Crystal Vision
Data packet management
TANDEM-110 User Manual R1.8
13
07/07/2010
2.1 HANC processing
Contiguous packing ensures that new audio data packets are embedded at the first free
location after the EAV in the HANC.
Contiguous packing allows for all four groups and other data, such as groups ‘marked for
deletion’ to co-exist sequentially in the HANC. For example, there is only one input audio
group present and it is specifically desired to overwrite it and there is a good reason not to
use Blank HANC.
Blank HANC removes all incoming ancillary data except EDH after the inputs have been
read and before any new data is embedded.
If an incoming audio group is the same as an audio group selected for output in that SDI
path it will normally be flagged as ‘marked for deletion’ so that downstream devices do
not detect that group. However, if there is only one audio group present in the input SDI
stream, then the HANC space is automatically blanked before embedding. This does not
remove any meaningful data, but it leaves only one audio group occupying the HANC
space.
2.2 EDH processing
EDH is in the HANC space one line per field on lines 5 & 318 for 625 and lines 9 & 272
for 525.
EDH processing may be selected to be ‘OFF’ (pass through) or ‘ON’ (include EDH
functions). EDH off/pass through disables the EDH function. When set to ON then the
EDH function calculates and inserts new Active Picture and Full Field EDH values.
If ‘Mark for Deletion’, ‘Blank HANC’ are in place then EDH CRC values will no longer
be valid. In this case, new EDH insert CRC values are calculated and inserted into the
EDH data block in each TV field.
