Instruction manual

HDE-3000 - 37 -
5.1.3 Com 2 Setup Menu
This menu lets you set the HDE-3000 to receive or send closed caption data via its RS-
232 serial interface, com port 2. This menu has the same functions as com port 1 setup
menu.
Warnings
o The raw data encoding modes take control of the field one and/or the field two data
encoders in the HDE-3000, preventing any other function in the HDE-3000 from
obtaining control of the field one and/or field two data encoders. To allow other functions
(such as the caption file encoder) to operate properly, the raw data encoding functions
must be disabled by setting the com port function to “disabled” or the “parser mode” to
“normal”. If you attempt to run a caption file, and the raw data encoder has control of the
encoder, then the caption file will not encode and you will receive the error “Error 170
Starting Job”.
o The bridging process causes a delay in the captions, and the delay is typically one frame
(two fields). Typically there are a few milliseconds of delay caused by decoding
equipment that reads the EIA-608 data from the video and transmits the data out a serial
port. Then there is another few milliseconds of delay caused by the serialization of the
data across the serial cable (dependant on the baud rate). Then there is another few
milliseconds of delay in the HDE-3000 in the process of receiving the data and getting it
ready to be encoded in the proper field. Typically, the raw data decoded from one frame
of video makes it into the HDE-3000 in time to be encoded into the following frame of
video.
o If the equipment being bridged causes more than two frames of delay then the video
being fed to the EIA-608 decoder must also be delayed to prevent the line 21 captions
from being re-encoded too early.
o There are four bytes of EIA-608 data per frame of video (two bytes in field one and two
bytes in field two). For NTSC video there are 29.97 frames per second (59.94 fields per
second). This equates to a serial baud rate of approximately 1200 baud (approximately
600 baud for field 1 plus 600 baud for field 2). In order to prevent serial port overruns, it
is necessary to use a baud rate higher that 600 for one field of data and higher than
1200 for both fields. A baud rate of 9600 or higher is generally recommended for
bridging to minimize the delays described above.