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Increase filter order for baseband downsample filter. Add comments.

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Joris van Rantwijk 2013-12-30 15:58:17 +01:00
parent 48d605243b
commit 620dba5d13
1 changed files with 20 additions and 4 deletions
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24
FmDecode.cc
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@ -216,6 +216,8 @@ FmDecoder::FmDecoder(double sample_rate_if,
double freq_dev, double freq_dev,
double bandwidth_pcm, double bandwidth_pcm,
unsigned int downsample) unsigned int downsample)
// Initialize member fields
: m_sample_rate_if(sample_rate_if) : m_sample_rate_if(sample_rate_if)
, m_tuning_table_size(64) , m_tuning_table_size(64)
, m_tuning_shift(lrint(-64.0 * tuning_offset / sample_rate_if)) , m_tuning_shift(lrint(-64.0 * tuning_offset / sample_rate_if))
@ -226,18 +228,32 @@ FmDecoder::FmDecoder(double sample_rate_if,
, m_if_level(0) , m_if_level(0)
, m_baseband_mean(0) , m_baseband_mean(0)
, m_baseband_level(0) , m_baseband_level(0)
// Construct FineTuner
, m_finetuner(m_tuning_table_size, m_tuning_shift) , m_finetuner(m_tuning_table_size, m_tuning_shift)
// Construct LowPassFilterFirIQ
, m_iffilter(10, bandwidth_if / sample_rate_if) , m_iffilter(10, bandwidth_if / sample_rate_if)
// Construct PhaseDiscriminator
, m_phasedisc(freq_dev / sample_rate_if) , m_phasedisc(freq_dev / sample_rate_if)
, m_resample_baseband(6 * downsample,
0.5 / downsample, // Construct DownsampleFilter for baseband
downsample, true) , m_resample_baseband(8 * downsample, 0.4 / downsample, downsample, true)
, m_resample_mono(int(15 * sample_rate_if / downsample / bandwidth_pcm),
// Construct DownsampleFilter for mono channel
, m_resample_mono(int(sample_rate_if / downsample / 1000.0),
bandwidth_pcm * downsample / sample_rate_if, bandwidth_pcm * downsample / sample_rate_if,
sample_rate_if / downsample / sample_rate_pcm, false) sample_rate_if / downsample / sample_rate_pcm, false)
// Construct HighPassFilterIir
, m_dcblock_mono(30.0 / sample_rate_pcm) , m_dcblock_mono(30.0 / sample_rate_pcm)
// Construct LowwPassFilterRC
, m_deemph_mono((deemphasis == 0) ? 1.0 : (deemphasis * sample_rate_pcm * 1.0e-6)) , m_deemph_mono((deemphasis == 0) ? 1.0 : (deemphasis * sample_rate_pcm * 1.0e-6))
{ {
// nothing more to do
} }