avsyncvideotestsrc

avsyncvideotestsrc is one half of a phase-locked audio/video test pair for measuring end-to-end A/V synchronisation. It renders a white vertical bar on black that crosses screen centre exactly on every pip instant and sweeps fully across in one pip interval, so the bar-centre crossing lines up with the tone pip from avsyncaudiotestsrc.

Each frame also carries its frame index and a phase-locked CEA-708 caption (alternating "TICK"/"TOCK") as ancillary data, so an st2038extractor can split the ANC into its own flow and a downstream analyser can check that video, audio and caption alignment survive the round trip.

Example

Eyeball-and-ear check — the bar crosses centre exactly on the beep:

 gst-launch-1.0 \
   avsyncvideotestsrc is-live=true ! videoconvert ! autovideosink \
   avsyncaudiotestsrc is-live=true ! audioconvert ! autoaudiosink

Phase locking

The content is derived purely from each buffer's running time and the shared pip-interval, so the two sources are aligned by construction and any skew seen downstream was introduced by the pipeline under test. pip-interval must be set to the same value on both elements. Set is-live=true to pace output against the pipeline clock for live capture or transmit pipelines.