Nevion SDI-TD-3GMX-5 - Manual (Page 11)

HD-TD-3GMX-2 / HD-TD-3GDX-2 and SDI-TD-3GMX-5 / SDI-TD-3GDX-5 Rev. F
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The HD-TD-3GMX-2 can receive any combination of two HD or SD video standards,
synchronous or asynchronous. The HD-TD-3GMX-2 embeds timing information that the
HD-TD-3DX-2 uses to regenerate the HD or SD signals with the same clock frequency as
the original inputs. The two signals are treated as two completely independent streams,
which means that there will be no cross-contamination of the other stream when one input
goes missing or has inherent errors.
The output from the HD-TD-3GMX-2 module is either electrical 3G-SDI according to the
SMPTE 425M standard, or if an optional laser module is added, simultaneous electrical and
optical 3GHD-SDI according to SMPTE 297-2006
If the customer has purchased an optional long haul or short haul receiver module for the
DMUX side (in which case the DMUX module will have an “R-L” or “-R” appended to its
name), there will be an option available to select either input manually, or to select between
them automatically.
4.2 The SDI-TD-3GMX-5 and SDI-TD-3GDX-5
The SDI-TD-3GMX-5 has two distinct modes of operation, set by the user: Either the same
two-input mode described above for the HD-TD-3GMX-2 / HD-TD-3GDX-2, or a mode with
up to five inputs, where only the first one can be HD-SDI. The latter mode is really the same
as the first, but with the addition of a 4xSD-to-1xHD software module from the SDI-TD-
MUX-4. This means that the HD stream normally coming straight from input 2, will now be
replaced with a multiplex of four SD-SDI inputs. This in turn means that input 2 can only
handle SD-SDI input signals in this mode, not HD-SDI. The user selection of the two modes
will prevent the possibility of overflowing the 3GHD-SDI carrier stream.
On the de-multiplexer side of the 3G transport link, the card will be able to read control
words embedded in the transport signal to determine which mode it should operate in. No
user control is necessary on the de-multiplexer side. The SDI-TD-3GDX-5 fully supports
input from both the SDI-TD-3GMX-5 and the HD-TD-3GMX-2, whereas the HD-TD-3GDX-2
will only be able to recover the signals for outputs 1 and 2 if fed a signal from an SDI-HD-
3GMX-5.
4.3 HD ancillary data limitations
Because the total usable transport bandwidth in the 3G output of the multiplexer is slightly
less than that of two full HD streams, a small number of samples must be dropped from the
incoming horizontal blanking intervals. The active picture will never be affected.
The number of samples dropped varies depending on the HD format as shown in Table 1.
Samples will be removed from the tail end of the HANC, following a left-alignment of all
valid packets. Given typical HANC payload size, such as required to carry AES audio, the
sample deletion will have no impact as it will occur entirely in unused samples.
In the case of an unusually full HANC, such that sample deletion would result in a
fragmented HANC packet, the remaining fragment will be deleted to maintain SMPTE
compliance.
HANC data that are not contained within a valid SMPTE 291M packet are not guaranteed to
be transported, and ma
y appear as null or ’black’ values when de-multiplexed.
There are no limitations to the active video area portion of the HD signal to be
transferred
– this will always be restored to its original content at the receiving
end of the link, as long as it is a valid video signal according to applicable
SMPTE standards.