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Instruction Manual: evolution 5000 E57xx DSNG and DENG Voyager Encoder Page 4-63
ST.TM.E10076.3
RF Protection Option
NOTE…
This option is only shown when the Coding Standard is Dolby Digital (AC-3).
To access the RF Protection option, press the RF Protection softkey in the
Audio A Menu. The option can be turned On (with RF Protection) or Off
(without).
RF Overmodulation Protection is used in situations where the audio signal
of a decoded AC-3 bit-stream is delivered via a link with very restricted
dynamic range. One example is the case of a television broadcast, where
sound is modulated onto an RF channel and delivered to a low cost
television Receiver.
In this situation it is necessary to restrict the maximum peak output level
to a known value with respect to dialogue level, in order to prevent
overmodulation.
Deemphasis Option
NOTE…
This option is shown when the Coding Standard is Dolby Digital (AC-3) or MPEG Layer 2.
To access the Deemphasis option, press the Deemphasis softkey in the
Audio A Menu. This parameter is used to de-emphasise the
pre-emphasised audio.
To meet the specifications of the audio encoding algorithms (MPEG/AC-3),
the audio input signal must not have any pre-emphasis applied. If the
input signal does have pre-emphasis, a de-emphasis filtering process must
be applied prior to encoding.
For a digital audio input, pre-emphasis detection is typically achieved by
monitoring the pre-emphasis flags within the channel status data of the
incoming digital audio signal. This is adjusted automatically by the Encoder
when it is set to Auto.
For an analogue audio signal, the user must manually enable the
appropriate de-emphasis filter accordingly.
The displayed options vary according to the audio Source and Coding
standard.
The options for AC-3 are: Off, Auto, On. Auto applies to digital only.
The options for MPEG-1 are: Off, 50/15 µs, CCITT J17.
DC Filter Option
NOTE…
This option is only shown when the Coding Standard is Dolby Digital (AC-3).
To access the DC Filter option, press the DC Filter softkey in the Audio A
Menu. This parameter is used to activate a dc high-pass filter for all input
channels. The option can be turned On or Off.