Basic outline of a large
networked digital audio facility, showing distribution
of Digital Audio Reference Signal (DARS) and data.
Digital Audio Primer/Refresher
- Encoding: From the physical to virtual
- Linear
- Pulse Code Modulation
- Sigma Delta Modulation
- Compressed - MPEG, etc.
- Up to 12:1 compression
- Requires decoding for processing or transmission
- Transmission
- Minimizing transformations
Two States, Two Paths
- Real Time Transmission: Audio as "stream"
- Good Old Analog
- Good Old Digital (AES-3)
- Brave New Digital (ISDN, WEB streaming)
- Out-of-Real-Time Transmission:
Audio as file
- Using Data Networks
- Choosing Data Networks
- AES-3 1992 (& cousins)
- Sample Rates
- The CLOCK is KING
- Distributed Audio Reference Signal, (AES-11 1997)
- ISDN
- Cascading Conversions?
- A/D-D/A-etc.
- Cascading Compression
King Chronos
- File Formats
- Transmission Protocols
- How to transport
- Sometimes it is best to stream
- Never underestimate the bandwidth of a speeding
...
- Linear
- Compressed
- ADPCM
- MPEG
- Real Audio
- Other...
- Broadcast Wave
- File Format Conversion
- Types of data transmission
- Synchronous, asynchronous, isochronous
- Shared or Switched
- Data Networks for Audio
- Ethernet and Fast Ethernet
- FDDI
- ATM
- Iso-Ethernet
- Fibre Channel and Gigbit Ethernet
- Pluses
- It's everywhere, it's here
- well understood, well supported
- really cheap
- growing, latest version is 1Gbps
- a happy IP carrier
- Minuses
- Inefficient: carrier detection, collision detection
- ill suited to isochronous data, like audio
- Pluses
- suited to any kind of data
- potentially very fast, currently 660Mbps
- highly scaleable
- Minuses
- no international standards body
- requires ATM at every point to realize efficient
throughput
- IP awkward, must fit into 53 byte cells
- Expensive and more expensive
- components &infrastructure replacement costly
- Pluses
- A device protocol AND a network protocol
- SAN architecture (Storage area network)
- Fast now, getting faster
- Subsumes legacy protocols
- Emergent standard for DV workgroups
- Minuses
- The Rocky Road to Delivery
- client is bringing interviews as 16 bit 44.1
wave files on ZIP
- Editing system is MAC based 24 bit 48kHz
- Delivery system is Separate network employing
MPEG
- Put zip in MAC convert to AIFF
- Import into SonicStudio
- Play as AES to DAT, load DAT to Dalet
- WEB access to audio product
- Dalet "Interweb", et.al.
- Can replace satellite in emergency
- satellite system for WEB transmission
- Digital technologies allow convergence of disparate
data types
- Powerful production efficiencies
- Integration with traditional IT tools
- Digital Audio transports in two states,
- streaming: AES-3, MPEG,WEB codecs
- File via Data network s
- Choose transport wisely
(Never underestimate the bandwidth of a speeding truck)
- Don't overlook analogue
- Pohlman, Ken The Digital Audio Primer,
SAMS 1997
- Watkinson, John The Art of Digital Audio
1994
- Breyer, Robert and Sean Riley Switched and
Fast Ethernet Ziff-Davis Publishing 1996
copyright 1998 by David J. Gray and npr