Delay video filtering until a given wallclock timestamp. The filter first passes on preroll amount of frames, then it buffers at most buffer amount of frames and waits for the cue. After reaching the cue it forwards the buffered frames and also any subsequent frames coming in its input.

The filter can be used synchronize the output of multiple ffmpeg processes for realtime output devices like decklink. By putting the delay in the filtering chain and pre-buffering frames the process can pass on data to output almost immediately after the target wallclock timestamp is reached.

Perfect frame accuracy cannot be guaranteed, but the result is good enough for some use cases.

cue

The cue timestamp expressed in a UNIX timestamp in microseconds. Default is 0.

preroll

The duration of content to pass on as preroll expressed in seconds. Default is 0.

buffer

The maximum duration of content to buffer before waiting for the cue expressed in seconds. Default is 0.