3-Digital Audio - Delivery REV

3-Digital Audio - Delivery REV
Digital
Delivery Media
Compact Disc History
1978
Philips & Sony launch the Compact Disc using a fully digital
recording and replay system
1981 – CD released in Japan
Billy Joel’s Songs From The Attic (first digitally-recorded live
album; produced by Phil Ramone
1982
52nd Street - first album made commercially available on CD.
Compact Disc History
1983
CD released in Europe, US, etc
1985
Dire Straits Brothers In Arms spurs sales of CD players in England
1988
CD sales surpassed LP sales, CD and cassette are the two dominant consumer formats.
CD FORMATS
CD-Audio (Red Book)
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~74 minutes of audio @ 44.1 kHz/16 bits; 20Hz - 20kHz
CD-ROM (Yellow Book)
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700 MB of graphics, video, digital audio, text, data, etc.
CD-R (Orange Book)
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recordable
Enhanced CD (Blue Book)
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‘CD-Extra’, contains both CD-Audio and data
Compact Disc How it Works
•
CD’s are Optical Disk; a laser is used to read data from them
•
Both store binary as non-reflective pits on the disk
•
During Manufacture these pits
are pressed into the plastic
•
The Raised areas around a pit,
called lands, are reflective
CD Capacity
The format for CD-Audio…
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5-inch disc
700 MB Capacity
transfer speed of 1.4 megabits/sec.
Approx. 80 min. of play time
2 audio tracks (Stereo)
44.1 kHz audio/ 16 bit
DIGITAL VERSATILE DISC (DVD)
1995 Sony and Toshiba develop a DVD standard for presenting digital video and audio to the consumer.
The format for DVD-Video...
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5-inch (12cm) disc (same as CD)
4.7 GB per side (7 x CD’s)
transfer speed approx. 6 x CD.
> 2 hours per side w/ video and audio
8 audio soundtracks
48.0 kHz audio
DVD-ROM for computer data (applications, etc.)
Differences in Disks
DVD uses a narrower laser beam to read disk
• This results in smaller and narrower pits than a CD
• Smaller pits mean larger storage capacity
DELIVERY MEDIA: DVD-A
1998 DVD-Audio introduced
✓ same capacity as DVD-Video
✓ audio sampling rate up to 192 kHz
✓ higher transfer rate for audio only
✓ high quality audio storage format (variety of channels, sampling rates, word lengths,
etc.)
DELIVERY MEDIA: SUPER AUDIO CD (SACD)
1999 SACD introduced by Sony/Philips
✓ physically the same as DVD disc
✓ uses a process known as Direct Stream Digital (DSD) at the sampling rate of 2.8224
MHz to allow high quality audio in stereo and 5.1
✓ can incorporate a CD layer for compatibility with CD-Audio players (called ‘hybrid’
disc)
✓ high quality audio storage format (variety of channels, sampling, word lengths, and
etc.)
Digital discs…and Format Wars!
More clashes…and a winner!
DELIVERY MEDIA: BLU-RAY
2004 introduced by Blu-ray Disc Association
✓same physical size as DVD disc
✓ capacity 25 to 50 GB; transfer rate of 54 Mbits/sec
✓multiple standard video formats
✓multiple standard audio formats include: lossy and lossless data
reduction
✓used for data storage, 1080p High-definition video, Highdefinition audio, stereoscopic 3D!
Digital Audio
Data Reduction
Data Reduction
✓ A data reduction system will decrease the audio data/bit rate
✓ Data rate = sampling frequency x word length x # of channels
File Sizes for a One Minute Audio Clip
Sampling Rate
Resolution
No. of Channels
Bit-rate
File Size (Bytes)
44,100
16
2
1,411,200
10,584,000
44,100
16
1
705,600
5,292,000
22,050
16
2
705,600
5,292,000
11,025
16
2
352,800
2,646,000
11,025
8
2
176,400
1,323,000
Data Reduction
Two (2) basic categories of data reduction:
✓ 1. Lossless
✓ Encode repetitive data in less space with no data removed
✓ Original can be reconstructed exactly
✓ Uses a codec (compression/decompression)
Examples of losslesscodec:
MLP (Meridian Lossless Packing) used on DVD-Audio - 2:1 reduction
FLAC (Free Lossless Audio Coding) - 2:1 reduction (e.g.HDTracks)
ALAC (Apple Lossless Audio Coding)
Data Reduction
Two (2) basic categories of data reduction:
✓ 2. Lossy
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Discard unnecessary and redundant info; use perceptual techniques
**Apply lossless techniques for further file size reduction**
Reconstruction not exact but close enough to represent original
Use a codec (compression/decompression)
Examples of lossy codecs:
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Dolby Digital / DTS
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MPEG (e.g. MP3) - most common for downloads (10:1)
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AAC (Advanced Audio Coding)
Data Reduction
Various compression (data reduction) ratios and their effect on storage needs:
Streaming
✓ Pandora
✓ uses AAC
✓ 64 / 128 / 192 kbps
✓ Spotify
✓ uses Ogg Vorbis
✓ 96 / 160 / 320 kbps
✓ Tidal
✓ uses AAC
✓ 96 / 320 / FLAC
Downloads
✓ Apple
✓ uses AAC
✓ 128 / 256 kbps
✓ MP3.com
✓ uses mp3
✓ 128 / various kbps
✓ HDTracks
✓ AIF, WAV, FLAC, ALAC
✓ 44.1 kHz +
Transmission / Distribution of Digital Audio
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