The general goal is to align transport-sample to be the audible frame
and use that as "anchor" for all processing.
transport_sample cannot become negative (00:00:00:00 is the first audible
frame).
Internally transport pre-rolls (read-ahead) before the transport starts
to move. This allows inputs and disk to prefill the pipeline.
When starting to roll, the session counts down a global "remaning preroll"
counter, which is the worst-latency from in-to-out.
Each route in turn will start processing at its own output-latency.
Route::process_output_buffers() - which does the actual processing
incl disk i/o - begins by offsetting the "current sample" by the
route's process-latency and decrements the offset for each latent
processor. At the end of the function the output will be aligned
and match transport-sample - downstream-playback-latency (if any).
PS. This commit is a first step only: transport looping & vari-speed have
not yet been implemented/updated.
This is mostly to see if there'll be any problems when merging these changes into Mixbus. I'm guessing there'll be some conflicts in these projects (and a lot more to follow...)
After over 17 years of honorable service to the Ardour Codebase.
ClickBox and AutoSpin are retiring into the git nirvana.
We're glad for the duty, decency, reliability, dignity, respect which
these classes brought to Arodur and look back in gratitude on their years
of service.
PS. First one to say "cruft" will be fired.
Currently, the scroll handler obeys to the page increment, but instead
of using the step increment for more precise scroll, it uses an
hardcoded one tenth of the page increment.
Use the step increment instead since it has been filled with sensible
values by ArdourFader's users.
Set accumulated capture-latency for physical-outputs
and accumulated playback-latency for physical-inputs
after Ardour is done setting all non-physical port latencies.
This will be needed for latency-compensation of the complete graph.
Session::post_playback_latency() sets the actual route latency,
so that playback latency notifications need to come after capture-
latency (backends follow the same rule: capture first).
NB. Session::initialize_latencies() was already using the correct order
If disk-monitoring is disabled: disk-reader position is not relevant.
If Rec-arm is off: disk-writer position is not relevant.
But...
Play -> [plugins] -> Record
is basically a bounce and best done using the bounce operation.
(faster than realtime).
Input + Play -> Record -> Output
Ardour would need to align playback with the Input to be recorded
and at the same time align it with output, so that a player can play
along on the same track. That's not possible without a time-machine (or
a 2nd play processor).
While it can work in theory under some special circumstances, allowing
the disk-reader before the disk-writer is really just confusing,
error prone and valid uses cases are better handled by dedicated
operations.
"i18n.h" needs to be included last, after types have been defined or
clang bails out:
"call to function 'operator<<' is not visible in the template definition"
Once a session has been saved by a more recent version or a different
variant, the session file is tied to that version/variant.
The created-with version is only for debug purposes and internal use.
