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<?xml version="1.0"?>
<!DOCTYPE ladspa SYSTEM "ladspa-swh.dtd">
<?xml-stylesheet href="ladspa.css" type="text/css"?>
<ladspa>
<global>
<meta name="maker" value="Steve Harris <steve@plugin.org.uk>"/>
<meta name="copyright" value="GPL"/>
<meta name="properties" value="HARD_RT_CAPABLE"/>
<code>
#include "ladspa-util.h"
#include "util/db.h"
/* Minimum buffer size in seconds */
#define BUFFER_TIME 0.15f
</code>
</global>
<plugin label="lookaheadLimiterConst" id="1906" class="LimiterPlugin">
<name>Lookahead limiter (fixed latency)</name>
<p>A lookahead limiter - similar to the original Lookahead Limiter, but
with a constant latency of around 150ms and a reduced maximum lookahead
time.</p>
<callback event="instantiate"><![CDATA[
buffer_len = 4096;
buffer_pos = 0;
fs = s_rate;
db_init();
/* Find size for power-of-two interleaved delay buffer */
while(buffer_len < s_rate * BUFFER_TIME) {
buffer_len *= 2;
}
buffer_mask = buffer_len * 2 - 1;
buffer = calloc(buffer_len * 2, sizeof(LADSPA_Data));
amp_buffer = calloc(buffer_len, sizeof(float));
peak = 0.0f;
peak_dist = 1;
atten = 0.0f;
last_delay = -1.0f;
]]></callback>
<callback event="activate"><![CDATA[
int i;
memset(buffer, 0, buffer_len * 2 * sizeof(float));
for (i=0; i<buffer_len; i++) amp_buffer[i] = 1.0f;
buffer_pos = 0;
peak = 0.0f;
peak_dist = 1;
atten = 0.0f;
last_delay = -1.0f;
]]></callback>
<callback event="run"><![CDATA[
unsigned long pos;
const float max = DB_CO(limit);
float sig, gain;
float delay = last_delay;
float delay_delta;
float a, b;
if (delay < 0.0f) {
delay = delay_s * fs;
delay_delta = 0.0f;
} else {
delay_delta = (delay_s * fs - last_delay) / (sample_count - 1);
}
for (pos = 0; pos < sample_count; pos++) {
delay += delay_delta;
buffer[(buffer_pos * 2) & buffer_mask] = in_1[pos];
buffer[(buffer_pos * 2 + 1) & buffer_mask] = in_2[pos];
a = fabs(buffer[((buffer_pos + f_round(delay)) * 2) & buffer_mask]);
b = fabs(buffer[((buffer_pos + f_round(delay)) * 2 + 1) & buffer_mask]);
sig = a > b ? a : b;
/* XXX
sig = fabs(in_1[pos]) > fabs(in_2[pos]) ? fabs(in_1[pos]) :
fabs(in_2[pos]);
*/
if (sig > max) {
const float rel = lin2db(sig) - limit;
if (rel / delay > peak / (float)peak_dist) {
peak_dist = delay;
peak = rel;
}
}
/* Incremenatlly approach the correct attenuation for the next peak */
atten -= (atten - peak) / (float)(peak_dist + 1);
if (peak_dist-- == 0) {
peak_dist = f_round(delay);
peak = 0.0f;
}
/* Cacluate the apropriate gain reduction and write it back into the
* buffer */
gain = amp_buffer[(buffer_pos - f_round(delay)) & (buffer_len - 1)];
amp_buffer[(buffer_pos - f_round(delay)) & (buffer_len - 1)] =
1.0f / db2lin(atten);
gain=1.0f / db2lin(atten);
buffer_write(out_1[pos], buffer[(2 * (buffer_pos + 1)) &
buffer_mask] * gain);
buffer_write(out_2[pos], buffer[(2 * (buffer_pos + 1)+1) &
buffer_mask] * gain);
/* Ensure that the signal really can't be over the limit */
#if 0
XXX FIXME XXX
if (out_1[pos] < -max) {
buffer_write(out_1[pos], -max);
} else if (out_1[pos] > max) {
buffer_write(out_1[pos], max);
}
if (out_2[pos] < -max) {
buffer_write(out_2[pos], -max);
} else if (out_2[pos] > max) {
buffer_write(out_2[pos], max);
}
#endif
buffer_pos++;
}
plugin_data->buffer_pos = buffer_pos;
plugin_data->peak = peak;
plugin_data->peak_dist = peak_dist;
plugin_data->atten = atten;
plugin_data->last_delay = delay;
*(plugin_data->attenuation) = atten;
*(plugin_data->latency) = buffer_len - 1;
]]></callback>
<callback event="cleanup"><![CDATA[
free(plugin_data->buffer);
free(plugin_data->amp_buffer);
]]></callback>
<port label="limit" dir="input" type="control" hint="default_0">
<name>Limit (dB)</name>
<p>The maximum output amplitude. Peaks over this level will be attenuated as smoothly as possible to bring them as close as possible to this level.</p>
<range min="-20" max="0"/>
</port>
<port label="delay_s" dir="input" type="control" hint="default_middle">
<name>Lookahead time (s)</name>
<p>The delay time used by the lookahead predictor. The longer the time the smoother the limiting will be, but will tend to make the changes in dynamic range more obvious.</p>
<range min="0.001" max="0.15"/>
</port>
<port label="attenuation" dir="output" type="control">
<name>Attenuation (dB)</name>
<p>The current limiting attenuation of the signal coming out of the delay
buffer.</p>
<range min="0" max="12"/>
</port>
<port label="in_1" dir="input" type="audio">
<name>Input 1</name>
</port>
<port label="in_2" dir="input" type="audio">
<name>Input 2</name>
</port>
<port label="out_1" dir="output" type="audio">
<name>Output 1</name>
</port>
<port label="out_2" dir="output" type="audio">
<name>Output 2</name>
</port>
<port label="latency" dir="output" type="control">
<name>latency</name>
</port>
<instance-data label="buffer" type="LADSPA_Data *" />
<instance-data label="amp_buffer" type="float *" />
<instance-data label="buffer_len" type="unsigned int" />
<instance-data label="buffer_mask" type="unsigned int" />
<instance-data label="buffer_pos" type="unsigned int" />
<instance-data label="fs" type="unsigned int" />
<!-- running value for the attenuation -->
<instance-data label="atten" type="float" />
<!-- the next peak, relative to the limit -->
<instance-data label="peak" type="float" />
<!-- the number of sample until the next peak -->
<instance-data label="peak_dist" type="unsigned int" />
<instance-data label="last_delay" type="float" />
</plugin>
</ladspa>
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