What bitrate does super audio/hd audio start at?

Discussion in 'Playback Devices' started by Ken Burkstrum, Dec 16, 2005.

  1. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    I fit it all in the title.
     
  2. Tim Hoover

    Tim Hoover Screenwriter

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    Hi-rez is usually understood to mean 24 bits at a minimum 48kHz sampling rate. Of course, there are some Dualdisc purveyors (Sony most notably) who will claim an "enhanced" stereo track that is merely 16/48.
     
  3. ChristopherDAC

    ChristopherDAC Producer

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    It depends if you are talking stereo or surround. DSD from SACD is one bit per sample, sampled at someting like 1.25 MHz if I recall, so a stereo SACD track would be about 2500 kbps after unpacking from DST form. 24 bit, 96-kHz PCM stereo would be 4608 kbps. This is excluding subcodes &c. 5 channels of 24-96 would run 11520 kbps, over the DVD transfer rate maximum, which is why it needs to be packed with MLP.
     
  4. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    You lost me with all the abbreviated terms.

    Can you tell me how you figure bitrate by looking at the bits per sample and hertz sample rate?

    DSD?
    DST?
    MLP?

    How much space do SACDs store, are they just DVDs?
    What's the difference between DVD-Audio and normal DVDs?

    I've never tried putting music on a dvd and playing it in a dvd player like I would a CD, does that work?
     
  5. ChristopherDAC

    ChristopherDAC Producer

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    Okay, it's a lot simpler than it may seem.

    An SACD is basically the same, in a physical sense, as a DVD, 4.7 GB per layer, but its data format is very different, and it can optionally include a standard CD layer behind the DVD layer [on the same side -- not like DualDisc, which includes a substandard CD on the flip side].

    DVD Audio employs pulse-code modulation, in which the instantaneous value of the electrical signal representing the audio is measured repetitively, and those values are recorded. These measurements take place at a fixed rate, which has to be more than twice the highest frequency intended to be preserved; and their precision is determined by the number of bits in the binary word generated by each sample.
    So, for instance, a stereo signal consists of two channels. The DVD Audio specification allows each channel to be sampled 192 000 times per second [192 kHz], and each sample to be recorded with a precision of 24 bits [meaning that the smallest voltage step which can be differentiated is 1/16777216 of the whole audio signal, which is the same as a dynamic range of about 144 deciBels]. So, the rate at which digital data are generated works out to 2 channels * 192 000 samples per channel per second * 24 bits per sample, or 9 216 000 bits per second of audio data alone.
    Then, there are the data for error correction, and for subcodes which tell you things about the recording or display simple graphics, and for copy protection, and other purposes. The result is that the overall rate of data transfer is over 10 megabits per second, which is the maximum allowed by the DVD format. Fortunately, a company called Meridian Audio came up with a system called "Meridian Lossless Packing" which shrinks down the audio files in the same kind of way a ZIP utility shrinks down data files -- without losing anything, unlike "audio compressors" such as Dolby Digital AC-3 and dts Zeta -- but allows them to be played back in the normal way. This means not only that the high-bit-rate audio can be played back within the "1x" speed limit, but also that the playing time can be longer on the same disc.

    SACD uses a completely different encoding system called "Direct Stream Digital", in which the audio signal is measured 2 822 400 times per second, but the only information collected is whether the value is greater than or less than the preceding value, indicated by one bit which may be decribed as a sign bit -- it indicates whether the change is in the + or - direction. This process generates high levels of noise, mostly outside the range of human hearing; in fact, a 50 kHz "brick-wall" filter is standard in SACD players to avoid damaging the amplifiers they're connected to, so there's no more actual sound information than 96-kHz PCM provides. It also causes dynamic range to decrease with increasing frequency.
    Some people like it, though, and it is somewhat better in terms of most performance specifications than CD Audio. It also is at least theoretically superior to PCM recordings made and played back using a high-speed one-bit convertor, a technique which was popular for some time, and still is common in cheaper consumer equipment. SACD's main advantage from the commercial point of view is probably its insane level of copy protection.
    SACD audio, therefore, requires 2.824 Mbps of data transfer, plus overhead, per channel, so a 5-channel mix is over the DVD limit again. Sony, therefore, uses something called "DST", which is to DSD what MLP is to PCM.

    What this basically works out to is that you're not going to get much traction making audio DVDs on your PC. The best you can probably do is what's called a "HDAD", a kind of cheat invented after the DVD Video standard was published but before DVD audio was finalised: if you have DVD Video burning software, you should be able to author a DVD with a "dummy" video track, basically zero-bitrate black screen, accompanied by a stereo audio PCM track, 16, 20, or 24 bits at 48 or 96 kHz sampling frequency. This should work basically like a CD in most DVD Video players.
     
  6. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    Thanks for the indepth post Christopher. I thought Dolby Digital only went up to 384kbps and DTS up to 1.5Mbps?

    SACDs and DVD-As wouldnt work if I put them in my dvd drive on my comp right?
     
  7. ChristopherDAC

    ChristopherDAC Producer

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    Dolby Digital AC-3 and dts Zeta are completely different technologies. Both of them take a PCM signal of the kind I have described, and use various techniques -- including removing information you probably can't hear -- to reduce the bitrate from the very high figures I have quoted.

    Dolby Digital will accomodate only 48 kHz 20 bit source signals, which sets a hard upper bound to its level of fidelity, no matter how haigh a bitrate it is given. On cinema film, 320 kbps is the norm; on LaserDisc, 384 kbps; on DVD it is used for mono and stereo as well as surround mixes, but 5.1 may be between 384 and 440 kbps; I understand that it was used on D-VHS D-Theatre tapes at somethng closer to 1 Mbps, with good results.

    dts Zeta [a different codec from the theatrical version] is optimised for higher bitrates. It started out a a way to get a 5.1 mix into the 1411 kbps channel of an audio CD, and was ported over to LaserDisc without any change [replacing the CD Audio track on the LD] -- though it is worth noting that actual dtsLDs and dtsCDs use a lower bitrate, 1234 kbps, in order to avoid damaging anything if accidentally decoded as PCM [the top 2 bits of each sample are set to zero]. On DVD, dts can go up to about 1500 kbps, but is often coded at half-bitrate, about 750 kbps, which is probably not a quality improvement over DD. One upshot of this is that dts on DVDs can be made from a 24 bit 96 kHz master; "dts 24/96" [which requires fuill bitrate] is generally considered to be as close to audiophile quality as lossy compression gets.

    There are no software SACD players: SACD was specifically designed to be incompatible with computers, as a "copy protection" measure. I think there may be one software DVD-A player. In general, though, you can't put these formats in a computer drive and get any use out of them, because they're designed not to "play nice".
     
  8. LanceJ

    LanceJ Producer

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    When you all are quoting kbps figures for DTS/Dolby, is that figure for each channel (i.e. left or right or center etc) or the entire mix (left AND right AND center etc)? Thanks.

    I've successfully played a dvd-audio's Dolby track on several computers, one of which had a 5.1 speaker system with a Dolby 5.1 decoder.
     
  9. ChristopherDAC

    ChristopherDAC Producer

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    That is the total bitrate for the dts or DD stream. The channels are multiplexed together in a rather complex way -- in fact Dolby Digital AC-3 even shares bits between correlated channels -- so one cannot break them out individually very well without decoding. If you are interested, dts Zeta is designed for a target of 220 kbps per channel.

    I didn't even think about the "supplementary" audio tracks included on DVD-As -- I guess they've always struck me as a little strange.
     
  10. LanceJ

    LanceJ Producer

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    BTW: if the maker of the dvd-audio disc wants to, they can allow a player's digital output to output a high resolution PCM data stream all the way up to 192kHz/24bit.......

    ....IF the player is also designed-and configured-to do so.

    Turns out at least one-and I'll bet several- Panasonic's dvd-audio players can do this, starting with the @$90 DVD-S47. Before Best Buy stopped selling this model last year, I found this option in its extensive audio set-up menu (I was actually trying to find out if this stereo-only dvd-audio player automatically chose a disc's 2.0 channel tracks). This hi-end DAC manufacturer also realized this. They said the digital stream only exits through the coaxial output-IIRC Toslink can't handle that much data.

    Unfortunately, this is not as cool a revelation as it could be, due to the fact that the issuing of dvd-audio titles has tunred into a tiny trickle and the fact very few dvd-audio labels allow the digital signal to exit the player. [​IMG] I think only AIX and Classic Records with their DAD and HDAD discs do this.

    Confusing dvd-audio factoid: on several of my own dvd-audios, I've found that they do output a digital stereo stream, but it's always a downsampled version of a linear PCM digital stereo track, even when my Pioneer DV-656A is set to "down sampling off". No matter what the original resolution, it always seems to be converted to the 48kHz format (my receiver doesn't actually display this info, but the manual says it can't decode anything higher than 48kHz; the player also doesn't indicate the resolution: all it displays is "digital out converted"). Again, this only happens with the stereo/linear PCM tracks.

    Also, other discs still cause the player to display its digital out converted note, but I don't hear anything. Maybe it's now in 96kHz *16* bit form???

    Only my particular DTS Entertainment and Capitol discs do this; my Warner & Universal Music discs do not.

    IMO dvd-audio needs some better standards.
     
  11. LanceJ

    LanceJ Producer

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    Thanks Chris for that info. [​IMG]

    The Dolby and DTS tracks are for people who like surround music but don't care all that much about hearing it in super-duper audiophile form.* Also, for us audio nerds [​IMG] that do own dvd-audio players it's convenient to have those format(s) included so we can listen to them on portable dvd players or if we take the discs to a buddy's house equipped only with a dvd-video player.

    * and if they need to use bass management in their system
     
  12. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    So DTS can be considered better and not because of it's higher bitrate?

    I was reading a soundcard performance review and noticed they counted Dolby Digital and 5.1 as seperate things. I didn't know you could have 5.1 without using Dolby Digital or DTS. Is that no name 5.1 the system used when it comes to have a bunch of seperate analog cords instead of one? Like how some people use a couple of composite audio cords in those HTIBs and some people use a bunch of mini-rca plugs for promedia computer speakers?

    Chris it sounds to me like your saying 384Kbps isnt the bitrate limit with Dolby Digital compression and 1.5Mbps isn't the limit with DTS compression. Well now im curious. I have both dts and ac3 encoders on my comp, the dolby digital one wont let me use more then 384Kbps just like the DTS one wont let me go over 1.5Mbps, and mp3 wont let me go over 320kbps etc. Software Package issue, or something more?




    Sooooooo DD and DTS arent the only surround sound options the discs come with. What do they call the better one. What format do they use, .wav? I thought PCM was just a method used to convert an Analog signal into a Digital signal? Before I got my digital connection and got my dolby digital I used just Pro Logic II and the PCM thing always came up in the corner.
     
  13. ChristopherDAC

    ChristopherDAC Producer

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    The dts Zeta multichannel codec, at proper bitrates, is high quality, in the sense that it is practically indistinguishable from raw PCM, and that it suffers very little "generation loss" [degredation when decoded, and then re-encoded]. It is also capable of encoding from and decoding to a higher-quality source format than Dolby Digital AC-3 can accept.

    "Dolby Digital" does not necessarily mean multichannel. It is possible to have 1.0, 2.0, 3.0, 4.0, 5.0, 1.1, 2.1, 3.1, 4.1, and 5.1 configurations. Possibly the most commonly used implementation on DVD is 192 kbps 2.0 channel, which is the same as Dolby AC-2 which used to be used for analog cable/satellite broadcasts. "dts" on the other hand is designed to work as 5.1, or with certain extension 6.1, only.

    It's perfectly possible to have multichannel sound without using Dolby Digital or dts. The old "Quadradisc" vinyl records provided four discrete channels [4.0] through the proper equipment, and you can bet they were completely analog. AC-3 and Zeta are just recording and transmission formats, intended to "squeeze down" digital audio to fit it through a "narrow" conduit. Certainly if you have multiple channels of audio, you can transmit them over as many patch cords; that's not a "format", it's just a simple baseband connexion, just like the three cables you need for the Y, R-Y, and B-Y channels of component video.

    The bitrate limits you get with your encoding software are not part of the format definition, they're part of the software. It so happens that 384 kbps AC-3, 320 kbps MPEG-A, and ~1.5 Mbps Zeta are just about the most common bitrates for those codecs, but they are certainly not the maximum.

    A Compact Disc doesn't use anything like Dolby Digital or dts. It just takes straight PCM, an audio signal without any special encoding, and records it on the disc. DVD-A does almost the same thing, except that instead of two channels it can accept up to 5.1, and there is space allocated for other streams which can be played back in a DVD-V player. Again, this is not a "format" with a special name, any more than there is a special name for the audio "format" on the Compact Disc. You may find it referred to as "Advanced Resolution" audio or somesuch, but basically it is just audio data, just like a music CD.
    SACD is very similar except that it uses DSD instead of PCM.

    .WAV audio files ordinarily, but not always, contain PCM data, but they are in a computer format. The audio on a DVD-A or SACD, like the audio on a CD, is structured as a recorded stream, not as a file.
     
  14. LanceJ

    LanceJ Producer

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    Dvd-audio discs can come with all kinds of formats......

    For playback on dvd-video and dvd-audio players:

    * Dolby Digital (stereo or multichannel)

    * DTS, DTS-ES, or DTS96/24

    * PCM, but many times written as "LPCM" i.e. "linear pulse code modulation (up to the 96kHz/24bit format, though really cheapo/non-licensed players may not include the proper 96/24 decoder chip)

    And for dvd-audio players only:

    * MLP > "Meridian Lossless Packing" > 50% compressed PCM (this is not a lo-fi *lossy* format like the MP3, WMA or AAC formats). This process can be used with all PCM formats: 44.1/16, 44.1/24, 48/16, 48/24, 88.2/24, 96/24 and 192/24. This is useful to make more data space available on a disc.

    Real world example of a loaded dvd-a disc:

    Simple Minds' Once Upon A Time (here's my review)

    For a dvd-video player:

    * DTS96/24 (5.1 channels - uses the signal from a 96kHz/24bit master recording to feed the *lossy* encoder > resulting in higher frequency response when played back at home)

    * 96/24 stereo LPCM - again, most dvd-video players include a 96/24 chip to play this format (i.e. a digital-to-analog convertor or DAC). FYI: certain non-copy-protected commercial discs will allow their 96/24 signal to exit the player via its digital output.

    For a dvd-audio player:
    * 5.1 channel 96/24 MLP
    * 2.0 channel 96/24 MLP

    For the two included videos, on both dvd-video and dvd-audio players:
    * 5.1 DTS96/24
    * 48kHz/16bit stereo LPCM

    Some more recent discs also include formats like AAC so when you play the dvd-a on a dvd drive, you can load an MP3 player directly from the disc. And some discs even include .pdf files, like The Who's Tommy dvd-a, which contain the sheet music to the album.
     
  15. ChristopherDAC

    ChristopherDAC Producer

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    Yah, it can get pretty complex. The whole DVD format is like that -- only "standardised" in the loosest of senses, in an attempt [apparently] to satisfy the conflicting demands of the software producers by making life harder for the equipment manufacturers and the end users. I thought maybe I should break it down into somewhat simpler terms just because the Original Poster seemed a little confused as to what was going on.
    In any case, the PCM stream, or the MLP stream which behaves in much the same way, is the big deal; the lossy compressed stream(s), and ROM content if present, are something of a sideshow. On SACD the stereo and multichannel DSD tracks are actually stored on different zones of the disc, but I believe that DVD-A actually multiplexes them together so that they can be output at the same time [or, at least, via "on-the-fly" switching when supported].

    The basic point is, you don't need a "format" like AC-3 or Zeta to have multichannel audio. Even the original CD specification allowed for a mode of 40 minutes play with 4 channels, instead of 74 with 2.
    And, concomitantly, thinking of quality in terms of the compressed formats, with bitrate as your criterion, isn't going to tell you the whole story when it comes to audio recordings.
     
  16. LanceJ

    LanceJ Producer

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    Ken: despite all my rambling, I didn't really answer your question!. :b

    The LPCM and MLP tracks are-sonically speaking-the better sounding tracks. Their higher frequencies will especially be improved over Dolby/DTS: cleaner, more precise, with more "tinkle" [​IMG] to things like cymbals & bells; and overall the surround mixes will just have more "air" to them, in turn sounding more realistic and enveloping. Air, while not exactly scientific, for me is still the best word to describe this important effect.

    Though quite a few people report that they like the DTS tracks better because they say the surround mix is better than the MLP's surround mix, usually more aggressive they say. I'm not surprised as I also occasionally read that concerning Dolby Digital vs. DTS on a dvd movie's soundtrack (on the War Of The Worlds dvd, the insane bass that so many talk about seems to be present only on the DTS track).

    But below a certain system price point, it can be difficult to hear the *sound quality* difference between DTS, Dolby OR the LPCM/MLP tracks.
     
  17. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    Man, all this info is hard to hang onto, I gotta go over and read it all again.

    Chris, would you know what format and quality level professional sound designers store sound effects on their comp? I'm having a troublesome time. Despite my lack of knowledge I do make alot of sound effects, up until now I've been saving them as Stereo 320Kbps 44hz Mp3s, properties doesnt say bit depth so I suppose 16-bit. Never did figure out why the properties in files only displays some things and not others.

    I just recently made some war sound effects and I saved them all in Stereo at 24/192, bitrate is alittle different for each one but they're around 9Mbps. Anyway those we're saved as .wavs using Windows PCM. I seem to not have an audio codec that plays wave files, any suggestions? I can only play them in my audio editor. I have a DTS encoder but I have no codecs that actually let me hear it, any suggestions?



    Which ones better? What does a reciever say when it reads those?

    What's ADPCM?

    Chris what do you do? How do you know all this stuff?
     
  18. ChristopherDAC

    ChristopherDAC Producer

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    LPCM and MLP are exactly equivalent in quality: MLP is only a way of "packing" PCM, and it's "unpacked" to PCM in the player. There is no reciever which handles MLP. Some recievers can accept multichannel PCM from a DVD-A player, and some can accept [stereo or multichannel] DSD from a SACD player, but only via a FireWire [IEEE 1394] or HDMI connection, or sometimes USB. Most recievers will need a 6-channel analog connexion to do that. In any case, display depends on reciever; I know mine is accepting PCM because it's on a digital input and neither the "Dolby Digital" light nor the "dts" light is on: since PCM is the default, the "baseband" of digital audio, there's no need to describe it as such.

    To the best of my knowledge, the standard for professional audio mastering is now and, has been since standards emerged in the early 80s, 24 bit 48 kiloHertz sampling, and on a computer it would be stored as a .WAV file. It's only audiophile music which is recorded at 96 or 192 kHz; and only things which are going directly to CD without any editing are done at 16/44.1. There is, in fact, a special extension to the Microsoft .WAV format called the "Broadcast Wave Format" [extension .WAV or sometimes .BWF] which is the standard for pro use.

    You shouldn't need any kind of a codec to play .WAV files, since they are ordinarily [neglecting dts, DD, and MPGA coded .WAV which are rare enough] simple unpacked PCM audio data. I know I have never had a problem playing mine in Windows Media Player, VLC, Winamp, or anything else. 24/192, however, will probably not be acceptable to your soundcard or your reciever, and probably will not pass through the connexion you are using [if it is digital], and so playing them back will run into a hardware problem.
     
  19. Ken Burkstrum

    Ken Burkstrum Stunt Coordinator

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    Alright thanks for all the help Chris, probably gonna have to come back many times just to soak it all in.
     
  20. Adam Barratt

    Adam Barratt Cinematographer

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    Just to add a few snippets to what has already been posted, Dolby Digital will happily encode and decode at 24-bit resolution (Dolby, in fact, recommend using 24-bit source material when encoding), and is not base-limited in its bitrate allocation. That is, a 5.1-channel soundtrack may use bit-rates lower than 384kbps, although it is not advisable (Lions Gates' Cube Special Edition, for example, uses 224kbps for its 5.1-channel soundtrack). On DVD Dolby Digital is limited to a maximum of 448kbps, while Dolby Digital itself is limited to 640kbps (Dolby Digital on D-VHS was commonly 576kbps).

    DTS, like Dolby Digital, is capable of any channel configuration from 1.0 to 6.1 (5.1 in Dolby Digital's case). Many CDs and DVDs use 4.1, and the introduction from Spielberg on the original DTS release of Saving Private Ryan was even in DTS 1.0!

    Adam
     

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