Sound Devices 722 - Manual (Page 37)

722 User Guide and Technical Information
35
PCM Audio
Uncompressed digital audio is expressed numerically by two measurements, bit depth and sampling
frequency, such as 16-bit/48 kHz. These two numbers are used to compute the data rate of uncom-
pressed audio.
Audio Data Rate = Bit Depth x Sampling Frequency
In the example below the data rate of a single 16-bit/48 kHz audio stream is computed in megabytes
per minute. Division by 1,048,576 converts from bits to megabits. Division by 8 converts from mega-
bits to megabytes; multiply by 60 converts seconds to minutes.
(((16 x 48000) / 1,048,576) / 8) x 60 = 5.49 MB/min
MP3 Compressed Record Time in Hours
MP3 Data Rate (bit depth/sampling rate), stereo track
32 kb/s
(0.2 MB/min)
64 kb/s
(0.47 MB/min)
96 kb/s
(0.70 MB/min)
128 kb/s
(0.94 MB/min)
160 kb/s
(1.17 MB/min)
192 kb/s
(1.40 MB/min)
256 kb/s
(1.86 MB/min)
320 kb/s
(2.34 MB/min)
Stora
g
e in GB
(1000 MB = 1 GB)
1 72.8 36.4 24.2 18.2 14.5 12.1 9.1 7.2
2 145.6 72.8 48.5 36.4 29.1 24.2 18.2 14.5
4 291.2 145.6 97 72.8 58.2 48.5 36.4 29.1
8 582.5 291.2 194.1 145.6 116.5 97 72.8 58.2
16 1165 582.5 388.3 291.2 233 194.1 145.6 116.5
40 2912.7 1456.3 970.9 728.1 582.5 485.4 364 291.2
60 4369 2184.5 1456.3 1092.2 873.8 728.1 546.1 436.9
80 5825.4 2912.7 1941.8 1456.3 1165 970.9 728.1 582.5
100 7281.7 3640.8 2427.2 1820.4 1456.3 1213.6 910.2 728.1
160 11650.8 5825.4 3883.6 2912.7 2330.2 1941.8 1456.3 165
The chart above shows recording time available with the 722 when recording to an MP3 file. Time
is expressed in hours at the specified MP3 supported by the 722. Note that all recordings are two-
channel recordings.
Compressed Audio
When digital audio is compressed using some form of lossy, perceptual process such as MPEG2-
Layer3 (MP3 audio), Windows Media encoding (WMA), ATRAC encoding (used in MiniDisc), AAC
(MPEG-4 audio), or others - it can have a significant reduction in its data rate. Compressed audio has
enabled the practical distribution of audio over low speed data networks.
File Naming / Numbering
Files generated by the 722 are named using a syntax made up of four parts: scene number, take num-
ber, mono track designator (if mono file is selected), and extension.
scene
number
take
number
extension
mono
file
designator
S001T01_1.WAV
Post-record metadata editing can also be performed using a Mac OS or Windows based computer with
Sound Devices Wave Agent Beta.
See Wave Agent Beta for more details.