GUIDE TO INSTALLATION AND OPERATION
IRD-3101 |
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The following audio coding formats are currently supported:
•
AC3 audio up to 5.1 channels
•
MPEG1 Layer II
•
MPEG2 Audio
•
AAC audio (2 CH only)
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. Downmix mode
can be selected between Lt/Rt or Lo/Ro modes independently for both audios.
The secondary audio can be set in pass-through mode for AC3 data stream. This allows embedding raw AC3
streams on channel 7 and 8 of the SDI signal.
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
Audio 1 is embedded on AES channels 1 to 6, Audio 2 is on channels 7-8
The Dolby option must be activated to get 6 discrete AC3 channels on the SDI
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 (frame buffer mode).
Setting the clock recovery in the OFF mode is particularly useful when network jitter is important and the video sync or
audio sync status of the IRD keeps blinking.
To change the clock recovery mode, go to the card menu into
Input Menu
,
CLOCK RECOVERY
Refer to section 3.4.5 for iControl.
The audio video synchronization can be further improved with firmware revision 301 and up. A new setting called AV
sync quality allow the user to achieve better AV sync when set to BEST. The BEST setting will deliver AV sync within
1ms but requires the input TS to be completely free of errors. If errors are present in the TS, the video and audio may
become out of sync. The synchro system will then restart the audio decoder to reach sync and this will cause a mute
in the audio. This feature must be used only in error free environments.
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:
