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Author Topic: (?)Theatre Sound Formats For Dummies(?) Lionel Fouillen Expert Film Handler Posts: 230 From: Belgium Registered: Nov 2002 posted 04-07-2003 06:27 AM                     About screechy sound and noise reduction. Some people complain about such "screechy sound" not only with some SDDS projections but with other digital systems as well. The problem, I think, comes with sound mixers unappropriately using the full "window" of digital sound, that is a 90dB signal-to-noise ratio across a full 20Hz-20kHz frequency range. This "window" exceeds the limits of the average human auditory window, the latter being much less tolerant on the high-freq range. Hence, if recorded at too high sound pressure levels (dB), some high-pitched sound effects will appear painful to the human ear.  |  IP: Logged Evans A Criswell Phenomenal Film Handler Posts: 1579 From: Huntsville, AL, USA Registered: Mar 2000 posted 04-07-2003 07:37 PM                        No, let's not move the finer points to the afterlife yet. I provided my example, not to get into video formats, but to illustrate that digital data can be stored as analog. If someone wanted to use the normal optical soundtrack on film to store digital audio, and install a special apparatus to read and decode it, then they could do it. The digital sound could be converted to a wave form, then read by a normal sound head, and the sound output could be hooked to a device to decode the digital data. I don't know how much bandwidth one could get by doing that, but clearly a good bit of digital data could be encoded on film that way along with the image if one wanted to. In a different light: Think of how much digital data could be put on 35mm film if the entire silent aperture were used!  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 04-07-2003 07:46 PM                        How much digital info (in MB) does the sound from Dolby Digital and SDDS combined take up on a two hour movie? I wonder if you could use film prints to pirate digital data? There could be one special print encoded by an evil person at the labs to have, say, and MPEG version of the print it is shipped on sent to a special theater with an evil projectionist. The SDDS and Dolby Digital hardware could not decode the data as sound, of course. There would be super-special hardware to decode the data from the SRD and SDDS tracks back into the pirated MPEG (or maybe Adobe Photoshop or a bunch of Metallica MP3s or something). It would be worth the hundreds and thousands of dollars it would cost.  |  IP: Logged Christopher Seo Jedi Master Film Handler Posts: 530 From: Los Angeles, CA Registered: Jun 99 posted 04-08-2003 02:36 AM                     Regarding "track" and "channel": Fortunately, I have been able to reconcile Michael's and Manny's definitions of "track" and "channel". Both are correct, but we must clarify a semantic distinction when speaking about digital sound. With analog sound, Manny's original definitions hold with no further elaboration: a discrete channel of analog sound requires a physically discrete track, i.e., one recorded physically separate of the others. However, the nature of digital data inherently requires reconstitution of the sound (or any) information into analog form for ultimate perception by humans, and as such, the data representing discrete channels of sound can be in any physical format-- intertwined, as it were. In fact it is advantageous to do so for error correction purposes (e.g. SRD, and I'd assume SDDS). In this sense, the analog notion of "track" evolves, taking on more of an abstract meaning. A "track" of sound is not simply a physically separate sound recording, as in the visually obvious case of optical Lt and Rt; it is a conceptually discrete delivery path for sound, as intended by the mixers, which the digital circuitry is programmed to reconstitute individually and separately, as if no other sound paths existed. In other words, we should distinguish "soundtrack" from "track". A "soundtrack" is the physical total of the recordings which constitute a whole, and a "track" is a discrete sound path which can be read off a soundtrack. Evans: I don't understand what you mean by your idea. Are you suggesting that a digital soundtrack could be put into the optical analog soundtrack area in addition to the analog track, or in place of the analog track? Regarding SDDS sounding "screechy": There was a FHF discussion on the hf deficiency of SDDS pink noise here.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 04-08-2003 05:54 AM                        The SDDS pink noise is not "deficient". It is just right for alignment of the sound hardware which has a better high frequency defintion. If done right, an SDDS systems sound clearer and crisper than some other formats which have a more diffuse high frequency playback playback perceived as "softer". Interesting defintions found here. channel: 1. A connection between initiating and terminating nodes of a circuit. 2. A single path provided by a transmission medium via either (a) physical separation, such as by multipair cable or (b) electrical separation, such as by frequency- or time-division multiplexing. 3. A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths. 4. Used in conjunction with a predetermined letter, number, or codeword to reference a specific radio frequency. 5. The portion of a storage medium, such as a track or a band, that is accessible to a given reading or writing station or head. 6. In a communications system, the part that connects a data source to a data sink. track: On a data medium, a path associated with a single read/write head position as data move past the head. digital: Characterized by discrete states. analog data: Data represented by a physical quantity that is considered to be continuously variable and has a magnitude directly proportional to the data or to a suitable function of the data. Evans was right about the Laserdisc.  |  IP: Logged Evans A Criswell Phenomenal Film Handler Posts: 1579 From: Huntsville, AL, USA Registered: Mar 2000 posted 04-08-2003 03:27 PM                        quote: Evans: I don't understand what you mean by your idea. Are you suggesting that a digital soundtrack could be put into the optical analog soundtrack area in addition to the analog track, or in place of the analog track? Use the existing analog track to record digital data as sound. (Like a modem converts digital data to sound to travel over a phone line, or like how digital audio data is converted to analog to be stored on Laserdisc). That way, you'd use the same sound recording and sound reading design -- you'd just preprocess before recording and postprocess the sound read from the film to get the digital data encoded. Or an even more interesting idea: I could imagine a digital sound format working as follows: Record a mono version of the movie in normal optical sound using one of the analog tracks (say the left channel, for example) and record the encoded digital sound on the right as audio. The stereo reader in the theatre could read the left track and use it as a mono soundtrack if the theatre didn't have the digital decoder. If the theatre had a digital decoder, the right track could be read and fed to the decoder, which would produce digital sound. The left mono in normal analog style could be used as a backup in case the digital became unplayable. I am sure that this option was considered at some point when digital sound for film was being developed.  |  IP: Logged

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