Sync Out CHOP

From TouchDesigner 099 Wiki


The Sync In CHOP and Sync Out CHOP are used to keep timelines in two or more TouchDesigner processes within a single frame of each other. One process will contain a Sync Out CHOP while one or more other processes contain Sync In CHOPs. In addition any CHOP data sent through the Sync Out CHOP is received by the Sync In CHOPs. The CHOPs synchronize by pausing their own timeline until all Sync In/Out CHOPs have cooked. The Sync Out CHOP will be ahead of the Sync In CHOPs. If any CHOPs fail to communicate, the others will timeout, causing all processes to run slowly. The processes with Sync In CHOPs should have their Realtime flag checked off, as their frame rates will be determined by the Sync Out CHOP.

Client machines may come online at any point, or be switched off as desired, as the Sync Out CHOP will adjust accordingly, either timing out, temporarily or permanently banning individual clients as specified.

NOTE for Windows OS - If experiencing connection issues make sure Windows Firewall is disabled.

An Info DAT, pointing to the Sync Out CHOP, provides a detailed list of all clients:
The columns are are:

  • pid: process id of the client
  • address: ip and port number
  • machine_name: client machine name
  • filename: name of the toe file the client resides in
  • op_path: full operator path to the client
  • include: when 1, the Sync Out CHOPs waits for a reply, when 0, it is ignored.
  • timeout_total: The total number of times the Sync Out CHOP stalled waiting for this client
  • timeout_consecutive: The running number of times the Sync Out CHOP stalled waiting for this client.
  • steady_total: The total number of times the Sync Out CHOP received a reply in time.
  • steady_consecutive: The running number of times the Sync Out CHOP received a reply in time:
  • reply: The last reply from the client, all clients should have the same increasing value.

Similarly, an Info CHOP will reveal further information, such as:

  • sync_incompletes: This number is constant when the system is in sync, and will climb up each time the number of clients responding does not match the expected number. When all is steady, the number does not change.
  • sync_internal: The number of clients within the same toe file that it is waiting on.
  • sync_external: The number of clients from different toe files that it is waiting on.

Intermittent Connections

Whenever a client replies, it is immediately assumed reliable, and waited upon, by the Sync Out CHOP each frame thereafter. When a client times-out a number of times in a row, however, it is continuously ignored by the Sync Out CHOP, until it replies on time again. This also applies to clients that have stopped communicating altogether. The number of consecutive timeouts is controlled by the Client Timeouts (consecutive) parameter and is reflected by the timeout_consecutive Info DAT column.


If a client produces unreliable communication, sometimes steady, sometimes timing out, then it can be permanently ignored by enabling Ban Clients and setting the Total Timeouts accordingly. Once a client timeouts a certain number of times, its Info DAT include column reports banned and it will always be ignored, even if it starts responding in time again.


Whenever the Sync Out CHOP first starts any and all clients are accepted, and nothing is banned. Pressing Clear Stats in the Sync Out CHOP also returns to this state, clearing all banned lists, and totals, even in the remote client Info CHOPs.

See also Syncing Multiple Computers and Hardware Frame Lock.

PythonIcon.png syncoutCHOP_Class

Parameters - Sync In Page

Active /active - Whether or not the CHOP is currently attempting to synchronize itself.

Multi-cast Address /multicastaddreess - An IP address to communicate on (

Network Port /port - The network port associated with the address.

Timeout (msec) /timeout - The maximum amount of time the CHOP will wait for synchronization signals from the other Sync CHOPs. This value is expressed in milliseconds.

Client Timeouts (Consecutive) /timeout - The maximum number of consecutive timeouts a client must generate until it is ignored, causing no further timeouts. It will remain ignored until it replies on time again or this CHOP is reset.

Ban Clients /banclients - Enables permanent banning of clients.

Total Timeouts /banclienttimeouts - The maximum number of timeouts a client must generate until it is permanently ignored. Only a reset will allow it to be included again.

Clear Stats /clearstats - Pressing this button will clear all banned lists, as well as totals reported in an Info CHOP.


Use an Info CHOP to monitor the status of the connection. The channel named sync_incompletes will increment by one each time the group of Sync CHOPs are unable to synchronize.