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Reduce LIMITER_VALUE_MAX

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The previous value couldn't actually be expressed as a float and got rounded up
to the next whole number value, leaving the potential for an overrun in the
squared sum.
This commit is contained in:
Chris Robinson
2017-05-09 11:50:25 -07:00
parent 4a4442ad91
commit a2c25378a9
2 changed files with 13 additions and 7 deletions
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Alc/ALu.c
+12 -6
View File
@@ -1427,6 +1427,8 @@ static void UpdateContextSources(ALCcontext *ctx, const struct ALeffectslotArray
}
static_assert(LIMITER_VALUE_MAX < (UINT_MAX/LIMITER_WINDOW_SIZE), "LIMITER_VALUE_MAX is too big");
static void ApplyLimiter(struct OutputLimiter *Limiter,
ALfloat (*restrict OutBuffer)[BUFFERSIZE], const ALsizei NumChans,
const ALfloat AttackRate, const ALfloat ReleaseRate,
@@ -1446,8 +1448,8 @@ static void ApplyLimiter(struct OutputLimiter *Limiter,
{
for(i = 0;i < SamplesToDo;i++)
{
ALfloat amp_sqr = OutBuffer[c][i] * OutBuffer[c][i];
Values[i] = maxf(Values[i], amp_sqr);
ALfloat amp = OutBuffer[c][i];
Values[i] = maxf(Values[i], amp*amp);
}
}
@@ -1456,7 +1458,7 @@ static void ApplyLimiter(struct OutputLimiter *Limiter,
ALfloat lastgain = Limiter->Gain;
ALsizei wpos = Limiter->Pos;
ALuint sum = Limiter->SquaredSum;
ALfloat gain;
ALfloat gain, rms;
for(i = 0;i < SamplesToDo;i++)
{
@@ -1464,9 +1466,13 @@ static void ApplyLimiter(struct OutputLimiter *Limiter,
Limiter->Window[wpos] = fastf2u(minf(Values[i]*65536.0f, LIMITER_VALUE_MAX));
sum += Limiter->Window[wpos];
/* Clamp limiter range to 0dB...-80dB. */
gain = 1.0f / clampf(sqrtf((ALfloat)sum / ((ALfloat)LIMITER_WINDOW_SIZE*65536.0f)),
1.0f, 1000.0f);
rms = sqrtf((ALfloat)sum / ((ALfloat)LIMITER_WINDOW_SIZE*65536.0f));
/* Clamp the minimum RMS to 0dB. The uint used for the squared sum
* inherently limits the maximum RMS to about 21dB, thus the gain
* ranges from 0dB to -21dB.
*/
gain = 1.0f / maxf(rms, 1.0f);
if(lastgain >= gain)
lastgain = maxf(lastgain*AttackRate, gain);
else
OpenAL32/Include/alu.h
+1 -1
View File
@@ -299,7 +299,7 @@ void DeinitVoice(ALvoice *voice);
#define LIMITER_WINDOW_SIZE (1<<7) /* 128 */
#define LIMITER_WINDOW_MASK (LIMITER_WINDOW_SIZE-1)
#define LIMITER_VALUE_MAX (UINT_MAX / LIMITER_WINDOW_SIZE)
#define LIMITER_VALUE_MAX (1<<24) /* 16777216 */
struct OutputLimiter {
/* RMS detection window, sum of values in the window, and the next write
* pos. Values are 16.16 fixed-point.