Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Technology Sound formats Sound formats There are many issues facing an audio professional who is considering getting into surround production, either for music, film, DVD, Internet, or multi-media. Whether you are recording, mixing, editing, or mastering, there is a lot of information that you need to be comfortable with before you can succeed in surround sound. Although this collection is a good start, it is by no means an exhaustive list or in-depth manual. Hopefully it will give you a well-rounded introduction and good foundation on which to build the pursuit of your goals. There are a number of critical issues that seem to surface every time we talk about the evolution of stereo into surround sound. Not unlike the evolution of mono into stereo, the finer points of mixing, panning, bass management, speaker placement, movie theater Vs home theater, disc formats and the alphabet soup of formats themselves, from THX to DTS to Dolby to LFE, to SACD to DVD, to DVD-A and so on, became the critical issue of the day. Speaker placement is another hot topic. Starting with the ITU suggested specifications of stereo placement. ITU: International Telecommunications Union. In surround sound, the ITU spec is referred to when talking about setting up speakers for 5.1. The ITU's guidelines are widely used and a very good place to start. To briefly summarize, they state that all speakers should be an equal distance from the listening position, with the center straight ahead, the Left and Right 30 degrees out forming a 60 degree arc across the front, and the surrounds at roughly 110 degrees. While on the subject of setting up your speakers, there are guidelines for reference levels as well. Although there is a small room spec that calls for a 79db reference, the most common is 85db for all 5 main speakers, and 89db for the subwoofer. Some Dolby certified film stages alter this slightly and reference the surrounds to 82db. You would use pink noise and measure using C weighting and slow response. This is by no means a complete guide to setting up the monitoring in your room, but it's the basics to get you started. 5.1: spoken as "five point one". This refers to a surround sound format consisting of 5 full range channels and one LFE channel (see the next entry). It consists of Left, Center, Right, Left Surround, Right Surround. 7.1. This is reminiscent of, but not exactly the same as the old 70mm soundtracks. The current 7.1 has L, C, R, LS, RS, and LFE like 5.1, but adds 2 more speakers behind the screen between the center and left, and between the center and right. These are referred to as LC and RC, or Left Center and Right Center. On large screens, this allows better tracking of dialog and effects, and more creative options for the mixers and director. The original 70mm 6-channel soundtrack had five across the front like 7.1, but no subwoofer and only mono surround. Some people have also suggested LFE: Low Frequency Effects. Typically you use a subwoofer in this application, the "point one" of 5.1. The channel does not necessarily have to be band limited, as in the option to use it as a height channel in DVD-A, but when used as an LFE, it is of course for low frequency information. It is a discrete channel, not a crossover network to derive the low frequency information from the main program. However, in most end user systems, bass management is in use, which actually does divert the sub bass from the other 5 channels to the subwoofer along with the discrete LFE channel information. THX: Tomlinson Holman experiment. Tomlinson Holman and Lucas film developed these guidelines for standardization of cinema sound systems and theater acoustics. There was later developed a standard for home playback systems and also a professional small room standard as well. The idea is that if your mix room and the playback theater are THX certified, the sound will be experienced by moviegoers as intended by the mixers and director by closely matching the sound of mix stage and movie theater. PCM: Pulse Code Modulation. This is the sampling technique that is most familiar to us as it is the basis for the CD and for most uncompressed digital audio that we come into contact with. For the CD, we take 44,100 samples of the audio every second (44.1 kHz sample rate) and quintile it into one of the 65,536 steps in 16 bits of resolution. You definitely want to read the other three installments of "Tech Talk" if you want more information about this. DSP: Digital Signal Processing. Every time you process digital audio in any way, perhaps by using EQ, dynamic range compression, or even volume adjustments, you are performing mathematical computations. The particular algorithms, dither practices involved, and other issues greatly affect the quality of the processing and resultant sound. Also, it takes computer power to do these calculations. DSD: Direct Stream Digital. This is another digital recording technique developed by Sony, originally for their internal archival purposes. It is a 1-bit recording process using a 2.8224 MHz sampling rate. It is the process used for SACD. The one bit records whether the waveform is rising or falling, as opposed to defining the exact position as in a multi-bit system like PCM. There is an 8 bit version in use for professional applications that allows proper dithering during signal processing, but this is unimportant to the end user who is delivered a finished 1-bit master of excellent audio quality. Completely different DSP methods are required for DSD as opposed to PCM. SACD: Super Audio CD. Developed jointly by Sony and Phillips, this format competes with DVD A as the next generation of better than CD quality audio delivery to consumers. While DVD has advantages in flexibility, more extras, and easy surround sound implementation, some feel that SACD, using the DSD recording process, sounds better than even 24/96 PCM audio. How it compares to192 kHz audio is less clear at the present, though some feel that PCM, by it's nature, will always be at a disadvantage. There is clearly not consensus on this point, however. PCM advocates point out many disadvantages to the DSD system as compared to PCM, so we'll have to wait and see. It is clear, however, that both DVD-A and SACD are a major leap forward from CD. It should be mentioned that SACD also has provision for including some visual extras, but not to the extent and elegance of the DVD implementation. 5.1 surround sound has been included in the goals for the SACD format, as has a red book compliant layer to provide backward compatibility with CD players. Unfortunately, these two options are unavailable at the moment and are proving difficult to provide practically, though I imagine that eventually they will work out the Kinds in one way or another. Dolby Surround: This is primarily a consumer format that adds a mono, band limited surround channel that is matrixes into the stereo audio and passively decoded at playback. The playback is compatible with stereo if you don't have a decoder. Dolby Pro-Logic: This is another matrix approach to surround, however you add a center channel to the matrix for a total of 4 channels. They are not fully discrete, nor the extra channels full bandwidth. This is similar to the "Dolby Stereo" or "Dolby SR" film release formats. Dolby SR: To music recordists and mixers it means the "Spectral Recording" noise reduction system for analog tape. To film mixers it means an LCRS surround mix matrixes into the stereo signal, and using Dolby SR noise reduction. Dolby Stereo: An earlier 4-channel matrixes surround format using Dolby A type noises reduction. LCRS: Left, Center, Right, Surround. The 4 channels in the passive matrix systems of Dolby Pro-Logic, Dolby Stereo, and Dolby SR. Dolby SR-D: This 35mm film release format has both the analog Dolby SR soundtrack and a Dolby Digital 5.1 soundtrack. If the digital soundtrack becomes unreadable or is damaged, the playback will automatically switch to the analog soundtrack. When the digital track is readable again, it will switch back. Also, in theaters that don't support digital sound, the analog track that can be read by standard Dolby SR equipped rooms. Dolby Digital: the 5.1 format that uses AC-3 compression. On DVD releases, you can have mono, stereo, or 5.1 Sound tracks with AC-3 compression recorded on the "Dolby Digital" portion of the soundtrack. The data rate is variable, with 640kbps being common on film, but 384kbps being common in DVD-V releases. Dolby EX: This is a 6.1 system that has the same channels as a 5.1 system, but adds a center rear channel. Star Wars: The Phantom Menace was the first to use this. Some consumers receivers are offering this option now, with the center rear channel matrixes into the stereo surrounds. DTS: Digital Theater Systems. Above, we mentioned DTS in the sense of it being a codec. As a codec, it compresses 6 Channels of 20 bit 48kHz audio into a data rate of 1.4Mbps for roughly a 3:1 compression ratio. It also supports a 754kbps rate for DVD. In the theater, it is actually encoded onto a CD that plays back in sync with the film and is decoded into a very high quality 5.1 soundtrack. Its debut was with the release of Jurassic Park. The third thing that you need to know about DTS is that they have a large catalog of music CDs that play back on regular CD players with digital outs. When the digital output is fed into a DTS decoder, of which several DTS equipped consumer receivers and processors exist, you get a high quality 5.1 music format. Many people don't realize that there is a viable 5.1 music format available today with a catalog of a couple hundred popular CDs available. DTS-ES: This version of DTS is a 6.1 system with a center rear channel, similar to Dolby-EX. Bibliography: Works cited Www.sospubs.co.uk www.audioxpress.com/reviews. www.itu.int Word Count: 1676
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