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AU-200 Digital Audio Workstations

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1 AU-200 Digital Audio Workstations
Week 1 Lecture

2 Analog Vs Digital Analog Digital
Electrical and magnetic fluctuations and physical movements, which correspond in some one-to-one fashion to the back-and- forth movement of air that we perceive as sound. Digital Defined by representations of sound waves, in the form of binary numbers (groups of 1s and 0s)

3 a. Analog Signal b. Digital Signal
Analog Vs Digital a. Analog Signal b. Digital Signal

4 Analog Vs Digital Analog recording has a conceptual edge over digital because it captures a continuous variable change in pressure. There are no discrete steps in the variance of energy levels. This system truly DOES represent the original waveform in the most accurate way. It is said that is why analog recording continues to be the mixdown medium of choice for many engineers. One problem with analog recording is noise. Even under the best of circumstances an analog recording will have a higher noise floor than a digital recording.

5 Analog Vs Digital Analog multi-tracking is also very cumbersome by today's standards. A 24-track tape recorder uses 2” tape with SMPTE time code striped on track 24 and a guard band on track 23 making it a 22-track system not 24. Analog recording machines do not have an undo feature common in the digital realm. Once a GOOD part has been recorded over it's gone. Analog masters must also be edited with a razor blade. Which doesn't always result in the BEST edits. Analog recording are also NOT consistent in quality. Each copy (or DUB or Generation) is slightly degraded from the the original. And each time the original is played it looses quality.

6 Analog Vs Digital Advantages of using digital No tape hiss
No decay when copying Can be stored on any medium Cost of storage is less expensive Storage is reliable and accurate Can be manipulated like any other data Faster transport speed

7 Digital Theory Bits and bytes
Bit : A single character in the binary (two character) language, either the digit 0 or 1. Word : A multi-digit binary number made up of bits Byte : An 8-bit word Advantage of binary code Encoding and decoding data is simple Noise does not register as audible

8 Digital Theory Sample Rate : Equates to the number of times per second that the original sound source is sampled for change in amplitude. The HIGHER the Sample Rate the more ACCURATE the system. Nyquist Law : The sample rate must be twice the highest desired frequency. Sample Depth : Is the number of bits available to the system to store EACH value sampled at the frequency rate above. The HIGHER the Sample Depth the more accurately you can define each sample point. A 16 bit word stores up to 65,536 steps where as a 24 bit word stores 16,777,216 steps. Digital Dynamic Range : The dynamic range of any digital recording system is roughly 6 times the number of bits. e.g. 16 bits x 6 = 96dB and 24 bits x 6 = 144dB Jitter : Is simply an audible timing inconsistency similar to tape flutter in the analog realm It is caused by an unstable clock. When the flow of data is controlled by and external time reference it is said to be phase-locked.

9 Digital Theory Aliasing : When frequencies are higher than half the sample rate, the samples lose accuracy. Anti-Aliasing Filters : Is a Low pass filter used to eliminate high-frequency problems before the A/D converter RAM buffer : Data flow playback rate must be constant and stable for good sound quality. The processor stores up data in RAM as and is called a buffer. It protects the system from running out of data during playback making the system run smother. Dither : At low levels digital recording systems perform poorly so white noise is added to the signal at very low levels to remove these artefacts. Noise combines with a signal to increase overall amplitude which provides greater accuracy while recording. Oversampling : The process of sampling audio and interpolating extra virtual bits between each real one. Increasing the accuracy of the sample.

10 Digital Theory Common Sample Rates:
44.1 kHz : The Standard sample rate for an AUDIO compact disc. 48 kHz : Once considered a Semi-professional sample rate until it was realized that the increase from 44.1 k to 48 k made a noticeable difference in sound quality. 32 kHz : The broadcast standard Sample Rate. Most radio stations broadcast within the limits of a 15K bandwidth. kHz : The original Sony PCM-F1 sample rate and kHz : Lower-fidelity sample rates used in computer specific documents. Used for the smaller file sizes.

11 Digital Theory and kHz : Lower-fidelity sample rates used to play back audio on older MAC computers that don't support 16-bit audio playback. 88.2 kHz : When it is known that the final product will be converted to kHz engineers will tend to use this rate. 96 kHz : A higher sample rate which will convert down to 48 kHz sample rate easily. 176.4 kHz : A higher sample rate which will convert down to 41.1 kHz sample rate easily 192 kHz : Some consider this to be the optimum recording rate. It also converts down to 48 kHz easily. 352.8 kHz and 384 kHz sample rate systems are also in the works.

12 Digital Theory Currently there are two types of digital recording methods. The most common and least expensive is PCM (Pulse Code Modulation). This simple system where a one is designated by a pulse and a zero is designated by no pulse. The other is more expensive but does provide, theoretically, for a better representation of analog sound and is called Direct Stream Digital (DSD) which uses a 1-bit binary bit stream at a sample rate of MHz.

13 Digital Theory Analog Signal

14 Digital Theory Digital sample points

15 Resulting Digital waveform
Digital Theory Resulting Digital waveform

16 Increasing sample rates
Digital Theory Increasing sample rates

17 Even higher sample rate
Digital Theory Even higher sample rate

18 I recommend using the highest possible sample rate and bit depth.
Digital Theory Choosing the proper sample rate and bit depth to record at. Final medium of product CD – 44.1 kHz, 16 Bit DVD – 48 kHz, 24 Bit Amount of storage capacity The higher the sample rate and/or bit depth the more data is stored. Clients desire I recommend using the highest possible sample rate and bit depth.

19 Digital Theory Format conversion : The process of converting between sample rates and bit depths, as well as, between basic languages like (S/P DIF, AES/EBU TDIF, etc.) The simplest of which leaves the data unchanged and just changes codes to the most complex mathematical conversions. When doing conversions it's always best to know what it's going to be used for. For Demo's and radio a lower conversion quality may be suitable but for a master recording the best conversion is always the choice. The better the conversion the more time it will take. Digital Errors : There are two types of errors in the digital domain that occur frequently: bit errors and burst errors. Errors in the LSB are probably not going to be noticed in louder passages. However, errors in the MSB can cause loud and irritating clicks and pops. Tape drop-outs or other media imperfections can cause errors in digital flow called burst errors. These are much larger and can be devastating to data conversion.

20 Digital Theory There are two methods of making CD and DVD copies.
The Replication (or manufacturing) process is similar to the way records are made. A GLASS MASTER is created from the master source recording. Then converted to a metal Father and Mother CD with pits/holes for the data. Each mother can make 20 stampers. Each stamper is then used in an injection moulding machine to stamp out CD's. This way every CD or DVD made is identical. Of course this process takes some time and is only cost effective over one or two thousand copies. The Duplication process is just like you do at home on your computer. It's the process of burning CD-R and DVD+/-R discs. This is a much more cost effect means on short runs less than a thousand. However, just like burning discs at home these can be full of errors. Therefore, each disc burnt should always be error checked.

21 Digital Audio Formats CD : Compact Disc. The standard CD holds 650 MB of audio, video or computer data. The CD RED BOOK format allows for 74 minutes of two channel (stereo) audio at a sample rate of 44.1 kHz with a 16 bit word length. CD-R and CD-RW : Recordable and Rewritable Compact Disc. SACD : Super Audio Compact Disc. Created by Sony and Philips as a higher quality replacement for the standard audio CD. SACD is stored in DSD format not PCM like standard CD. The SACD format stores 4 times the data as a standard CD and allows for the standard two channel (stereo) playback but also will playback six (6) tracks of multi-channel audio, text, images and much more. MiniDisc : Like CD's the format holds 74 minutes of stereo audio at 16-bit, 44.1kHz quality. However to get the data on such a small disc a compression scheme called ATRAC (Adaptive Transform Acoustic Coding). This scheme removes the inaudible part of each word which is assumed will be masked by remaining sound. Originally designed to replace the cassette market but was overshadowed by the acceptance of CD-R and CD-R/W formats.

22 Digital Audio Formats DAT : Digital Audio Tapes store up to two hours of stereo audio at 32K, 44.1K or 48K Hz and 16 Bits. There are newer DAT machines capable of 24 Bits. Hard Drive : Computer hard drives work in an optical manner like CD's and DVD's but have no limitations to bit depth and sample rate. DVD : Digital Versatile Disc similar to CD's but with a shorter wavelength laser which writes smaller pits. It is also a two sided disc and can have two layers per side. Single-sided, Single-Layer = 4.7GB, Double-Layer = 8.5GB, Double-sided, Single-Layer= 9.4GB and Double-sided, Double-Layer=17GB. DVD-AUDIO : DVD-Audio uses PCM encoding and Meridian Lossless Packing (MLP) for a lossless compression scheme. The format allows for up to 16 still images per song, two channel audio at sample rates of 44.1K, 48K, 88.2K, 96K, 176.4K and 192K Hz AND multi-channel audio at sample rates of 44.1K, 48K, 88.2K and 96K. In addition it allows for multiple Bit depths of 12, 16, 20 and 24 Bit words, as well as, Dolby Digital and DTS compression schemes. DVD-R Vs DVD+R : -R developed by Pioneer and is OLDER technology.

23 Digital Audio Formats DLT : Digital Linear Tape, half inch tape cartridge similar to 8mm, stores up to 70 GB of data. Mainly used for data storage. USB / Firewire Drives : USB (Universal Serial Bus) drives at up to 400mbs data through put are used for data storage and transfer. Firewire or IEEE 1394 drives are fast enough when to be used in real-time audio and video applications with through puts of 400mbs and 800mbs. MAKE SURE THAT IF YOUR RUNNING A DIGIDESIGN PRODUCT THAT YOUR DRIVE HAS AN OXFORD 911, 912, 922 OR 924 CHIPSET INSTALLED IN THE CASE. SCSI : Small Computer System Interface drives are extremely fast with wide data buses. At one time these expensive discs were all that you could use for audio or video. RAID Arrays : Redundant Array of Inexpensive Disks is an array of drives that is either striped with the data or one mirrors the other so that if one fails the data can be rebuilt quickly. Blu-Ray Disc : Designed to meet the needs of HD video can hold up to 25 GB of data. Uses a Blue-violet coloured laser rather than red like the other formats.

24 Digital Audio Formats Sound Designer and Sound Designer II : The ORIGINAL Digidesign file format used by ProTools, Session, Sound Designer and Master List CD. AIFF – Apple's Audio Interchange File Format : Apple's native audio file format up until recently only able to be used on MAC computers. WAV - Windows Audio File Format : Microsoft Windows native audio file format. This format is available on both the MAC and PC platforms. WAV files are also common in the broadcast industry when saved at 32 kHz to CD in an ISO 9660 format. BWF – Broadcast Wave File : A new version of WAV files that ads header information like artist, song title, etc. The industry STANDARD for ALL AUDIO FILES. QuickTime : Commonly used in multimedia applications and was developed by Apple. This is a lower quality audio format used for the internet. Be aware that there is a difference in the Apple saved version of this file and it does not open on any computer unless saved in web format.

25 Digital Audio Formats RealAudio : A proprietary format from Real Networks similar to QuickTime allows for streaming audio on the internet as well as playing other internet formatted files. SND Resource : Apple's internal sound system for alerts and system sounds. WMA – Windows Media Audio : Microsoft codec allowing for multi-quality audio and video to be streamed to the internet. MPEG – Motion Pictures Experts Group : MP3 stands for MPEG audio layer 3 a lossy compression scheme with multiple bit rates. While not as good as CD it has smaller files which makes it great for exchanging files when quality is not an issue. BUT ALL THIS MEANS NOTHING IF THE DATA IS LOST OR CORRUPTED. SO BACK UP OFTEN!!!

26 Digital Recording Systems
Track : Refers to a piece of digital audio that’s located on the hard drive Voice : Define the possible number of active digital tracks Take : An optional variation of a track that is much more organized Channel : A feature that refers to mixer capacity. Each track within the software system has a mixer channel Crossfade : Commonly used to blend regions together in a way that is inconspicuous and sonically smooth Audio engine : The software that defines the handling of digital audio within the computer domain. Most manufacturers optimize their products for use with their own audio engine

27 Digital Recording Systems
Pre-roll : A term borrowed from video editing. The amount of time a track rewinds before the actual edit point. Its used to get a running start Post-roll : The amount of time the mechanical or digital transport plays after the edit point. Used to hear the edit/locate the edit point quickly DSP : Digital Signal Processor a special computer processor responsible for the manipulation of digital audio data. Normally effects, EQ, normalization, time compression, expansion, dynamics, etc. are handled by the same processor that runs the computer, unless additional sound cards are added

28 Digital Recording Systems
MIDI Vs Audio MIDI - Musical Instrument Digital Interface : Is data and does not contain ANY sound. It is a 16 channel system on a 5-pin cable sending digital data such as the pitch and intensity of musical notes to play, control signals for parameters such as volume, vibrato and panning, and clock signals to set the tempo. Audio Signals : Recorded sounds from both electronic and acoustical sources.

29 Digital Recording Systems
Looping Software Vs Recording Software Vs Sequencing Software Looping software allows the user to import various audio clips at different tempos and in different musical keys and string them together. The software adapts these loops to the defined key and tempo with out drastically changing the timbre of the original. The user can usually edit the length of each clip and add effects. Recent improvements include the ability to add MIDI and record directly to the product. Recording software allows the user to use a A/D converter to record various sound sources. These systems range from simple two-track recorders to multi-track recorders capable of 100's of simultaneous tracks. Sequencing software allows the user play back MIDI files and also audio files in specific orders and for desired lengths. A GOOD DAW system will provide for most of the above. The more features the more versatile the system is.

30 Digital Recording Systems
Packages Digidesign Mark of the Unicorn (MOTU) Steinberg Apple Cakewalk

31 Digital Recording Systems
Digidesign ProTools TDM / LE / MPowered/ Academic (Mac and Windows) Industry standard in the high-end professional studio world Most expensive in the industry High quality products Have addressed the needs of the entry level market Same feel for the user interface across the board with all products Only works with Digidesign hardware Proprietary in every way Lacking in MIDI implementation but catching up Advanced features MUST be purchased Can only work with QuickTime files for video

32 Digital Recording Systems
MOTU Digital Performer (Mac) One of the first software DAWs (80s) Intuitive and user-friendly user interface Excellent and inexpensive hardware Mac only Leader in offering Firewire audio interfaces Most affordable manufacturer Excellent MIDI features Works with many manufactures interfaces

33 Digital Recording Systems
Steinberg (Mac and Windows) Creators of VST (Virtual Studio Technology) Ability to use resources from multiple computers using VST System Link Score built in Surround Mix capabilities built in Built in EQ and Dynamics Common User interface Now owned by Yamaha Excellent sound quality Use many manufactures interfaces Cubase SX/SL/SE Has been around for a while Large user base Nuendo Became a leader in features Instantly developed a loyal customer base Mainly a post-production version of Cubase

34 Digital Recording Systems
Twelve Tone Systems(Windows) Cakewalk Entry-level choice for PC/Windows users Inexpensive Plenty of features Sonar More complex and powerful First with 64 bit sound engine Built in Score Uses both DirectX and VST effects and instruments Uses many levels of interfaces Built in EQ and dynamics Excellent sound quality

35 Digital Recording Systems
Apple (Mac) Logic Pro Newest product Purchased from Emagic Leads the industry in features and capabilities Integrates with Mac hardware Includes powerful virtual instruments Good sound from plug-ins

36 Digital Recording Systems
Sony Media Software (Windows) Acid Pro Powerful loop-based program Offers some recording capabilities Loops and beats adjust to MIDI sequence tempo

37 Digital Recording Systems
Other Software of interest Live Reason GigaSampler Wavelab Fruityloops Audition Vegas Pyramix Peak Bias GarageBand Sound Forge Finale

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