diff options
Diffstat (limited to 'servers/audio')
| -rw-r--r-- | servers/audio/audio_stream.cpp | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/servers/audio/audio_stream.cpp b/servers/audio/audio_stream.cpp index 91fce5d34e..dfd54adcd8 100644 --- a/servers/audio/audio_stream.cpp +++ b/servers/audio/audio_stream.cpp @@ -54,21 +54,21 @@ void AudioStreamPlaybackResampled::mix(AudioFrame *p_buffer, float p_rate_scale, for (int i = 0; i < p_frames; i++) { uint32_t idx = CUBIC_INTERP_HISTORY + uint32_t(mix_offset >> FP_BITS); - //standard cubic interpolation (great quality/performance ratio) - //this used to be moved to a LUT for greater performance, but nowadays CPU speed is generally faster than memory. + // 4 point, 4th order optimal resampling algorithm from: http://yehar.com/blog/wp-content/uploads/2009/08/deip.pdf float mu = (mix_offset & FP_MASK) / float(FP_LEN); AudioFrame y0 = internal_buffer[idx - 3]; AudioFrame y1 = internal_buffer[idx - 2]; AudioFrame y2 = internal_buffer[idx - 1]; AudioFrame y3 = internal_buffer[idx - 0]; - float mu2 = mu * mu; - AudioFrame a0 = y3 - y2 - y0 + y1; - AudioFrame a1 = y0 - y1 - a0; - AudioFrame a2 = y2 - y0; - AudioFrame a3 = y1; - - p_buffer[i] = (a0 * mu * mu2 + a1 * mu2 + a2 * mu + a3); + AudioFrame even1 = y2 + y1, odd1 = y2 - y1; + AudioFrame even2 = y3 + y0, odd2 = y3 - y0; + AudioFrame c0 = even1 * 0.46835497211269561 + even2 * 0.03164502784253309; + AudioFrame c1 = odd1 * 0.56001293337091440 + odd2 * 0.14666238593949288; + AudioFrame c2 = even1 * -0.250038759826233691 + even2 * 0.25003876124297131; + AudioFrame c3 = odd1 * -0.49949850957839148 + odd2 * 0.16649935475113800; + AudioFrame c4 = even1 * 0.00016095224137360 + even2 * -0.00016095810460478; + p_buffer[i] = (((c4 * mu + c3) * mu + c2) * mu + c1) * mu + c0; mix_offset += mix_increment; |