Sound Devices 970 - Manual (Page 27)

970 User Guide
21
Recor
ding
Sample Rate
The 970 supports the following sampling rates:
• 44.1 kHz
• 47.952 kHz
• 47.952 kHz “F” (files stamped 48 kHz)
• 48 kHz
• 48.048 kHz
• 48.048 kHz “F” (files stamped 48 kHz)
• 88.2 kHz
• 96 kHz
When Setup Menu option [Timecode/Sync - Sync Ref] is set to Internal, the sampling rate is set
from Setup Menu option [Audio - Sample Rate]. The current Sample Rate is displayed on the top-
middle Main Screen. All digital input signal is sample rate converted to the 970’s sampling rate.
External Synchronization
When Setup Menu option [Timecode/Sync - Sync Ref] is not set to Internal, the sample rate is
derived from an outside source and the setting of [Audio - Sample Rate] is not used and will not
affect the operating sample rate of the 970. The options for sync reference sources are the Internal,
Wordclock (Sync In), AES 1-2, or MADI. The 970 will only lock to supported sample rates. When an
unsupported sample rate is present at the sync reference source, the Main View label will flash and
the text will be red to indicate there is no synchronization occurring.
F Sampling Rate Modes
48.048k and 48.048kF
The 48.048kF mode (F can stand for “fake”, “faux”, or “Fostex”) is a specific compatibility mode for
use with the Fostex DV40 software (1.74 and previous), Avid, Final Cut Pro, and other post-produc-
tion environments that do not recognize audio files written at 48.048 kHz. In this mode WAV files are
recorded at a 48.048 kHz sampling rate but are stamped at 48 kHz. When played, they will play back
0.1% slower than real time.
One use for the 48.048kF mode is to force a 0.1% speed reduction (pull down) of audio to match
MOS-telecined film (24 fps-to-NTSC) in non-linear edit systems, such as Avid or Final Cut Pro. Since
the file is stamped as a 48 kHz file, the edit system will play it back at 48 kHz and not at 48.048 kHz.
This “audio pull down” will match the transferred picture without the need for an intermediate step
through other software to create the pull down.
The timecode frame rate (actual recording rate) is forced to 30 ND in 48.048kF mode. The audio file,
however, is stamped with a 29.97 ND frame rate, along the 48 kHz sampling rate. It will appear as if
the file was originally recorded at a 48 kHz sampling rate at a TC rate of 29.97 ND.
Fostex DV40
When using files recorded in the 48.048kF mode in with a DV40 with early software, set the DV40
timecode frame rate to 29.97ND. Timecode stamps will properly match the original timecode start
times.
47.952k and 47.952kF
Both 47.952 and 47.952kF settings use a record sampling rate of 47.952 kHz, 0.1% lower than 48 kHz.
The 47.952kF mode, however, identifies the file as being recorded at 48 kHz. Additionally there are
two frame rate options in 47.952kF mode. The timecode frame rate can be set to 23.97 while the file is
identified as 24ND or it can be set to 29.97ND while the file is identified as 30ND. By default, when
47.952kF mode is selected the frame rate is changed to 29.97ND and identified as 30ND unless the
Frame Rate was already set to 23.97 in which case it will remain at 23.97.
Bit Depth
The 970 records either 16 or 24 bit WAV files. The bit depth for is set from the Setup Menu option
[Audio - Bit Depth].