort Express would end up streaming the raw AC3 or DTS stream via an optical cable to your home theater receiver for decoding.

blink

iTunes can play and output AC3 and DTS? How does that work — and from what source? Are there standalone AC3/DTS audio tracks out there somewhere? I’ve generally only seen them used on DVDs, though I know that there are some audio CDs made that use DTS, and probably some that use AC3. If I had such a CD, how would I put an AC3/DTS audio track into iTunes?

I don’t have a use for this information right now, I’m just really curious. It’s news to me.

iTunes: “Sweet Surrender (Roni Size v2)” by McLachlan, Sarah from the album Plastic Compilation Vol. II (1998, 4:00).

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5 Responses to “iTunes supports AC3 and DTS?”

Daniel Woods Says:
June 8th, 2004 at 2:23 pm

Super Audio CD (SACD) and DVD Audio (DVD-a) are rising in popularity, but can only be taken advantage of on newer CD/DVD Players. Since most CD Players out there are still Legacy Stereo Units, Music Publishers don’t release many SACDs or DVD-a’s.

Also, since you mainly listen to local non-Mainstream music, and the Mixing equipment for 5.1Ch Audio are not accessible to these (for want of a better word) “Indie” Artists, they are generally not released as SACDs. For an Idea on which genre’s of music are released on SACD, do a search for them on Amazon.

There doesn’t appear to be much documentation on the Internet, or in the iTunes Help files about SACDs, but (IIRC) the AAC format does support DTS and Quicktime can handle multiple Channel sound, so the logic suggests that SACDs can be used with iTunes

Jason Snell Says:
June 11th, 2004 at 9:34 am

Greg Joswiak insisted it did, but I can’t get it to work either. Perhaps he let slip a feature from a future update to iTunes?

Guy Says:
June 30th, 2004 at 9:51 pm

Hello there.

Just came across your page by accident while looking for something else. This link to an Apple tech note should clear things up for you regarding iTunes and multichannel formats such as DTS:

http://docs.info.apple.com/article.html?artnum=93870

I was interested in this subject because I wanted to know the circumstances under which iTunes would output EXACTLY the same words (bit for bit) on the optical outputs of my G5 that it read from an audio CD without messing around with them in the CoreAudio layer.

I have an outboard DAC connected from the optical out of my Mac to my hi-fi and I wanted to ensure iTunes could preserve the fidelity of the bitstream from a CD. This article indicated that it could.

Best regards,

Guy

Jose Perez Says:
July 15th, 2005 at 3:40 pm

It seems that I’m not the only one with the same question. So, If iTunes supports AAC (or ACC, MP4, M4A or whatever you wanna call it), does it mean that iTunes coverted tracks (AAC in M4A files) support multichannel streaming?

I have a very nice CD that I strong recomend - “Friday Night in San Francisco” by Al DiMeola, John Maclauglin and Paco De Lucia - Windows Media Player (version 9 or 10) detects it as a HDCD (High Definition Compact Disc). If you convert this HDCD to Windows Media Audio files over 128 Kbps (160 Kbps would be proper) and your PC have a 5.1 Sound System, you will be surprised that WMA files are compressed with 5.1 channel too ;-).

I really like iTunes and the audio quality, but it doesn’t seem to support HDCD (or SACD) multichannel format. Could somebody confirm this? Is this true or false?

Greetings from Venezuela.

ben Says:
January 26th, 2006 at 3:25 pm

HDCD is not multichannel, it is Microsoft’s proprietary extended bit technology that allows higher-resolution (think greater dynamic contrast on a track from loud to soft), and high-end CD players (or digital-out enabled ones) coupled with an appropriate reciever (or WMP 9 or 10, as you’ve discovered) can read the extra bits and encorporate them into the stereo signal. it’s not 5.1, however, as SACD can be(but it not always). DVD-Audio is also usually 5.1 channel.

iTunes doesn’t support DVD-A, HDCD or SACD. It can’t read any of those. What it CAN read is DTS-encoded tracks, which it reads as gibberish, unless it’s sending a bit-perfect signal to a DTS decoding processor such as a hi-fi surround reciever, over an all-digital signal. It must be all-digital for the DTS decoder to recognize and interpret the signal. Otherwise it will sound just like it would over a regular system: static and popping and nothing else. Apple Lossless format would be necessary to make this happen. No post-processing, either.

If you look around, you’ll find there are quite a few 5.1 DTS CDs out there. They are a DTS version of what would normally be a DVD-A or SACD album, and they fit on a normal CD. Incidentally, any lossless technology should be sufficient, when paired with a pure-digital connection to a decoder, to pass a complete 5.1 DTS signal…from just about any media player…