Query the source for the latency parameters.
live will be true when this is configured as a live
source. min_latency and max_latency will be set to the difference between the running time and the timestamp of
the first buffer.
This function is mostly used by subclasses.
| this |
the source |
| live |
if the source is live |
| min_latency |
the min latency of the source |
| max_latency |
the max latency of the source |
|
true if the query succeeded. |