Operating instructions

GUIDE TO INSTALLATION AND OPERATION
IRD-3802 | 37
The following audio coding formats are currently supported:
• AC3 audio up to 5.1 channels
• MPEG1 Layer II
• MPEG2 Audio
The first audio can be embedded as 5.1 discrete channels (the Dolby option is required to get discreet
channels; otherwise you get 2 down-mixed channels) while the second audio is always output as 2 channels.
Down mix mode can be selected between Lt/Rt or Lo/Ro modes independently for both audios.
Audio only services can be decoded
Audio PIDs not belonging to the current service cannot be selected
Only supported audio streams will be available to the user for selection
Whenever the input signal contains erratic data, the audio decoders are stopped until the
situation is resolved. This prevents invalid data from entering the decoder and corrupting the
audio. The audio is then muted for a period of about 6 seconds.
The Dolby option must be activated to get 6 discrete AC3 channels on the SDI
The same audio PID cannot be selected for both audio decoders
4.3 MPEG AV Synchronization
MPEG transport streams normally contain information about the encoder clock system in order to genlock
the decoder to the incoming signal and avoid buffer underrun or overflows. Moreover, the audio and video
streams contain time stamps (PTS) in order to re-synchronize the stream at the output.
Should synchronization be a problem (PCR jitter, bad PTS), the MPEG clock recover system can be
manually forced to OFF. In such case, the system decoder clock is free run and frames are repeated or
dropped to cope with buffer overflows or underflows.
Setting the clock recovery in the OFF mode is particularly useful when using the Ethernet input fed by an
injection system with no flow control.
To change the clock recovery mode, go to the card menu into Input Menu, MPEG Synchro.
Refer to section 3.4.3 for iControl.
4.4 About V-CHIP & Rating Information
The IRD can translate ATSC PSIP Advisories from the EPG to standard V-CHIP inserted in the XDS of
compliant IEA-608 closed captioning data.
Because the video stream may already contain XDS advisory data, the IRD provides two modes of
operation:
Replace: Will use the PSIP information to replace any existing XDS data. Use this option if
you know you want to use the PSIP advisory.
Pass: If XDS data is already present, it is left untouched. In this mode, no V-CHIP is
generated if no XDS data is present.