Apple TV won't handle surround sound

Don't expect to get true surround sound from Apple TV.

(Credit: Aperion Audio)

With HDMI and optical digital output, Apple TV should eventually be able to pass DVD-like surround sound just as soon as Apple adds surround-encoded movies and TV shows to its iTunes Store--right?

Wrong.

According to the specs on Apple's Web site, the Apple TV's maximum audio track bandwidth for video files is 160Kbps (that doubles to 320Kbps for audio-only files such as MP3s and AACs). That is far below the 640Kbps and 768Kbps surround Dolby and DTS soundtracks you'll find on any old DVD. And that doesn't even begin to account for the next-gen Dolby Digital Plus and DTS-HD soundtracks available on HD DVD and Blu-ray discs, which start at 3,000Kbps and may eventually go as much as six times higher.

Basically, more bandwidth means there's more space in a file for the actual bits that make up a soundtrack--the more space, the better quality and more channels (six or more surround versus just two for stereo) are available. And because 160Kbps is a pretty tight fit for anything beyond very compressed MP3-like sound, it's a safe bet you won't be seeing surround-encoded files on the Apple Store--and thus the Apple TV--anytime soon. And because this appears to be a hardware limitation, it's probably not something that could be changed with a firmware update.

Yes, you can still connect an A/V receiver or home theater system and get a sorta/kinda surround effect from your Apple TV--just choose the Dolby Digital Pro-Logic II or DTS Neo:6 decoding option that's available on nearly all recent home audio systems. That will deliver a decent faux surround effect from the Apple TV--or any stereo source--but it won't be nearly as rich or detailed as the true multichannel bitstreams found on DVDs or HD discs.

For all the hype about digital delivery replacing optical disc media (DVDs, HD DVDs, Blu-rays), it's worth remembering that even the lowliest DVD holds up to 4.7GB of data. Even with improved compression, you'll need some serious broadband bandwidth to begin to offer a DVD-equivalent video and audio experience (true 480p and true surround sound)--and that's not even high-def. That's why I'm happily sticking with my DVD player and Netflix account for the foreseeable future.

[CanadianAvenger]

Is it a hardware limitation?

I'm not so sure... remember the Apple TV is a combination of hardware and software, so it may just be a limitation of the software codecs currently employed in the Apple TV. The specs are showing what it can do today, and that is limited by what the file format can currently support. It may very well be that the hardware can go much further (this would not surprise me) Surround support might be sold as an update through iTunes, much like the 802.11n update now available for the newer Mac's.

I think one key place to watch will be the AppleTV hackers who are now running DivX/XviD and see if they are able to spit out a proper AC3 stream.

[brianvh]

AC3 Format

Don't forget that surround sound wouldn't be processed by the Apple TV itself,
but passed through the TOSlink output to the receiver. Whether it has the
horsepower to mix down a 5.1 AC3 soundtrack for stereo output is another
question, but it could just decode the left and right front channels and ignore
the rest. Surround sound does seem to be a glaring omission, but they did
include that TOSlink connector, which isn't much good for anything else.
Don't be so quick to make declarations about what the machine can and can't do
based on posted specs.

[danieleran]

Not really correct or useful

iTunes movies bought from Apple have a Pro Logic soundtrack with surround
sound that is also compatible with standard stereo equipment. It is not fake
surround synthesized from stereo.

However, your article seems to conflate the technology used on 4-8 GB DVDs
with what can be downloaded over the Internet. DVDs use MPEG-2 video
compression and AC3 surround audio. Neither is appropriate for use in
downloads, which is why Apple uses the more modern MPEG-4 and AAC.

Apple's HD trailers use 5.1 AAC sound, which is better sound quality at lower
bitrates than the older AC3 format.

Your article might just as well complain that MP3 players like the iPod don't
play uncompressed CDs, and jump to the conclusion that the iPod must
sound awful because it's not using the huge bandwidth of CDs, when in fact
users won't hear the difference. Bandwidth isn't the same as quality.

Compare the article "Ten Myths of the Apple TV: 5.1 Audio"
http://www.roughlydrafted.com/RD/RDM.Tech.Q1.07/147048D8-
D8B7-45E7-9A97-3CD5B4C2B75A.html