Aes User Bits; Sample Rate And Audio Bandwidth; Subframe Delay - Orban OPTIMOD 6300 Operating Manual

OPTIMOD 6300 DIGITAL
Because the 6300's digital input is equipped with a sample rate converter, an asyn-
chronous digital input can be applied to the 6300 while its output is synchronized to
a master sync generator.

AES User Bits

In Setup, you can configure the 6300 to either block or pass AES User Bits from its
digital input to its digital output.

Sample Rate and Audio Bandwidth

Most DAB audio is at 48 kHz sample rate. However, the iBiquity™ HD-AM™ system
operates at 32 kHz, requiring 15 kHz audio bandwidth. The Eureka-147 system of-
fers a 24 kHz sample rate option, requiring 10 kHz audio bandwidth. The Digital Ra-
dio Mondiale (DRM) system also allows reduced audio bandwidths and sample rate
for speech-grade services.
OPTIMOD 6300's bandwidth can be adjusted from 10 kHz to 20 kHz to provide cor-
rectly anti-aliased audio for any of these systems. As long as any anti-aliasing filters
following OPTIMOD 6300's output are phase-linear, these filters will pass the band-
limited OPTIMOD 6300 output without introducing overshoot because they remove
no further spectrum and do not add group delay distortion.
The bandwidth-limiting filter is located before the processing, so it affects all out-
puts equally.
OPTIMOD 6300 always operates at 48 kHz sample rate internally, except for its peak
limiters, which operate at 192 kHz to prevent overshoots following D/A conversion
or sample rate conversion. The 6300's output is equipped with a sample rate con-
verter that can output at 32 kHz, 44.1 kHz, 48, 88.2, or 96 kHz. These rates can be
synchronized to the 6300's internal clock, its AES3 digital input, its AES11id input, or
its wordclock input.
We expect that transmitters that transmit sample rates below 32 kHz will provide
internal sample rate conversion, and that most will probably accept audio at 48 kHz
sample rate regardless of the final sample rate of the transmission. To prevent over-
shoots due to spectral truncation, the 6300's lowpass filter cutoff frequency must be
set to complement the frequency response of such links.

Subframe Delay

OPTIMOD 6300 provides an adjustable time delay of up to 96 milliseconds. This al-
lows the installer to force the total delay through the processing to equal one frame
(in sound-for-picture applications). The definition of "frame" depends on the system
in which OPTIMOD 6300 is installed.
The selections are
monochrome video), 29.97 fps (NTSC color video), 25 fps (most PAL
video), and 24 fps (film). You can also adjust the delay in one-millisecond
increments from 15 to 96 ms.
M
INIMUM
(approximately 24 ms delay), 30 fps (NTSC
1-19
INTRODUCTION