In hardware-low-latency mode, signals are supported that indicate how much an input or output frame has been filled. The encoder can suspend waiting for more data to become available. Also, a frame can be skipped when encoding is running behind.
The VCU2 encoder interprets an eol hardware signal that is signaled every 16 pixel-lines
and an eof hardware signal marking the end of a frame.
This, together with a frame index specifying the frame the encoder is working on, allows
the encoder to suspend operation waiting for more data to become available. When using
hardware low-latency mode there is a limit of one stream per encoder core (2 are available per VCU2 tile).
This requires the software to send a frame downstream before any data is captured or decoded.
A VCU2 decoder core outputs a 14-bit counter that indicates the progress in number of pixel-lines (in units of 4 pixel-lines). When using hardware low-latency mode there is a limit of one stream per decoder core (1 available).