744T User Guide and Technical Information

Recording Time Calculation

The calculation of available 744T recording time involves three factors:

•track count - how many concurrent audio tracks are selected for recording.

•data rate - calculated from the sample rate and bit depth for non-compressed audio and by bit rate for data compressed audio. Data rate determines how big the data “container” is for the audio signal (see the calculation below for determining PCM audio).

•storage medium capacity - typically expressed in GB

Uncompressed Recording Time in Track-Hours

in GB

= 1 GB)

Storage

(1000 MB

 

 

Data Rate (bit depth/sample rate), one track

 

 

16/44.1

16/48

24/48

24/96

24/192

 

(5.05 MB/min)

(5.49 MB/min)

(8.24 MB/min)

(16.5 MB/min)

(33.0 MB/min)

1

3.30

3.03

2.02

1.01

0.51

2

6.60

6.07

4.05

2.02

1.01

4

13.2

12.1

8.09

4.05

2.02

8

26.4

24.3

16.2

8.09

4.05

15

49.5

45.5

30.3

15.2

7.59

40

132

121

80.9

40.5

20.2

60

198

182

121

60.7

30.3

100

330

303

202

101

50.6

The chart above shows recording time available with the 744T. Time is expressed in hours per track (track-hours) at the specified data rate supported by the 744T. If recording two tracks, divide the track hours figure by two. Similarly for four-track recording, divide track-hours by four. Note that the 744T supports additional sample rate / bit depth combinations, however, only the most common are included below.

Record Time

The chart shows that when recording 24-bit/48 kHz audio to a 40 GB hard drive the maximum amount of recording time available roughly 80 track-hours. If recording a stereo two-track file, this yields 40 stereo hours of record time.

Note that most storage mediums now quote capacity in GB using SI units, where 1000 megabytes equals one gigabyte.

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 megabits to megabytes; multiply by 60 converts seconds to minutes.

(((16 x 48000) / 1,048,576) / 8) x 60 = 5.49 MB/min

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firmware v. 1.04 Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.