This moves common code (get and fill buffers) into ::passthru()
and renames ::passthru() to ::run_route().
passthru_silence() is no longer used (it was only needed A5 style
Track::no_roll_unlocked for no-roll + disk-monitoring)
Currently ::roll() may actually be a ::no_roll() under some circumstances.
This can also happen during count-in:
transport_stopped () == transport_rolling()
and during latency-preroll:
Global session-transport speed != 0, some tracks already roll,
read data from disk and feed latent plugins.
but other non-latent tracks or busses don't roll and still have to
behave like the switch from no_roll() to roll() has not yet happened.
This changes the game WRT to monitoring as well, previously, Route:roll()
called Route::no_roll_unlocked () for conditions outlined above.
Now Track::no_roll_unlocked is called and in some cases wrongly clears
the buffers before the signal hits the disk-writer. (more work is needed
related to 61f8e53b)
On the upside this also fixes an issue with MidiTrack::no_roll not keeping
a lock while pushing data into the step-edit-ringbuffer.
This is also a step towards consolidating all entry points:
::roll(), ::no_roll(), ::silent_roll() in the Route class.
Individual Routes cannot split the process-cycle in no_roll(); roll()
by themselves. Each of the calls will flush output buffers (and offset
port-buffers). If a route feeds another route the inputs of the other
route will only see partial data.
AudioPort::get_audio_buffer() can offset the buffer simply by offsetting
a pointer. This allows to get an offset buffer for a given port.
For MIDI there's no such concept. A method writing to a MIDI buffer
which is backed by a Port can at best offset it by the global port-buffer
offset (static Port::port_offset), but not by the individual target port's
offset.
This allows to push latency upstream and delay the source
in case the destination has a longer latency.
Also add a signal to notify the Session in case this happens, intended
to queue a latency-recompute.
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...)
