Additional Audio Delay (-A4 And -Aes Only); Monitoring The Audio Buffer Tracking (-A4 And -Aes Only) - evertz 7735CEM Manual

7700 MultiFrame Manual
7735CEM Composite Encoder with Monitoring
7.4.3. Additional Audio Delay (-A4 and –AES only)
Audio
Audio delay
0
-37ms to 5sec
in 0.5ms
increments
7.4.4. Monitoring the Audio Buffer Tracking (-A4 and –AES only)
Video/SID
Audio buffer
7735CEM-18
Gray background indicate un-implemented or un-tested features
In addition to delaying the audio the same amount that the video is being
delayed (in the video frame synchronizer), additional user requested delay may
be added or removed with this control.
WARNING: Both the analog audio AND the AES audio are delayed by this
amount.
WARNING: It takes approximately 1 minute, 40 seconds to adjust the audio
delay by one second. This is required by the buffer management algorithm
when changing the audio buffer size at a 1% rate without muting the audio. This
long buffer adjusting will happen on power-up or when a new user supplied
value is set with this control. However, the audio is still usable while the buffer is
being adjusted. This is good for "On-Air" adjustment of audio delays.
NOTE: Advancing audio can only happen when video is undergoing a delay that
is greater than the audio. If the system configured video delay becomes too
small, the audio buffer shrinks to it's smallest delay and stays at that value.
This item displays the status of the audio tracking buffer. It can be one of these
states:
•
Emptying (-1%)
•
Emptying (-30 ppm)
•
locked
•
Filling (30 ppm)
•
Filling (1%)
1% filling or emptying will have a slight pitch change that is near the edge of
human perception for normal audio program material. This mode will be
engaged when a large amount of delay needs to be changed quickly (video
frame drops/repeats).
30ppm filling or emptying will be used to make minor delay buffer changes.
"Locked" will indicate that the video and audio buffers match.
The delay of the audio through the audio buffer always tracks the video except
when the video frame synchronizer drops or repeats frames of video or the user
supplies a different phase of input video. Unfortunately, at these boundary
conditions, we cannot simply drop or repeat sections of audio. A rate
conversion process is used to fill or empty the buffer to the needed level. The
process must be spread out over a period of time so that the action is not
audible.
This indicator is mainly used at the Evertz factory and may also be useful to
monitor to help in debugging system issues.
Revision 1.1.1