There is no need for scts_set now. "Early" use of SCTS will just give the
value 0. DEBUG_EARLY_SCTS_USE can thus just check that
_superclock_ticks_per_second doesn't have the initial value of 0.
If DEBUG_EARLY_SCTS_USE somehow was set, compilation would fail because
of includes inside a namespace.
(Even without DEBUG_EARLY_SCTS_USE, any early use of superclock will
probably fail clearly with division by zero. There is thus not much need
for DEBUG_EARLY_SCTS_USE now.)
Make sure all code paths that use Temporal will initialize and reset it
properly. Some code paths (in tet runners) doesn't use Sessions, so
Temporal::reset() has to be invoked directly.
Just set the static superclock variable to 0 as initial value.
TempoMap will still be initialized early as a singleton, but we
introduce a new constructor so it is created empty (and thus not really
usable until Temporal::reset() or similar has populated it).
We can thus drop the static initialization of superclock. The default
superclock rate of 282240000 will now only live in Temporal::reset().
With this change there should no longer be any uninitialized use of
superclock_ticks_per_second(), and there should not be any problems for
DEBUG_EARLY_SCTS_USE to catch. (It is however broken in other ways -
that will be fixed next.)
This fixes various rounding issues. Notably superclock to sample
conversion must always round down when playing forward.
`::process (start, end, speed = 1)` uses exclusive end.
Processing begins at `start` and end ends just before `end`.
Next cycle will begin with the current end.
One example where this failed:
- New session at 48kHz
- Change tempo to 130 BPM
- Enable snap to 1/8 note
- Snap playhead to 1|3|0
- Enable Metronome
- Play
`assert (superclock_to_samples ((*i).sclock(), sample_rate()) < end);`
end = 177231 samples == superclock 1042118280
A grid point is found at superclock 1042116920 (that is < 1042118280).
However converting it back to samples rounded it to sample 177231 == end,
while actual location is 1360 super-clock ticks before end.
The metronome click has to be started this cycle, since the same
position will not be found at the beginning of the next cycle, with
start = 177232.
Similarly a samplecnt_t t, converted to music-time and back must not be
later than the given sample.
```
timepos_t tsc (t);
assert (timepos_t::from_ticks (tsc.ticks ()).samples () <= t);
```
IOW. When playing forward, all super-clock time between 1|1|0 and 1|1|1
should round down to 1|1|0. "We have not yet reached the first tick".
The default clock-limit is 99:59:59:00, just under 360000 seconds
(see ARDOUR_UI::parameter_changed, clock-display-limit).
AudioClock calculates this limit pos as
`timepos_t (limit_sec * _session->sample_rate())`
This caused an overflow leading to a negative value:
```
timepos_t (359999 * 96000)
samples_to_superclock (359999 * 96000, 96000)
int_div_round (359999 * 96000 * 282240000, 96000)
```
Ideally this will be optimized, here the sample-rate cancels out,
so we could use a c'tor usin seconds.
In other cases we could cache the pre-calculated sc_per_sample:
`superclock_ticks_per_second() / superclock_t (sr)` which is an
integer for all commonly used sample-rates.
Temporal::most_recent_engine_sample_rate is used in performance-critical code so shouldn't be accessed via a 'get()' function. But (via the TEMPORAL_SAMPLE_RATE #define) it does get accessed outside of libtemporal and therefore needs to get exported.
We do not want a value as large as the previous one, which limits the time
range that can be represented in 62 bits unnecessarily. The new value is
9 times smaller than the previous value, and loses only 384000 as a significant
factor.
This commit also switches to using an (inline) accessor for superclock_ticks_per_second,
making it possible in debug/testing phases to spot early/illegal uses of the value.
Now using a globally-scoped static variable which is updated by the
AudioEngine whenever an SR change occurs. Defaults to 48kHz and can
be used even before there is a backend.
When switching backends, the effective sample-rate is zero.
This only affects the butler thread (the only active thread when
stopped). The actual issue here is the butler calling
"non-realtime-stop" without a backend. However fixing 0/0
generally seems appropriate.
```
#0 in int_div_round<long>(long, long) (x=0, y=0) at ../libs/pbd/pbd/integer_division.h:36
#1 in Temporal::samples_to_superclock(int64_t, int) (samples=0, sr=0) at ../libs/temporal/temporal/superclock.h:39
#2 in Temporal::timepos_t::timepos_t(long) (this=0x7f94bc0a5890, s=0) at ../libs/temporal/temporal/timeline.h:55
#3 in ARDOUR::Automatable::non_realtime_locate(long) (this=0x55a12a980cc8, now=0) at ../libs/ardour/automatable.cc:421
#4 in ARDOUR::Route::non_realtime_locate(long) (this=0x55a12a980ae0, pos=0) at ../libs/ardour/route.cc:5462
#5 in ARDOUR::Session::non_realtime_stop(bool, int, bool&) (this=0x55a12e0cd000, abort=false, on_entry=1, finished=@0x7f94bc0a5e0f: true) at ../libs/ardour/session_transport.cc:1487
#6 in ARDOUR::Session::butler_transport_work(bool) (this=0x55a12e0cd000, have_process_lock=false) at ../libs/ardour/session_transport.cc:1153
#7 in ARDOUR::Butler::thread_work() (this=0x55a12f3b7000) at ../libs/ardour/butler.cc:222
#8 in ARDOUR::Butler::_thread_work(void*) (arg=0x55a12f3b7000) at ../libs/ardour/butler.cc:16
```
Later I'll need to push some extra changes (to support 'tempo_map_p' and 'boost::intrusive::list' etc) but these initial ones (hopefully!) won't cause any issues for the other builds.
