MP3...in Surround Sound

A number of people sent in the latest news from the fine folks at Frauhofer that they are expecting to have surround sound working for MP3s by July. The details are pretty sketchy in the article, but supposedly it won't be much more space per MP3s, and existing players will work with it.

conversion

[tomocoo]

You couldn't convert your mp3's to surround because the source is stereo... if you want surround just run it through PL2 for pretty good on the spot surround sound.

Nothing to see here.

[sokk]

Ogg Vorbis have had support [ogghelp.com] for this for some while.

What I'm not sure of is if the support for "joint" surround is there. (Like joint stereo, only for surround)

Who wants to use a proprietary sound format, when they can use a much more appealing open format.

I thought...

[Bluesman]

...surround sound was encoded on the two stereo channels. At least I thought that was how it worked up until Dolby Pro-Logic wasn't the latest thing anymore and you had digital connections from the source to the AC-3 or Dolby Digital receiver or whatever. (I haven't kept up...)

I just assumed that the surround channels were basically a diff between the right and left channel and the center was a sum.

Vorbis can already do this :P

[Anonymous Coward]

Vorbis is also intended for lower and higher sample rates (from 8kHz telephony to 192kHz digital masters) and a range of channel representations (monaural, polyphonic, stereo, quadraphonic, 5.1, ambisonic, or up to 255 discrete channels)

http://xiph.org/ogg/vorbis/doc/vorbis-spec-intro.h tml [xiph.org]

Surround?

[Lord of Ironhand]

Isn't Surround Sound the technique of encoding 4 channels of audio (left, right, front, rear ("surround")) in 2 discrete channels, such as used by a lot of movies on TV? Since only 2 real channels are used, this was already possible using MP3.

Maybe "multichannel" would be a more appropriate description.

Re:Bait and switch?

[REBloomfield]

MP3 is already proprietary.

Re:Bait and switch?

[spacefight]

MP3 is and was always proprietary...

Re:How hard will it be to convert?

[Fulkkari]

Your original mp3s are in stereo and not in surround, so you wont win anything by converting them to the new format as far as I understand it. They would still be stereo (converting from mono to stereo doesn't either make the sound stereo). This new format would just mean that you could make mp3s with surround sound in the future.

Tell me if I'm wrong.

Re:MS ahead of the game??

[Zapdos]

Ogg has had it longer.

Re:Surround?

[Drakonite]

Isn't Surround Sound the technique of encoding 4 channels of audio (left, right, front, rear ("surround")) in 2 discrete channels, such as used by a lot of movies on TV? Since only 2 real channels are used, this was already possible using MP3.

Maybe "multichannel" would be a more appropriate description.

Surround sound is the technique of placing speakers around you so sound comes from all directions.

While it is true that some encoding schemes (i.e. Dolby) work by combining the various channels into just 2 channels, it does not have to be encoded like this to be Surround Sound.

Some Additional Tech

[Effugas]

Here's the deal.

By far, the most popular algorithm in use for surround sound encoding is Dolby's AC3 (I can say this, because it's on pretty much every DVD, and nothing comes close to its penetration even in the audio space -- not even DVD-Audio). AC3 itself is a pretty fascinating codec; one of the more interesting things about it is that each additional channel requires less and less bandwidth to tack on. This is because there tends to be massive correlation between channels -- either the same sound is coming from multiple directions, or a sound is coming from one direction and all the others are silent, or some combination therein. AC3 encodes this quite efficiently, and thus gets really high quality surround sound in surprisingly few bits.

I suspect they're engineering a similar mode for MP3 -- hopefully something a little nicer than Joint Stereo, which basically works by doing a mono mix and specifying which frequencies are louder in which channel. No, this doesn't work very well. Concievably, we could see something like VBR on a per-channel basis, but I suspect this would cause existing decoders to collapse. I do believe it's possible to place extra data between MP3 granules; I suppose they'll get their backwards compatible surround mode worked into there.

--Dan

Re:Competition

[ahillen]

Not very surprising. Considering that both AAC and Ogg Vorbis (and possibly flac, but I can not find the page) support 5.1.(search for 'surround')

Yes and no. AAC is not really competition from the point of view of the Fraunhofer Institute, since it's developed mainly by the same group [fraunhofer.de]:

"Fraunhofer IIS has been the main developer of the most advanced audio coding schemes, like MPEG Layer-3 (MP3) and MPEG AAC (Advanced Audio Coding)."

Re:Can someone enlighten me?

[David_Bloom]

Dolby Surround (the type found on VHS tapes) works similarly. It just contains data on what frequencies to spread out to what speakers or something. It's not true surround sound.

SPEELING !

[Anonymous Coward]

They are still called Frau n hofer Society.

Re:Some Additional Tech

[mudrat]

I suspect they're engineering a similar mode for MP3 -- hopefully something a little nicer than Joint Stereo, which basically works by doing a mono mix and specifying which frequencies are louder in which channel. No, this doesn't work very well. Concievably, we could see something like VBR on a per-channel basis, but I suspect this would cause existing decoders to collapse. I do believe it's possible to place extra data between MP3 granules; I suppose they'll get their backwards compatible surround mode worked into there.

That is precisely how MP3 mid side stereo mode works. It takes the sum of the channels (the common sounds) and encodes with a higher bitrate than the sounds that differ. Joint stereo is a mode where the encoder decides whether to use Mid-Side or true stereo for each frame depending on the stereo seperation. Joint stereo gives better results than true stereo at the same bitrate.

The mode you describe (mono with frequency info) is Intensity Stereo which few encoders even support.

Re:WOW. Awesome.

[cybin]

Yep -- there is SACD, which is kind of like DVD audio with the 5.1 encoding, but if you put a hybrid SACD disc in a regular CD player, you get the front stereo pair. It's been around for a while but isn't incredibly hot right now. Sometimes you can find SACD discs at Best Buy and such.

Re:I thought...

[daBass]

The system you mention is "Dolby Stereo". But "sum" and "diff" aren't the correct terms. Any signal that is in 100% phase on both left and right will end up in the center channel. Signals that are out of phase end up in the rear.

Now "Dolby Stereo" sounds like it is, well, stereo. So the marketing department decided at some point that it should be called "Dolby Surround", which is fair enough. "Pro Logic" is "Dolby Surround" for use in home A/V amps, but with "Pro" electronics (logic). Another marketing term for the same thing.

That system should work fine on any MP3. Stereo MPEG audio on DVDs (so not the Dolby Digital or DTS tracks) quite often have Dolby Stereo/Surround encoding on them as well.

The truth is that the BBC article doesn't have enough information and I think "Surround" is used as a general term to indicate more than two channels of audio. So no way of knowing what they actualy mean.

Re:Previous extensions, like mp3-pro, not successf

[AntiOrganic]

But it doesn't have six channels, it's the same old crap.

From the article, again:

Fraunhofer reproduces surround sound by adding to MP3 encoding extra information that describes the spatial characteristics of the main audio track.

Using this extra information helps MP3 players recreate the surround sound effect.

There's no extra channels, just an extra layer telling the player how to manipulate the two existing audio channels to obtain a surround-like effect. While the merits of this approach alone make me skeptical, what really bothers me about this is how different players are all going to have completely different implementations of using this extra layer of data to manipulate the audio channels, meaning we're going to have no consistency whatsoever with how it even sounds.

Surround

[robnauta]

Maybe there is confusion about the naming and what the article means exactly.
Surround sound is the technique to make stereo come from different directions. Either using virtual surround by splitting by frequency range or using additional information, like Dolby Surround with its phase encoding.
DTS and dolby digital 5.1 shouldn't be called surround, they are multichannel sound.
Ogg and WMA 9 both support multichannel sound. Of course all stereo formats support surround (dolby) as long as the phase information hasn't been lost (some modes of joint stereo do this).

Re:New format? Why?

[Bobman1235]

I don't know why you'd need to change anything... I get surround sound right now with my ordinary stereo MP3s. It's called Dolby Pro Logic :-)

Exactly right. Dolby Pro Logic works with regular stereo channels. If left and right are identical, it's the center channel. If they're exactly opposite (can't think of the "waveform" word for this) the sound goes to the rear channel. Otherwise they go to the front per usual. Other than making sure the sound is encoded in this way (which would take no extra "space", it's still just two stereo channels) I don't see what else they would have to do. If you want full discrete signalled digital surround sound, don't use the mp3 codec.

Re:Binaural Explained

[Anonymous Coward]

"A portable device could either use 4 channel headphones (expensive, requires 4 amplifiers to drive them, would increase battery consumption) or could use a DSP integrated circuit to decode the surround sound channels, perform the phase analysis done by the human brain, and send this synthetic binaural signal to regular headphones."

Sennheiser makes these. I have a DSP Pro [audioasylum.com]. It's pretty cool, you pick from some presets that help model the accoustics of your head to simulate stereo imaging, you can add things like echo, accoustic modeling for various room types and it does Dolby ProLogic decoding. It works well and sounds good and you can get them for pretty cheap. I got mine free when I bought HD580s. They've got a pocket-sized one called the DSP 360, but I don't have any experience with that.

Missing the point

[Egekrusher2K]

I think most people will miss the point entirely on this matter. MP3's of bands and music recordings, etc., will have absolutely no use for this tech. Where people will see the benefit is when ripping DVD's and encoding AVI files. The best, and smallest, format for AVI audio is MP3. This will enable people to encode MP3s at, say, 160kbps, and also have surround sound. I find this to be quite exciting. I know, I'm a dork.

Re:Nothing to see here.

[WWWWolf]

Other games that use Ogg Vorbis:

• Operation Flashpoint. (Quite a surprise to open up the game music datafile and get back a bunch of .ogg files, or read the modding guides and see them referring to Oggdrop... Regrettably, the game was released wayyyy before Vorbis 1.0, but the audio quality in the music and sound files is still more than decent. And the GOTY budget release also has red book audio tracks...)
• Serious Sam 2 (I've heard; not seen this personally).

Re:New format? Why?

[Piquan]

But if the encoder throws out phase information, then surround gets thrown out too. I could see this happening in a FFT-based codec.

FM radio is the same way, it wasn't always stereo.

Yes, but to rebroadcast a stereo FM signal, you have to be stereo-aware. The idea behind Dolby PL is that copying equipment didn't need to be PL-aware. But back then, all the duplicating equipment would preserve phase. These days, it may get chunked, inverted, or have other icky stuff happen.