How passthru audio functions - Dolby E / 5.1 / 2.0, Dolby D, LPCM
The Adtec EN-30 encoder supports four pairs of audio encoding or two pairs of passthru per
service. An audio passthru consists of a compressed bitstream ( Dolby E 20 Bit / Dolby E 16
Bit / Dolby Digital / Linear Acoustic Stream Stacker 2 ) or an uncompressed stereo pair (
LPCM ) from embedded SDI passed into the egress transport stream ( IP, *RF, ASI ).
To enable Audio passthru for Audio 1:
Step Action
1
On the Audio -> Encoder 1 subtab in the Web GUI Control Application, configure
the
"Audio Mode"
for
<PASSTHRU>.
2
Configure the
“Audio Input”
for
<SDI>
.
3
Select the type of audio from the “Type” drop down. <
Dolby Digital
>, <
Dolby
E
>, or <
Linear PCM / E2
>.
note:
If Dolby E or Dolby Digital is valid at the input, the bit depth and bitrate
are automatically determined after clicking Apply.
4
On the
“PID”
tab, type in the desired Audio PID for
“Audio 1”
.
Common Passthru Problems:
Dolby E Line Placement and/or Dolby E Continuity Count Errors:
Dolby E audio compression technology is designed so that 1 Dolby E audio frame
corresponds to 1 Video frame. This 1:1 ratio of video and audio timing was designed to
assist in Video editing and seamless cuts without losing audio data. Due to the crucial and
sensitive timing, Dolby E encoders must have a reference phase locked to the video. In
other words, the SDI video timing feeding the encoder must match the same composite
reference timing that is connected to the Dolby E encoder. A simple black burst generator
that does not share the same SDI video timing will not work to source a Dolby E encoder. A
composite video reference that shares the same timing as the video source should be used.
The encoder preserves audio and video timing as it is presented. If the audio timing does
not match video timing at the inputs of the encoder, there will be line placement errors
and/or CRC errors seen on a decoder.
If Detection of Dolby E / Dolby Digital is not present, the Front Panel Quickview will show
“DE ---” or “DP ---” and the corresponding Front Panel LEDs will blink.
The encoder will automatically detect the bit depth of Dolby E ( 16 / 20 bit ) and the bitrate
of Dolby E / Dolby Digital. If Dolby E is selected and Dolby Digital is presented, the encoder
will change automatically and vice versa. If Dolby Digital is selected and Dolby E is
presented, the encoder will change the configuration automatically. If the front panel shows
dashes for the detected bitrate ‘---’, Dolby is not being detected. This is most commonly
due to a mis-configured SDI Audio Matrix or Dolby not being present on the specified input
pair. Look at the SDI signal on an SDI analyzer to verify that Dolby is present on the pair
intended. If an SDI analyzer is not available, one troubleshooting tip is to set the mode to
ENCODE. If silence or regular audio is heard on the decoder, a compressed bitstream is
