2 signal flow, 3 asynchronous data transport, 1 4.5 top view – Nevion AV-3G-XMUX User Manual

Page 9: Signal ﬂow, Asynchronous data transport, De-embedding, 2 signal ﬂow

Introduction

AV-3G-XMUX User Manual Rev. B

All 8 audio groups are de-embedded from 3G video both in layer A and layer B. The audio signals

are available in the audio matrix which is considerably expanded in this mode.
The four audio groups that are not embedded by the module will be transported without any

delay. This means that the use of the module with diﬀerent video formats will be predictable. If

the module is to be used to embed the extra 3G audio signals then it will transport the normal 4

audio groups transparently. If SD or HD video is then fed to the same embedder, the embedders

will be disabled. De-embedding from the normal groups will be performed as before.

4.2 Signal ﬂow

Video may be presented on the optical or electrical inputs. The module will switch to the other

input if the module can not lock to a signal. The video is re-clocked and transformed to paral-

lel video. The parallel video goes into a line buﬀer which is used to de-glitch the video when

switched on the correct line. No errors are ﬂagged or produced when the video is switched on

the appropriate switching line. All ancillary data, including embedded audio is extracted from

the video signal. All the packed data is sent to the group router. The de-embedded audio is sent

to the stereo audio cross-point router. The AES audio inputs are initially connected directly to the

audio router. Sample rate converters are inserted if there are sample slips or the signal is not a

data signal. The use of the sample rate converters may be disabled. See chapter 3. Four of the

router sources are from the mono shuﬄer. Each input may be any of the de-embedded signals

or the AES input signals. The audio signal is delayed by a few samples during de-embedding,

re-packeting the audio and audio processing. Signals that pass through the stereo audio router

will be delayed by a small number of samples. The group router outputs from the de-embedders

do not introduce any additional delay as the audio does not require unpacking and re-packing.

The embedder core embeds either re-packeted audio from the stereo router or the existing de-em-

bedded audio as conﬁgured in the group router. The embedded audio packets are inserted into

the video signal together with the control packets and any other packets that were present in the

original video signal. The video is serialized and output through the cable and laser drivers. The

AES audio output signals are taken from outputs of the audio router.

4.3 Asynchronous data transport

Data signals are transported using the user (U) bits in AES audio streams. The de-embedding and

embedding is performed in the AES audio router core. Any input in the router core may be chosen

for data de-embedding and any router output may be used to embed data. See section 3.5.

4.3.1 De-embedding

The module receives many AES signals and data may be present on any of them. The user must

conﬁgure which AES signal the data is expected to be on. The status page in GYDA will show the

presence and the type of data detected on the conﬁgured channel. De-embedded data is output

on the RS485 backplane output.