What is a DSP?

Discussion in 'Archived Threads 2001-2004' started by Rick_Brown, Mar 11, 2002.

  1. Rick_Brown

    Rick_Brown Second Unit

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    I believe that DSP stands for "Digital Signal Processing", but what does that mean? I generally believed that DSP's mean those usually phony sounding fake environemtns like "Stadium" and "Club", etc., where artificial reverb and echoes are added digitally to the sound.

    But, are DD, DTS or DPL2 "DSP"'s? I think not, as they don't add anything that isn't there in the signal already, but I'm not sure, as, of course, they do convert the signal into 5.1 using digital processors. Thank you.
     
  2. Adam Barratt

    Adam Barratt Cinematographer

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    From the HTF FAQ:

     
  3. Vince Maskeeper

    Vince Maskeeper Producer

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    Rick,

    You're right that for the most part DSP are the cheesy sounding ambience "soundfield" effects.

    However, DPL and DPL2 are also DSP. They take 2 channel signal and apply a processing to create multiple channels of audio. They do so using a set of complex math processes, usually executed via a DSP processor.

    Originally DPL was an essentially analog process- but in modern processors they use a digital engine to extract the matrixed audio. Technically speaking, the main designer of DPL2, Jim Fosgate, also designed DPL2 as an analog process- and the Dolby Labs people recreated his analog work in a digital chip.

    I don't think DTS or DD are technically considered a DSP (I'm not sure what the textbook definition of DSP for receivers is really, or if it has been defined)-- but one could argue it is a digital signal being processed, so it is a type of DSP. I know that Dolby/DTS have a decoder chip and d/a convertors to turn the sound into analog- but I don't know if the industry technically considers this process a DSP or not.

    -Vince
     
  4. Rick_Brown

    Rick_Brown Second Unit

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    Thank you very much, Adam. Can you elaborate on why you believe DPL is not a DSP, while DPL2 is? [​IMG]
     
  5. Adam Barratt

    Adam Barratt Cinematographer

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    Both Pro Logic and Pro Logic II are DSP functions, although neither Pro Logic nor Pro Logic II require any digital processing as such.

    Adam
     
  6. Philip Hamm

    Philip Hamm Lead Actor

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    That part of the FAQ is out of date! [​IMG]
    Digital Signal Processing is generally considered to be any digital manipulation of the original digital audio data stream. In the olden days, Dolby ProLogic was accomplished by analog singal processing. Nowadays it is accomplished digitally. Since the output, four different channels of audio information, is different than the input, two streams (a stereo stream),and the procesing happens in the digital domain, it is technically a DSP mode.
    Back in the day DSPs were frowned on, mostly because the vast majority of them frankly sounded like ass. Manufacturers would put "church", "Jazz club", "Stadium", "Hall", etc. and they mostly sounded like hell, with little more than reverb or delay (echo) added. However, even older analog only prologic receivers had these kinds of wack modes. Yamaha made a reputation largely by having good quality DSP modes instead of the ordinary wack ones. (So did Lexicon at a much higher level)
    A few DSP modes are based on industry standard algorithms, and therefore we find them "acceptable". These include The Dolby Prologic (and Surround) Familly and some others. There are some darn good proprietary solutions that turn a 5.1 signal into a 6.1 or 7.1 signal.
    The whole field of DSP modes has really changed since that part of the FAQ was written!!! [​IMG]
     
  7. Adam Barratt

    Adam Barratt Cinematographer

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    Yup, the new guy's right [​IMG] (the FAQ dates from a time when virtually the only 'legitimate' DSP was Pro Logic).
    Any digital manipulation of the original audio content is DSP processing. However, apart from a few high-profile functions such as Logic 7, Pro Logic and Pro Logic II, most DSP modes still sound pretty average.
    Adam
     

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