Nevion FRS-HD-CHO - Manual (Page 22)

FRS-HD-CHO Rev. 9
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To reiterate: The phase delay can be both positive and negative and sets the difference
between the phase of the sync input and the video output. The video delay sets the delay
between video output and video input. However, the actual delay might be longer as it also
needs to phase up to the sync input. The actual delay may be up to 1 frame longer than the
minimum video delay.
The user may specify a video delay between 2 lines (min) and 7 frames (max).
The two parameters allow a user to delay the incoming video, and reference it to the sync
input. By this mechanism, the user can precompensate processing delay in other equipment.
The video delay setting simply determines a lower limit to a 1 frame wide window into a long
delay line. The phase delay may be seen as a specification of the delay between the sync
input, and a signal "isync". The output video is always synchronized to isync. A few more
examples:
Example 1: The SDI input signal is isosynchronous to a sync signal, but 12 lines, 0 samples
delayed. The video delay is set to 1 frame, 0 lines and 0 samples. The phase delay is set to
65 samples. The actual delay between the input video and the output video will be 2 frames -
12 lines + 65 samples.
Example 2: The SDI input signal is asynchronous to the sync signal (the frame frequency is
slightly different). The video delay is set to 1 frame, 13 lines and 0 samples. The phase delay
is set to -1 line. The actual delay will gradually change between 1 frame and 13 lines to 2
frames and 13 lines. The output will appear 1 line (in the output video format) ahead of the
sync signal.
Example 3: The SDI input signal is isosynchronous to the sync signal, but 12 lines ahead of
the sync signal. The video delay is set to 1 frame, 0 lines and 0 samples. The phase delay is
set to -2 lines. The actual delay between the input video and the output video will be 1 frame
+ 10 lines.
The frames and lines are measured in units of the output SDI video standard. If the output
SDI standard is 1080i25, a delay of one line is equal to 35.5us. If the output SDI standard is
720p50, a delay of one line is equal to 26.6us. If the output SDI standard is 625i25, a delay
of one line is equal to 64us.
For a scenario where the card receives different HD video standards, (e.g.
1080i25 and 720p50) the user may want to conserve a specific delay in
microseconds for all HD video standards. This is accomplished by specifying the
delay in number of samples instead of frames and lines. (For HD video standards
the sample frequency is equal over standards, but the line and frame frequencies
are different for the different standards).
If video input disappears
Given that stable SDI input and sync input exists: If the SDI input disappears, the picture will
freeze for <hold time> and then go to video generator if the card is in default configuration.
When the SDI input disappears, the Frame Delay pulses at the back plane will also
disappear.
If video input reappears
Given stable sync input, the video will reappear after <lock time> of locked video input if card
is in default settings.
If sync input disappears
Given that stable SDI input and sync input exists: If the sync signal disappears, the card will
act as in frame delay mode, see Chapter 5.5.2.
NOTE: This will result in a frame roll as the delay changes.