Chapter 4 - Deterministic Playback - AJA Ki Pro Ultra Machine Control Manual

Chapter 4 – Deterministic Playback
The amount of time between the issuance of a normal play command and when
the device actually begins to play is variable and dependent on several factors
like the type of storage media in the device and the clip media type.
If it becomes necessary to start playback in a frame accurate manner, you can
choose to use the device's deterministic playback functionality. This functionality
assumes that the device is locked to an external video reference and the
controller is receiving this same reference. It also assumes that the controller is
timing the transmission of commands to the device at the beginning of each
frame (as determined by the video reference).
In order to arm for deterministic playback, the device must have previously been
put into still playback. If you attempt to arm deterministic playback without
having done this, the arm will fail and the deterministic playback arm enable bit
in the status will never go high.
Here is the basic strategy for using the deterministic playback functionality. This
example assumes the controller is controlling multiple devices and is making sure
they all start at the same point in time (thus ensuring all the device's playback is
synchronized).
1. Controller should cue all devices to their start timecode using the cue up
command (0x24 0x31). This will put all the devices into still playback and
parked on the frame that was given as part of the cue command.
2. Poll the status and check for one of the following:
• "Cue up Complete" flag (Bit 0, Byte Offset 2)
• "Function Abort" flag (Bit 7, Byte Offset 9)
• Timeout (5 seconds is reasonable)
If Function Abort or Timeout, this is an error condition, sync will not be
possible.
3. Wait an additional two seconds. This delay allows for the worst case of the
device coming out of EtoE mode (which will require some settling time).
4. Issue a sync playback arm command (0x20 0x08). This will setup the
device to prepare for sync playback. After this command is issued, the
"sync playback armed" status bit will be high (Bit 0, Byte Offset 0x0A). You
can clear the sync playback arming by issuing the sync playback disarm
command (0x20 0x09). This will put the device back into normal playback
mode (and still playback on the current frame). It will also clear the bit
mentioned previously. Any transport command (besides play) will clear the
sync playback arming.
5. Wait for the "sync playback ready" status bit (Bit 1, Byte Offset 0x0A) to go
high. When this bit goes high, this is an indication that the device is now
ready to accept a play command and it will be guaranteed to start with a
fixed delay.
6. Issue the play command (0x20 0x01). At this point, the device will start
playback after some fixed number of frames from the frame of command
issue. When controlling multiple devices, it is important that timing of the
play command to each device happen at roughly the same time.
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