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Changes audio module decimation filter from lowpass to bandpass so that we can remove 0-250 Hz and any LTR signalling from the audio output.

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Denny
2016-08-21 07:21:38 -04:00
parent 3af4b953f4
commit d466ec9f5e
5 changed files with 745 additions and 735 deletions
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24
src/audio/AudioModule.java
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@@ -46,15 +46,15 @@ public class AudioModule extends Module implements IAudioPacketProvider,
static
{
FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
.sampleRate(48000)
.gridDensity(16)
.passBandCutoff(3000)
.passBandAmplitude(1.0)
.passBandRipple(0.01)
.stopBandStart(4000)
.stopBandAmplitude(0.0)
.stopBandRipple(0.027)
//Band-pass filter to both decimate (48kHz to 8kHz) and block 0 - 300 Hz (LTR signalling).
FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
.sampleRate( 48000 )
.stopFrequency1( 150 )
.passFrequencyBegin( 300 )
.passFrequencyEnd( 3500 )
.stopFrequency2( 4000 )
.stopRipple( 0.0004 )
.passRipple( 0.008)
.build();
RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
@@ -86,16 +86,12 @@ public class AudioModule extends Module implements IAudioPacketProvider,
private Listener<AudioPacket> mAudioPacketListener;
private PolyphaseFIRDecimatingFilter_RB mAudioDecimationFilter;
//TODO: remove this -- is being replaced by the DemodulatedAudioFilterModule
private RealFIRFilter_R_R mAudioFilter = new RealFIRFilter_R_R(
Filters.FIR_BANDPASS_AUDIO_48KHZ.getCoefficients(), 2.0f);
public AudioModule(boolean record)
{
mSourceID = ++UNIQUE_ID;
mAudioMetadata = new AudioMetadata(mSourceID, record);
mAudioDecimationFilter = new PolyphaseFIRDecimatingFilter_RB(mDecimationCoefficients, 6);
mAudioDecimationFilter = new PolyphaseFIRDecimatingFilter_RB(mDecimationCoefficients, 6, 2.0f);
mAudioDecimationFilter.setListener(new Listener<RealBuffer>()
{
@Override