livesync

Streams incoming buffers as if they were produced by a live source, filling the gaps with repeated frames or audio silence.

Just like with identity:

• livesync can operate in single-segment or non-single-segment mode.
• livesync can synchronize outgoing buffers.

Common behaviour

• The last frame or audio silence is repeated when upstream fails to provide a buffer that meets the expected deadline.
• Late or early buffers are discarded.
• The internal loop terminates on Flush, EOS or Segment Done.

Single-segment mode

In single-segment mode, an unlimited segment with rate 1.0 is pushed prior to pushing the first buffer and keeps being used as the output segment for subsequent buffers.

• If a new segment is received, subsequent buffers timestamps are translated so their running time on the src pad (single output segment) conforms to the input segment's attributes. Note: this means that the new segment base must properly reflect the running time of its start attribute. One way to achieve this is by setting an offset on the pad pushing the event.
• Because the output segment is unlimited, input buffers are clipped according to the input segment's boundaries.
• The last frame or audio silence is repeated after clipping a buffer, until the next in-bound buffer, segment, Flush or EOS.
• The output segment rate and applied-rate are set to 1.0.
• When the input segment rate != 1.0:
  • buffer timestamps and duration on src pad are adjusted to match the expected running time.
  • For rate < 0.0, audio buffer samples are reversed. TBD: and resampled.

Non-single-segment mode

In non-single-segment mode, the output segment is the same as current input segment.

• If a new segment is received, it will be pushed downstream prior to pushing its first buffer.
• Because the input segment is also pushed downstream, input buffers are NOT clipped and timestamps, duration and samples are not modified wrt the segment rate.
• When the end of the segment is exceeded and upstream hasn't pushed EOS or Segment Done, the appropriate event is pushed downstream and the internal loop terminates.

 gst-launch-1.0 videotestsrc name=my-live-src ! livesync ! videorate skip-to-first=true ! videoconvert ! autovideosink

This will ensure that my-live-src the output has a fixed and gapless framerate.