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authorRobin Gareus <robin@gareus.org>2013-07-09 13:13:27 +0200
committerRobin Gareus <robin@gareus.org>2013-07-10 15:27:15 +0200
commitee97942165fbbd82eb7453f2e74f6f06a1974a44 (patch)
treebfd17b722fb51738b1cf45c2ac6255a61b4f96d9 /libs/ardour/meter.cc
parent617f73f8a9063c314c15c48d432e36036253bedd (diff)
use accurate log10 for meter (fast_log2 is unsuitable inaccurate)
fast_coefficient_to_dB() returns a lower bound value, unsuitable to catch audio peaks. The difference to 20*log10 is as large as 0.4 dB! The effective speedup of fast_log10 compared to log10f is marginal (sweep of all 24bit values) i686 (1.6GHz Intel core): 2.36 [times faster] x86_64 (core2 2.4GHz): 1.63 x86_64 (I3 2.80GHz): 2.03 the execution time of one log10f() averaged over a sweep of all 24 bit values i686 (1.6GHz Intel core): 0.131 usec x86_64 (core2 2.4GHz): 0.033 usec x86_64 (I3 2.80GHz): 0.044 usec PeakMeter::run() is called from dedicated non-rt, no harm done.
Diffstat (limited to 'libs/ardour/meter.cc')
-rw-r--r--libs/ardour/meter.cc17
1 files changed, 9 insertions, 8 deletions
diff --git a/libs/ardour/meter.cc b/libs/ardour/meter.cc
index 41500c7cb0..f239a1c4b7 100644
--- a/libs/ardour/meter.cc
+++ b/libs/ardour/meter.cc
@@ -55,6 +55,8 @@ PeakMeter::~PeakMeter ()
* Input acceptance is lenient - the first n buffers from @a bufs will
* be metered, where n was set by the last call to setup(), excess meters will
* be set to 0.
+ *
+ * (runs in jack realtime context)
*/
void
PeakMeter::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/, pframes_t nframes, bool)
@@ -95,7 +97,7 @@ PeakMeter::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_fr
// Meter audio in to the rest of the peaks
for (uint32_t i = 0; i < n_audio; ++i, ++n) {
_peak_signal[n] = compute_peak (bufs.get_audio(i).data(), nframes, _peak_signal[n]);
- if (/* TODO use separate bit-flags for mixer,meterbridge,.. */ /* 1 || */ _meter_type & MeterKrms) {
+ if (_meter_type & MeterKrms) {
_kmeter[i]->process(bufs.get_audio(i).data(), nframes);
}
}
@@ -239,11 +241,7 @@ PeakMeter::meter ()
;
} else {
/* empirical WRT to falloff times , 0.01f ^= 100 Hz update rate */
-#if 1
- new_peak = _visible_peak_power[n] - _visible_peak_power[n] * Config->get_meter_falloff() * 0.01f * 0.05f;
-#else
new_peak = _visible_peak_power[n] - sqrt(_visible_peak_power[n] * Config->get_meter_falloff() * 0.01f * 0.0002f);
-#endif
if (new_peak < (1.0 / 512.0)) new_peak = 0;
}
_visible_peak_power[n] = new_peak;
@@ -257,7 +255,7 @@ PeakMeter::meter ()
_max_peak_signal[n] = std::max(new_peak, _max_peak_signal[n]);
if (new_peak > 0.0) {
- new_peak = fast_coefficient_to_dB (new_peak);
+ new_peak = accurate_coefficient_to_dB (new_peak);
} else {
new_peak = minus_infinity();
}
@@ -283,7 +281,11 @@ PeakMeter::meter_level(uint32_t n, MeterType type) {
{
const uint32_t n_midi = current_meters.n_midi();
if ((n - n_midi) < _kmeter.size() && (n - n_midi) >= 0) {
+#if 0
return fast_coefficient_to_dB (_kmeter[n-n_midi]->read());
+#else
+ return accurate_coefficient_to_dB (_kmeter[n-n_midi]->read());
+#endif
}
return minus_infinity();
}
@@ -304,6 +306,7 @@ PeakMeter::meter_level(uint32_t n, MeterType type) {
}
}
}
+
void
PeakMeter::set_type(MeterType t)
{
@@ -329,5 +332,3 @@ PeakMeter::state (bool full_state)
node.add_property("type", "meter");
return node;
}
-
-