To achieve frame accurate output at a certain time, Viz Engine utilizes a time code reader board and special commands. Viz Engine records certain commands and executes them at the exact time that the time code reader board hits the timestamp.

This section contains the following information:

Note: Viz Engine can only guarantee a frame accurate output, not a field accurate output.

Time Code Related Commands

Time Code

Description

TC*TC_INFO GET

Gives you all available time codes in the system. The return is a list of indexes and strings. Every time code source is identified by a unique index.

TC*TC_ACTIVE GET

Gives all time codes which have been updated in the last two fields.

TC*TC GET <index>

Returns the time code for the index.

TC*USED_TC GET

Returns the current used timecode by index

TC*USED_TC SET

Sets the timecode source by index.

TC*TC_COMMAND SET_TC <index> <HH>:<MM>:<SS>:<FF> -1 COMMAND

Queues a Command for execution on a specific time. 

<index>: Index of the timecode.
<HH>:<MM>:<SS>:<FF>: The timecode in Hours, Minutes, Seconds and Fields.
<#>: Command answer identifier (currently only a value of -1 is supported).
COMMAND: The Command to be executed.

Example: TC*TC_COMMAND SET_TC 1 12:07:10:00 -1 RENDERER SET_OBJECT SCENE*<9D1F7526-CFEF-C844-848279FE076E9104>

Activates scene <9D1F7526-CFEF-C844-848279FE076E9104> at exactly 12:07:10:00.

TC*TC CLEAR <index>

Clears all queued commands for the time code source with index <index>.

TC*DELETION_THRESHOLD SET <TC>

Defines a time frame after which a command is removed when it has not been executed. The threshold needs to be defined as hh:mm:ss:ff.
<TC> is a valid timecode.

Example: TC*DELETION_THRESHOLD SET 00:00:10:00

TC*ACTIVATION_THRESHOLD SET <TC>

Defines a time frame until when a command has to be executed (even if the given timecode has already passed). The threshold needs to be defined as hh:mm:ss:ff.
<TC> is a valid timecode.

TC*INSERT_THRESHOLD SET <TC>

Defines a time frame into the future during which command are allowed to be executed when inserted. The threshold needs to be defined as hh:mm:ss:ff.
<TC> is a valid timecode.

Example: TC*INSERT_THRESHOLD SET 01:00:00:00

Prerequisites

The following prerequisites are required:

  • The system must be equipped with a Plura TC Reader board. This needs to be enabled in the Viz Config File by setting TCReaderUsage = 2.

  • The correct TC source must be set by using TCReaderSource. Viz Engine supports LTC, VITC, ATC_LTC, ATC_VITC, HANC_LTC, HANC_VITC. To specify multiple sources the format would be: TCReaderSource = LTC | VITC.

  • Commands need to be sent with a timecode.
    For example: TC*TC_COMMAND SET_TC 1 12:00:00:00 -1 RENDERER*MAIN_LAYER SET_OBJECT SCENE*<9968FF26-35B0-4C01-AE5A4F8D11D1543B>. This ensures that the mentioned scene is shown on the output exactly at 12:00:00:00.

  • The Output delay should be set to a certain number of frames to prevent any frame drops (for example, to initialize clip codec, etc.).

Note: To verify this, make sure the final output device (Recorder, Monitor) can display the same timecode as attached to the Viz Engine. 

Configuration

To configure correct field accurate timeout, a few parameters need to be set. Three important values are responsible for the proper playout of Graphics, DVE Live sources and DVE Clips:

Timed Command Bias

Command: TC*TC_BIAS SET n (in fields)
Config Setting: delayed_command_bias = n

This represents the overall delay in fields, the commands are sent if the time code hits the timestamp. For instance, if your output appear two frames too late, you need to use delayed_command_bias= -2.

Note: The Command TC*TC_BIAS SET n immediately takes effect for all TC commands sent after this one, without restarting Viz Engine. 

The correct sequence to bring a scene On Air exactly at 12:00:00:00 with clips prepared would then be:

SCENE*<uuid> LOAD
SCENE*<uuid> CUE
 
TC*TC_COMMAND SET_TC 1 12:00:00:00 -1 RENDERER*MAIN_LAYER SET_OBJECT SCENE*<uuid>
TC*TC_COMMAND SET_TC 1 12:00:00:00 -1 RENDERER*STAGE START