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Low-bandwidth Net Radio

Posted by michael on from the bit-conservation dept.

An anonymous reader writes "Slate has an article about Internet radio stations that use the aacPlus codec from XM satellite radio instead of MP3. Some of the ones they link to sound pretty good even at 24 kbps."

19 of 143 comments (clear)

  1. What about other codecs... by RizwanK · · Score: 3, Interesting

    I was under the impression that the sat broadcasting folks used MP2, optimizing quality and losing some of the psychoacoustic flaws inherent in Layer 3. I last heard about this when I swung by Sirius Radio though, and this was 2001. Anyhow, I'm finally starting to get things coded in AAC, and now theres another subset?!

    1. Re:What about other codecs... by tomstdenis · · Score: 4, Insightful

      Um... psychoacoustic modelling IIRC isn't part of the standard. The standard mandates things like bit format and DCT precision.

      So if your MP3s sound like crap

      - up the bitrate to something reasonable
      - Get a good source to encode from
      - change the encoder [lame -q 0 is great]

      Tom

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    2. Re:What about other codecs... by kevinadi · · Score: 5, Interesting

      Blame MPEG for creating confusing standard :)

      Anyhow, the MPEG-2 AAC and MPEG-4 AAC are basically identical, except for the addition of some coding tools designed for low bitrate encoding, like internet radio.

      There are some profiles for AAC encoding, which are (in decreasing quality) Main, Low Complexity (which we see in FAAC and Apple's), Low Delay, and the newest is High Efficiency which is low bitrate. There's also a scalable profile thrown in for good measure. I presume AACplus is actually AAC-HE. The technology they're using is from MP3plus we've seen quite some time ago but never takes off. So rest assured that you're not missing anything if you got your collection coded in AAC-LC.

      Also, the previous poster is correct. The psychoacoustics are not defined in the standard. Hell, even the encoder is not actually defined. They only define the decoder and the stream format to ensure interoperability. But yes, obviously MDCT sizes are clearly defined otherwise you can't reverse transform the coefficients. But if you so choose you can ignore their specification on transient handling and your stream will decode correctly, although with crap quality.

  2. Just a random thought here, by QuantumG · · Score: 4, Funny
    but maybe the other stations are choppy because there's actually a large number of people listening to them at the same time.

    But hey, what do I know?

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    1. Re:Just a random thought here, by mattspammail · · Score: 3, Interesting

      Satellite radio is only one way communication. It sounds choppy on the voice channels, because they use a lower quality bitrate. The music channels have a higher bitrate. The number of listeners is not a factor, since it's one way.

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    2. Re:Just a random thought here, by ZorinLynx · · Score: 3, Informative

      Satellite radio is a broadcast medium, which means one signal is sent down to a large area, and anyone in that area can receive the same signal without quality loss as the number of listeners goes up.

      It can be compared to any other radio broadcast; just because you're listening to 99.9 RIAA-0wn5-j00 FM doesn't mean other people have a weaker signal or diminished sound quality.

      -Z

    3. Re:Just a random thought here, by simcop2387 · · Score: 3, Informative

      just because you're listening to 99.9 RIAA-0wn5-j00 FM doesn't mean other people have a weaker signal or diminished sound quality.

      they wont have a diminished sound quality (for the most part, if its all on the edge of the range they might). but they most definately will always have a weaker signal in the immediate area. this is because your antenna itself distorts the field around it when it attracts the singal, and a small amount of energy is used in the reproduction of the sound wave when the receiver is receiving the signal. now typically this is such a low drop that you wont notice it but it is there.

  3. Ogg streaming seems pretty good by Xenna · · Score: 4, Interesting

    I'm not an ogg-head but I was pleasantly surprised by the quality of 32 Kbit ogg streams a while ago.

    http://www.virginradio.co.uk/thestation/listen/ogg .html

  4. Avoiding the 'L' word.... by mAineAc · · Score: 3, Interesting
    If you're on a Mac or other non-Windows computer, install the free VLC player instead of Winamp.

    I like how they avoided using th 'L' word in their report.

    1. Re:Avoiding the 'L' word.... by Anonymous Coward · · Score: 3, Interesting

      BSD? Unix-based? Amiga? BeOS? SkyOS? ReactOS? Hurd? Atheos? Plan 9? VMS?

      Oh, that's right. Linux is the only acceptible non Windows/MacOS operating system.

  5. XM @ 40kbps per music channel, quality still OK by bishr · · Score: 3, Interesting

    I subscribed to XM for about three months, and one of the main reasons I canceled was that the quality was not quite what I wanted. It was pretty good, but some of the "harshness" that you get with lower-bitrate Vorbis, AAC, etc, with cymbals, was pretty jarring to me. I've reencoded files in OGG, WMA at 64kbs, and it's fairly equivalent (though, of course, this is IMHO and therefore totally subjective.) I haven't tried lower bitrates, but as I recall, Vorbis scales downward very well. This may or may not be the new champ for low bitrate sound quality, but this is NOT revolutionary.

    Speaking of XM, it seemd to be feast or famine- either they're playing stuff I like on several channels at once, or I flip around for an entire hourlong drive withouth finding anything - the other main reason why I canceled.

  6. The Interesting Bit is in the Last Paragraph by conJunk · · Score: 5, Insightful

    Reading the article, my first thought was "so what? So we can ultracompress audio so it sounds good at low bandwidth? What's the point?" Truth is, everyone (at least in the west and industrialized Asia) has or will get broadband, *especially* those who are interested in things like net radio.

    Then you get to this bit:

    It seems crazy until you try it, but Mostly Classical proves that aacPlus can sound great at 24 kpbs. At 48 kbps, it's almost as crisp as a CD. At 128 kbps, it can deliver 5.1 channel surround sound.

    Using the compression to deliver multichannel surround sound is pretty cool. In 5, 10 years, we'll probably have a really flash standard for home audio, and it's nice to know that some folks are thinking ahead to make sure we'll be able to get it streaming on our DSL lines.

  7. Low bit rates works well with speech. by MtViewGuy · · Score: 3, Interesting

    I think while these low bit rate transmissions might not be great for music, they do work pretty well for transmission of mostly speech broadcasts such as news, radio talk shows and sporting events.

    I think because we're so used to talking over landline telephones with its relatively poor sound quality, Windows Media and Real audio streams transmitted at 16 kilobits per second and the audio stream mentioned in the article sounds reasonably well for mostly-speech programming.

  8. It's good to see by Dorsai65 · · Score: 5, Insightful

    that folks are (again) distinguishing between the quality needed for casual use (having background noise) and sit-and-listen-to-it quality (CD/live).

    One of my peeves about broadcasting over the net is that so many people want perfect signal, regardless of what they're using the broadcast for. The added bandwidth needed for studio-quality everything just means ever fatter pipes are demanded, raising the cost/price of the whole infrastructure and adding to the net congestion.

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  9. i dont get it by hasst · · Score: 5, Interesting

    I really don't see the point in this article. I've read it, and then re-read it. They are comparing a "new" codec with MP3, Windows Media 8 and Real Media 8. The document in which they present the "clear winner" is dated June 2003. In my time that's more than a year and a half ago. Meanwhile we have OGG and even newer MS/Real codecs. I don't see them comparing with the ogg codec wich is considered now the open industry standard. I have made the migration for a really big radio station from Windows Media to ogg, BUT based on a demonstration of the clear qualities of this open codec. You can listen a 22khz, 16 bit, mono stream at 20kbps (more than dial-up friendly). You have CD quality at 64kbps VBR (insignifiant for any broadband connection). All this using ogg. You have support for it in most of the music players around. Why don't I see a relevant competitive analasys between this and aacPlus? Why should I care about it being better than codecs that are mostly irellevant at this moment?

  10. SomaFM by HoneyBunchesOfGoats · · Score: 5, Informative

    SomaFM, an entirely listener-supported Internet radio site, has a few streams in aacPlus. I recommend them, they play stuff that you normally don't run across.

  11. Here's how 24kbit/s MP3 sounds (Lessig audiobook) by turnstyle · · Score: 3, Interesting
    When I put the Lessig audiobook together, I finally settled on 24kbit/s MP3s (in true mono).

    Listen to Ch.1 by Doug Kaye and/or Ch.13 by George Sessum, as those files were properly recorded (some of the others were first-time recordings, and they didn't get their levels right).

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  12. aacPlus == HE-AAC by Skuto · · Score: 4, Informative

    aacPlus is just a marketing name for the HE-AAC standard.

    There are GPL'ed implementations of HE-AAC decoders, for example at http://www.audiocoding.com, so these streams should be playable on open source systems, too.

    Btw. Some of technical details in the article (notably about parametric stereo) are *complete bollocks*. What they describe is Mide-Side stereo.

    Parametric stereo transmits only a mono channel plus a very small amount of sideband information that describes how to reconstruct the stereo image (via decorrelation and fading).

  13. Re:platform irony by moonbender · · Score: 3, Insightful

    OK, so Winamp isn't installed by default, but is is becoming the player of choice for the IT cogniscenti in place of WMP.

    Hm. First off, I wouldn't say that Winamp is becoming anything - it already is, and has been for a while. People, and not only "IT cogniscenti" (aka geeks), have been using Winamp in the days when WMP wasn't a generally known acronym. To me, Winamp was the player of the period when MP3 was still new (remember oth.net and AudioGalaxy?). I kind of doubt the number of users is still increasing, in fact I imagine that if anything, the number is decreasing.
    I might be wrong, though - so, what is the choice among the geeks these days? Do you all still use Winamp? Personally, I've been using Foobar for a long time now, mostly because of it's small footprint, straightforward interface and out-of-the-box global hotkeys. Because I'm so happy with it, I really haven't even looked out for any other new players, so I'm curious as to whether I've missed anything. (And I don't mean iTunes for Windows.)

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