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Rebake of AM, NFM demodulators -- more flexible filtering/configuration.

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Also make SpectrumCollector dynamically configurable.
Add deemphasis filter to NFM.
This commit is contained in:
Jared Boone
2015-12-29 10:58:53 -08:00
parent df593c2f0f
commit bbfcca8ec0
8 changed files with 249 additions and 64 deletions
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168
firmware/baseband/proc_nfm_audio.cpp
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@@ -24,44 +24,163 @@
#include <cstdint>
#include <cstddef>
// NBFM 16K0F3E emission type /////////////////////////////////////////////
// IFIR image-reject filter: fs=3072000, pass=8000, stop=344000, decim=8, fout=384000
static constexpr std::array<int16_t, 24> taps_16k0_decim_0 { {
1, 67, 165, 340, 599, 944, 1361, 1820,
2278, 2684, 2988, 3152, 3152, 2988, 2684, 2278,
1820, 1361, 944, 599, 340, 165, 67, 1,
} };
// IFIR prototype filter: fs=384000, pass=8000, stop=40000, decim=8, fout=48000
static constexpr std::array<int16_t, 32> taps_16k0_decim_1 { {
-26, -125, -180, -275, -342, -359, -286, -90,
250, 733, 1337, 2011, 2688, 3289, 3740, 3982,
3982, 3740, 3289, 2688, 2011, 1337, 733, 250,
-90, -286, -359, -342, -275, -180, -125, -26,
} };
// Channel filter: fs=48000, pass=8000, stop=12400, decim=1, fout=48000
static constexpr std::array<int16_t, 32> taps_16k0_channel { {
-73, -285, -376, -8, 609, 538, -584, -1387,
-148, 2173, 1959, -2146, -5267, -297, 12915, 24737,
24737, 12915, -297, -5267, -2146, 1959, 2173, -148,
-1387, -584, 538, 609, -8, -376, -285, -73,
} };
// NBFM 11K0F3E emission type /////////////////////////////////////////////
// IFIR image-reject filter: fs=3072000, pass=5500, stop=341500, decim=8, fout=384000
static constexpr std::array<int16_t, 24> taps_11k0_decim_0 { {
38, 102, 220, 406, 668, 1004, 1397, 1822,
2238, 2603, 2875, 3020, 3020, 2875, 2603, 2238,
1822, 1397, 1004, 668, 406, 220, 102, 38,
} };
// IFIR prototype filter: fs=384000, pass=5500, stop=42500, decim=8, fout=48000
static constexpr std::array<int16_t, 32> taps_11k0_decim_1 { {
-42, -87, -157, -234, -298, -318, -255, -75,
246, 713, 1306, 1976, 2656, 3265, 3724, 3971,
3971, 3724, 3265, 2656, 1976, 1306, 713, 246,
-75, -255, -318, -298, -234, -157, -87, -42,
} };
// Channel filter: fs=48000, pass=5500, stop=8900, decim=1, fout=48000
static constexpr std::array<int16_t, 32> taps_11k0_channel { {
-68, -345, -675, -867, -582, 247, 1222, 1562,
634, -1379, -3219, -3068, 310, 6510, 13331, 17795,
17795, 13331, 6510, 310, -3068, -3219, -1379, 634,
1562, 1222, 247, -582, -867, -675, -345, -68,
} };
/// NBFM 8K50F3E emission type ////////////////////////////////////////////
// IFIR image-reject filter: fs=3072000, pass=4250, stop=340250, decim=8, fout=384000
static constexpr std::array<int16_t, 24> taps_4k25_decim_0 { {
38, 103, 222, 409, 671, 1006, 1399, 1821,
2236, 2599, 2868, 3012, 3012, 2868, 2599, 2236,
1821, 1399, 1006, 671, 409, 222, 103, 38,
} };
// IFIR prototype filter: fs=384000, pass=4250, stop=43750, decim=8, fout=48000
static constexpr std::array<int16_t, 32> taps_4k25_decim_1 { {
-33, -74, -139, -214, -280, -306, -254, -87,
222, 682, 1274, 1951, 2644, 3268, 3741, 3996,
3996, 3741, 3268, 2644, 1951, 1274, 682, 222,
-87, -254, -306, -280, -214, -139, -74, -33,
} };
// Channel filter: fs=48000, pass=4250, stop=7900, decim=1, fout=48000
static constexpr std::array<int16_t, 32> taps_4k25_channel { {
-58, -14, 153, 484, 871, 1063, 770, -141,
-1440, -2488, -2435, -614, 3035, 7771, 12226, 14927,
14927, 12226, 7771, 3035, -614, -2435, -2488, -1440,
-141, 770, 1063, 871, 484, 153, -14, -58,
} };
NarrowbandFMAudio::NarrowbandFMAudio() {
set_mode(Mode::Deviation2K5Narrow);
}
void NarrowbandFMAudio::set_mode(const Mode mode) {
constexpr size_t baseband_fs = 3072000;
constexpr size_t decim_0_input_fs = baseband_fs;
constexpr size_t decim_0_decimation_factor = 8;
constexpr size_t decim_0_output_fs = decim_0_input_fs / decim_0_decimation_factor;
constexpr size_t decim_1_input_fs = decim_0_output_fs;
constexpr size_t decim_1_decimation_factor = 8;
constexpr size_t decim_1_output_fs = decim_1_input_fs / decim_1_decimation_factor;
constexpr size_t channel_filter_input_fs = decim_1_output_fs;
constexpr size_t channel_filter_decimation_factor = 1;
constexpr size_t channel_filter_output_fs = channel_filter_input_fs / channel_filter_decimation_factor;
constexpr size_t demod_input_fs = channel_filter_output_fs;
switch(mode) {
default:
case Mode::Deviation5K:
decim_0.configure(taps_16k0_decim_0, 33554432);
decim_1.configure(taps_16k0_decim_1, 131072);
channel_filter.configure(taps_16k0_channel, channel_filter_decimation_factor);
demod.configure(demod_input_fs, 5000);
channel_filter_pass_f = 8000;
channel_filter_stop_f = 12400;
break;
case Mode::Deviation2K5Wide:
decim_0.configure(taps_11k0_decim_0, 33554432);
decim_1.configure(taps_11k0_decim_1, 131072);
channel_filter.configure(taps_11k0_channel, channel_filter_decimation_factor);
demod.configure(demod_input_fs, 2500);
channel_filter_pass_f = 5500;
channel_filter_stop_f = 8900;
break;
case Mode::Deviation2K5Narrow:
decim_0.configure(taps_4k25_decim_0, 33554432);
decim_1.configure(taps_4k25_decim_1, 131072);
channel_filter.configure(taps_4k25_channel, channel_filter_decimation_factor);
demod.configure(demod_input_fs, 2500);
channel_filter_pass_f = 4250;
channel_filter_stop_f = 7900;
break;
}
channel_spectrum.set_decimation_factor(std::floor((channel_filter_output_fs / 2) / ((channel_filter_pass_f + channel_filter_stop_f) / 2)));
}
void NarrowbandFMAudio::execute(const buffer_c8_t& buffer) {
/* Called every 2048/3072000 second -- 1500Hz. */
auto decimator_out = decimator.execute(buffer);
const buffer_c16_t work_baseband_buffer {
(complex16_t*)decimator_out.p,
sizeof(*decimator_out.p) * decimator_out.count
const buffer_c16_t dst_buffer {
dst.data(),
dst.size()
};
/* 96kHz complex<int16_t>[64]
* -> FIR filter, <6kHz (0.063fs) pass, gain 1.0
* -> 48kHz int16_t[32] */
auto channel = channel_filter.execute(decimator_out, work_baseband_buffer);
const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
const auto channel_out = channel_filter.execute(decim_1_out, dst_buffer);
// TODO: Feed channel_stats post-decimation data?
feed_channel_stats(channel);
channel_spectrum.feed(
channel,
decimator_out.sampling_rate * channel_filter_taps.pass_frequency_normalized,
decimator_out.sampling_rate * channel_filter_taps.stop_frequency_normalized
);
feed_channel_stats(channel_out);
channel_spectrum.feed(channel_out, channel_filter_pass_f, channel_filter_stop_f);
const buffer_s16_t work_audio_buffer {
(int16_t*)decimator_out.p,
sizeof(*decimator_out.p) * decimator_out.count
(int16_t*)dst.data(),
sizeof(*dst.data()) * dst.size()
};
/* 48kHz complex<int16_t>[32]
* -> FM demodulation
* -> 48kHz int16_t[32] */
auto audio = demod.execute(channel, work_audio_buffer);
auto audio = demod.execute(channel_out, work_audio_buffer);
static uint64_t audio_present_history = 0;
const auto audio_present_now = squelch.execute(audio);
audio_present_history = (audio_present_history << 1) | (audio_present_now ? 1 : 0);
const bool audio_present = (audio_present_history != 0);
audio_hpf.execute_in_place(audio);
audio_deemph.execute_in_place(audio);
if( !audio_present ) {
// Zero audio buffer.
for(size_t i=0; i<audio.count; i++) {
@@ -69,6 +188,5 @@ void NarrowbandFMAudio::execute(const buffer_c8_t& buffer) {
}
}
audio_hpf.execute_in_place(audio);
fill_audio_buffer(audio);
}