DIGITAL AUDIO Basics and Overview Digital Audio Signal Processing Syracuse University, Fall 2007 Instructor: Jayant Datta A day for BASICS Basics of Audio Interconnects Basics of Sampling Analog vs Digital + Aliasing + Quantization + Jitter + Dither Basics of Audio
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Digital Audio Signal Processing
Syracuse University, Fall 2007
Instructor: Jayant Datta
“Listening studios” where a dozen people could listen to the same recording, each through a tube in the ear
Already claims of “tell the difference”Early entertainment
If in perfect condition, some people prefer the “richer” analog sound, also people find noise “warmer”
Incidentally, early recordings were done from the center outwardsPhonograph
Eight-track tapes were with us for quite a long time. 8-track was the preeminent portable and car audio format of the 1970s8 Track
Very convenient format, fits in a shirt pocket
On introduction, had three main problems: speed stability, frequency response, and background hiss
The first two were surmountable, through better tape drive mechanisms, heads, and tape formulationsCassette Tape
Information is recorded using the "helical scan" recording technique which is the same method used in VHS, Beta, and 8mm videocassette recorders.
Compared to these other formats, DAT tapes are much smaller and the information is encoded digitally.
Used for studio recording … expensive…consumer versions were less expensive
Old favorite of bootleg tradingDigital Audio Tape (DAT)
ADATs use S-VHS tapes. A 120 minute tape provides 40 minutes of recording on the ADAT.
Storage of up to 999 address locations – automation
A greatly expanded dynamic range
Elimination of tape hiss and frequency loss – generation loss
Backups of master tapes sound like the first generation master.
Perfect track separation (no track "bleed" on multi-channel mixes).
Lower cost of recording tape.
Less archiving space required.ADAT
Track and time codes are on the tape. DCC decks can locate a chosen track on either side of the tape.
The DCC 900 can digitally record music in 16-bit resolution and supports sampling frequencies of 32, 44.1, and 48 kHz
Precision Adaptive Sub-band Coding (PASC) compression to code the digital information onto tape. (4:1 ratio)DCC: Digital Compact Cassette
Durable because in diskette…no scratching
ATRAC encoding (Adaptive Transform Acoustic Coding), lossy, compression 5:1MD: Mini Disc
Sampling rate: 2.822 MHz
SACD player can play CD
4 times CD capacity
With this extra capacity, a standard Super Audio CD will provide space for 2-channel stereo data, as well as an area for up to 6-track multi-channel data, storage capacity for text and images, disc variations, copyright protection and much more.SACD: Super Audio CD