]> git.sesse.net Git - nageru/blobdiff - audio_mixer.cpp
Write 1.4.0 changelog.
[nageru] / audio_mixer.cpp
index c4f6f0b52c9f055414f5d06542502727aeec2de1..e4d4cff4b86222e41d6b0d8181b8d519a1f1b6a1 100644 (file)
@@ -1,18 +1,31 @@
 #include "audio_mixer.h"
 
 #include <assert.h>
-#include <endian.h>
 #include <bmusb/bmusb.h>
-#include <stdio.h>
 #include <endian.h>
+#include <math.h>
+#ifdef __SSE2__
+#include <immintrin.h>
+#endif
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <algorithm>
+#include <chrono>
 #include <cmath>
+#include <cstddef>
+#include <limits>
+#include <utility>
 
 #include "db.h"
 #include "flags.h"
+#include "state.pb.h"
 #include "timebase.h"
 
 using namespace bmusb;
 using namespace std;
+using namespace std::placeholders;
 
 namespace {
 
@@ -76,45 +89,139 @@ void convert_fixed32_to_fp32(float *dst, size_t out_channel, size_t out_num_chan
        }
 }
 
+float find_peak_plain(const float *samples, size_t num_samples) __attribute__((unused));
+
+float find_peak_plain(const float *samples, size_t num_samples)
+{
+       float m = fabs(samples[0]);
+       for (size_t i = 1; i < num_samples; ++i) {
+               m = max(m, fabs(samples[i]));
+       }
+       return m;
+}
+
+#ifdef __SSE__
+static inline float horizontal_max(__m128 m)
+{
+       __m128 tmp = _mm_shuffle_ps(m, m, _MM_SHUFFLE(1, 0, 3, 2));
+       m = _mm_max_ps(m, tmp);
+       tmp = _mm_shuffle_ps(m, m, _MM_SHUFFLE(2, 3, 0, 1));
+       m = _mm_max_ps(m, tmp);
+       return _mm_cvtss_f32(m);
+}
+
+float find_peak(const float *samples, size_t num_samples)
+{
+       const __m128 abs_mask = _mm_castsi128_ps(_mm_set1_epi32(0x7fffffffu));
+       __m128 m = _mm_setzero_ps();
+       for (size_t i = 0; i < (num_samples & ~3); i += 4) {
+               __m128 x = _mm_loadu_ps(samples + i);
+               x = _mm_and_ps(x, abs_mask);
+               m = _mm_max_ps(m, x);
+       }
+       float result = horizontal_max(m);
+
+       for (size_t i = (num_samples & ~3); i < num_samples; ++i) {
+               result = max(result, fabs(samples[i]));
+       }
+
+#if 0
+       // Self-test. We should be bit-exact the same.
+       float reference_result = find_peak_plain(samples, num_samples);
+       if (result != reference_result) {
+               fprintf(stderr, "Error: Peak is %f [%f %f %f %f]; should be %f.\n",
+                       result,
+                       _mm_cvtss_f32(_mm_shuffle_ps(m, m, _MM_SHUFFLE(0, 0, 0, 0))),
+                       _mm_cvtss_f32(_mm_shuffle_ps(m, m, _MM_SHUFFLE(1, 1, 1, 1))),
+                       _mm_cvtss_f32(_mm_shuffle_ps(m, m, _MM_SHUFFLE(2, 2, 2, 2))),
+                       _mm_cvtss_f32(_mm_shuffle_ps(m, m, _MM_SHUFFLE(3, 3, 3, 3))),
+                       reference_result);
+               abort();
+       }
+#endif
+       return result;
+}
+#else
+float find_peak(const float *samples, size_t num_samples)
+{
+       return find_peak_plain(samples, num_samples);
+}
+#endif
+
+void deinterleave_samples(const vector<float> &in, vector<float> *out_l, vector<float> *out_r)
+{
+       size_t num_samples = in.size() / 2;
+       out_l->resize(num_samples);
+       out_r->resize(num_samples);
+
+       const float *inptr = in.data();
+       float *lptr = &(*out_l)[0];
+       float *rptr = &(*out_r)[0];
+       for (size_t i = 0; i < num_samples; ++i) {
+               *lptr++ = *inptr++;
+               *rptr++ = *inptr++;
+       }
+}
+
 }  // namespace
 
 AudioMixer::AudioMixer(unsigned num_cards)
        : num_cards(num_cards),
-         level_compressor(OUTPUT_FREQUENCY),
          limiter(OUTPUT_FREQUENCY),
-         compressor(OUTPUT_FREQUENCY)
+         correlation(OUTPUT_FREQUENCY)
 {
-       locut.init(FILTER_HPF, 2);
+       global_audio_mixer = this;
 
-       set_locut_enabled(global_flags.locut_enabled);
-       set_gain_staging_db(global_flags.initial_gain_staging_db);
-       set_gain_staging_auto(global_flags.gain_staging_auto);
-       set_compressor_enabled(global_flags.compressor_enabled);
+       for (unsigned bus_index = 0; bus_index < MAX_BUSES; ++bus_index) {
+               locut[bus_index].init(FILTER_HPF, 2);
+               eq[bus_index][EQ_BAND_BASS].init(FILTER_LOW_SHELF, 1);
+               // Note: EQ_BAND_MID isn't used (see comments in apply_eq()).
+               eq[bus_index][EQ_BAND_TREBLE].init(FILTER_HIGH_SHELF, 1);
+               compressor[bus_index].reset(new StereoCompressor(OUTPUT_FREQUENCY));
+               level_compressor[bus_index].reset(new StereoCompressor(OUTPUT_FREQUENCY));
+
+               set_bus_settings(bus_index, get_default_bus_settings());
+       }
        set_limiter_enabled(global_flags.limiter_enabled);
        set_final_makeup_gain_auto(global_flags.final_makeup_gain_auto);
+       alsa_pool.init();
+
+       if (!global_flags.input_mapping_filename.empty()) {
+               current_mapping_mode = MappingMode::MULTICHANNEL;
+               InputMapping new_input_mapping;
+               if (!load_input_mapping_from_file(get_devices(),
+                                                 global_flags.input_mapping_filename,
+                                                 &new_input_mapping)) {
+                       fprintf(stderr, "Failed to load input mapping from '%s', exiting.\n",
+                               global_flags.input_mapping_filename.c_str());
+                       exit(1);
+               }
+               set_input_mapping(new_input_mapping);
+       } else {
+               set_simple_input(/*card_index=*/0);
+               if (global_flags.multichannel_mapping_mode) {
+                       current_mapping_mode = MappingMode::MULTICHANNEL;
+               }
+       }
 
-       // Generate a very simple, default input mapping.
-       InputMapping::Bus input;
-       input.name = "Main";
-       input.device.type = InputSourceType::CAPTURE_CARD;
-       input.device.index = 0;
-       input.source_channel[0] = 0;
-       input.source_channel[1] = 1;
+       r128.init(2, OUTPUT_FREQUENCY);
+       r128.integr_start();
 
-       InputMapping new_input_mapping;
-       new_input_mapping.buses.push_back(input);
-       set_input_mapping(new_input_mapping);
+       // hlen=16 is pretty low quality, but we use quite a bit of CPU otherwise,
+       // and there's a limit to how important the peak meter is.
+       peak_resampler.setup(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY * 4, /*num_channels=*/2, /*hlen=*/16, /*frel=*/1.0);
 }
 
-void AudioMixer::reset_device(DeviceSpec device_spec)
+void AudioMixer::reset_resampler(DeviceSpec device_spec)
 {
-       lock_guard<mutex> lock(audio_mutex);
-       reset_device_mutex_held(device_spec);
+       lock_guard<timed_mutex> lock(audio_mutex);
+       reset_resampler_mutex_held(device_spec);
 }
 
-void AudioMixer::reset_device_mutex_held(DeviceSpec device_spec)
+void AudioMixer::reset_resampler_mutex_held(DeviceSpec device_spec)
 {
        AudioDevice *device = find_audio_device(device_spec);
+
        if (device->interesting_channels.empty()) {
                device->resampling_queue.reset();
        } else {
@@ -125,22 +232,24 @@ void AudioMixer::reset_device_mutex_held(DeviceSpec device_spec)
        device->next_local_pts = 0;
 }
 
-void AudioMixer::add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned num_samples, AudioFormat audio_format, int64_t frame_length)
+bool AudioMixer::add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned num_samples, AudioFormat audio_format, int64_t frame_length)
 {
        AudioDevice *device = find_audio_device(device_spec);
 
-       lock_guard<mutex> lock(audio_mutex);
+       unique_lock<timed_mutex> lock(audio_mutex, defer_lock);
+       if (!lock.try_lock_for(chrono::milliseconds(10))) {
+               return false;
+       }
        if (device->resampling_queue == nullptr) {
                // No buses use this device; throw it away.
-               return;
+               return true;
        }
 
        unsigned num_channels = device->interesting_channels.size();
        assert(num_channels > 0);
 
        // Convert the audio to fp32.
-       vector<float> audio;
-       audio.resize(num_samples * num_channels);
+       unique_ptr<float[]> audio(new float[num_samples * num_channels]);
        unsigned channel_index = 0;
        for (auto channel_it = device->interesting_channels.cbegin(); channel_it != device->interesting_channels.end(); ++channel_it, ++channel_index) {
                switch (audio_format.bits_per_sample) {
@@ -148,13 +257,13 @@ void AudioMixer::add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned
                        assert(num_samples == 0);
                        break;
                case 16:
-                       convert_fixed16_to_fp32(&audio[0], channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
+                       convert_fixed16_to_fp32(audio.get(), channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
                        break;
                case 24:
-                       convert_fixed24_to_fp32(&audio[0], channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
+                       convert_fixed24_to_fp32(audio.get(), channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
                        break;
                case 32:
-                       convert_fixed32_to_fp32(&audio[0], channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
+                       convert_fixed32_to_fp32(audio.get(), channel_index, num_channels, data, *channel_it, audio_format.num_channels, num_samples);
                        break;
                default:
                        fprintf(stderr, "Cannot handle audio with %u bits per sample\n", audio_format.bits_per_sample);
@@ -164,18 +273,22 @@ void AudioMixer::add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned
 
        // Now add it.
        int64_t local_pts = device->next_local_pts;
-       device->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), audio.data(), num_samples);
+       device->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), audio.get(), num_samples);
        device->next_local_pts = local_pts + frame_length;
+       return true;
 }
 
-void AudioMixer::add_silence(DeviceSpec device_spec, unsigned samples_per_frame, unsigned num_frames, int64_t frame_length)
+bool AudioMixer::add_silence(DeviceSpec device_spec, unsigned samples_per_frame, unsigned num_frames, int64_t frame_length)
 {
        AudioDevice *device = find_audio_device(device_spec);
 
-       lock_guard<mutex> lock(audio_mutex);
+       unique_lock<timed_mutex> lock(audio_mutex, defer_lock);
+       if (!lock.try_lock_for(chrono::milliseconds(10))) {
+               return false;
+       }
        if (device->resampling_queue == nullptr) {
                // No buses use this device; throw it away.
-               return;
+               return true;
        }
 
        unsigned num_channels = device->interesting_channels.size();
@@ -189,6 +302,72 @@ void AudioMixer::add_silence(DeviceSpec device_spec, unsigned samples_per_frame,
                // is always the same.
                device->next_local_pts += frame_length;
        }
+       return true;
+}
+
+bool AudioMixer::silence_card(DeviceSpec device_spec, bool silence)
+{
+       AudioDevice *device = find_audio_device(device_spec);
+
+       unique_lock<timed_mutex> lock(audio_mutex, defer_lock);
+       if (!lock.try_lock_for(chrono::milliseconds(10))) {
+               return false;
+       }
+
+       if (device->silenced && !silence) {
+               reset_resampler_mutex_held(device_spec);
+       }
+       device->silenced = silence;
+       return true;
+}
+
+AudioMixer::BusSettings AudioMixer::get_default_bus_settings()
+{
+       BusSettings settings;
+       settings.fader_volume_db = 0.0f;
+       settings.muted = false;
+       settings.locut_enabled = global_flags.locut_enabled;
+       for (unsigned band_index = 0; band_index < NUM_EQ_BANDS; ++band_index) {
+               settings.eq_level_db[band_index] = 0.0f;
+       }
+       settings.gain_staging_db = global_flags.initial_gain_staging_db;
+       settings.level_compressor_enabled = global_flags.gain_staging_auto;
+       settings.compressor_threshold_dbfs = ref_level_dbfs - 12.0f;  // -12 dB.
+       settings.compressor_enabled = global_flags.compressor_enabled;
+       return settings;
+}
+
+AudioMixer::BusSettings AudioMixer::get_bus_settings(unsigned bus_index) const
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       BusSettings settings;
+       settings.fader_volume_db = fader_volume_db[bus_index];
+       settings.muted = mute[bus_index];
+       settings.locut_enabled = locut_enabled[bus_index];
+       for (unsigned band_index = 0; band_index < NUM_EQ_BANDS; ++band_index) {
+               settings.eq_level_db[band_index] = eq_level_db[bus_index][band_index];
+       }
+       settings.gain_staging_db = gain_staging_db[bus_index];
+       settings.level_compressor_enabled = level_compressor_enabled[bus_index];
+       settings.compressor_threshold_dbfs = compressor_threshold_dbfs[bus_index];
+       settings.compressor_enabled = compressor_enabled[bus_index];
+       return settings;
+}
+
+void AudioMixer::set_bus_settings(unsigned bus_index, const AudioMixer::BusSettings &settings)
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       fader_volume_db[bus_index] = settings.fader_volume_db;
+       mute[bus_index] = settings.muted;
+       locut_enabled[bus_index] = settings.locut_enabled;
+       for (unsigned band_index = 0; band_index < NUM_EQ_BANDS; ++band_index) {
+               eq_level_db[bus_index][band_index] = settings.eq_level_db[band_index];
+       }
+       gain_staging_db[bus_index] = settings.gain_staging_db;
+       last_gain_staging_db[bus_index] = gain_staging_db[bus_index];
+       level_compressor_enabled[bus_index] = settings.level_compressor_enabled;
+       compressor_threshold_dbfs[bus_index] = settings.compressor_threshold_dbfs;
+       compressor_enabled[bus_index] = settings.compressor_enabled;
 }
 
 AudioMixer::AudioDevice *AudioMixer::find_audio_device(DeviceSpec device)
@@ -196,6 +375,8 @@ AudioMixer::AudioDevice *AudioMixer::find_audio_device(DeviceSpec device)
        switch (device.type) {
        case InputSourceType::CAPTURE_CARD:
                return &video_cards[device.index];
+       case InputSourceType::ALSA_INPUT:
+               return &alsa_inputs[device.index];
        case InputSourceType::SILENCE:
        default:
                assert(false);
@@ -203,7 +384,9 @@ AudioMixer::AudioDevice *AudioMixer::find_audio_device(DeviceSpec device)
        return nullptr;
 }
 
-void AudioMixer::find_sample_src_from_device(const vector<float> *samples_card, DeviceSpec device_spec, int source_channel, const float **srcptr, unsigned *stride)
+// Get a pointer to the given channel from the given device.
+// The channel must be picked out earlier and resampled.
+void AudioMixer::find_sample_src_from_device(const map<DeviceSpec, vector<float>> &samples_card, DeviceSpec device_spec, int source_channel, const float **srcptr, unsigned *stride)
 {
        static float zero = 0.0f;
        if (source_channel == -1 || device_spec.type == InputSourceType::SILENCE) {
@@ -212,23 +395,27 @@ void AudioMixer::find_sample_src_from_device(const vector<float> *samples_card,
                return;
        }
        AudioDevice *device = find_audio_device(device_spec);
+       assert(device->interesting_channels.count(source_channel) != 0);
        unsigned channel_index = 0;
        for (int channel : device->interesting_channels) {
                if (channel == source_channel) break;
                ++channel_index;
        }
        assert(channel_index < device->interesting_channels.size());
-       *srcptr = &samples_card[device_spec.index][channel_index];
+       const auto it = samples_card.find(device_spec);
+       assert(it != samples_card.end());
+       *srcptr = &(it->second)[channel_index];
        *stride = device->interesting_channels.size();
 }
 
 // TODO: Can be SSSE3-optimized if need be.
-void AudioMixer::fill_audio_bus(const vector<float> *samples_card, const InputMapping::Bus &bus, unsigned num_samples, float *output)
+void AudioMixer::fill_audio_bus(const map<DeviceSpec, vector<float>> &samples_card, const InputMapping::Bus &bus, unsigned num_samples, float *output)
 {
        if (bus.device.type == InputSourceType::SILENCE) {
-               memset(output, 0, num_samples * sizeof(*output));
+               memset(output, 0, num_samples * 2 * sizeof(*output));
        } else {
-               assert(bus.device.type == InputSourceType::CAPTURE_CARD);
+               assert(bus.device.type == InputSourceType::CAPTURE_CARD ||
+                      bus.device.type == InputSourceType::ALSA_INPUT);
                const float *lsrc, *rsrc;
                unsigned lstride, rstride;
                float *dptr = output;
@@ -243,102 +430,129 @@ void AudioMixer::fill_audio_bus(const vector<float> *samples_card, const InputMa
        }
 }
 
+vector<DeviceSpec> AudioMixer::get_active_devices() const
+{
+       vector<DeviceSpec> ret;
+       for (unsigned card_index = 0; card_index < MAX_VIDEO_CARDS; ++card_index) {
+               const DeviceSpec device_spec{InputSourceType::CAPTURE_CARD, card_index};
+               if (!find_audio_device(device_spec)->interesting_channels.empty()) {
+                       ret.push_back(device_spec);
+               }
+       }
+       for (unsigned card_index = 0; card_index < MAX_ALSA_CARDS; ++card_index) {
+               const DeviceSpec device_spec{InputSourceType::ALSA_INPUT, card_index};
+               if (!find_audio_device(device_spec)->interesting_channels.empty()) {
+                       ret.push_back(device_spec);
+               }
+       }
+       return ret;
+}
+
+namespace {
+
+void apply_gain(float db, float last_db, vector<float> *samples)
+{
+       if (fabs(db - last_db) < 1e-3) {
+               // Constant over this frame.
+               const float gain = from_db(db);
+               for (size_t i = 0; i < samples->size(); ++i) {
+                       (*samples)[i] *= gain;
+               }
+       } else {
+               // We need to do a fade.
+               unsigned num_samples = samples->size() / 2;
+               float gain = from_db(last_db);
+               const float gain_inc = pow(from_db(db - last_db), 1.0 / num_samples);
+               for (size_t i = 0; i < num_samples; ++i) {
+                       (*samples)[i * 2 + 0] *= gain;
+                       (*samples)[i * 2 + 1] *= gain;
+                       gain *= gain_inc;
+               }
+       }
+}
+
+}  // namespace
+
 vector<float> AudioMixer::get_output(double pts, unsigned num_samples, ResamplingQueue::RateAdjustmentPolicy rate_adjustment_policy)
 {
-       vector<float> samples_card[MAX_VIDEO_CARDS];  // TODO: Needs room for other kinds of capture cards.
+       map<DeviceSpec, vector<float>> samples_card;
        vector<float> samples_bus;
 
-       lock_guard<mutex> lock(audio_mutex);
+       lock_guard<timed_mutex> lock(audio_mutex);
 
        // Pick out all the interesting channels from all the cards.
-       // TODO: If the card has been hotswapped, the number of channels
-       // might have changed; if so, we need to do some sort of remapping
-       // to silence.
-       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
-               AudioDevice *device = &video_cards[card_index];
-               if (!device->interesting_channels.empty()) {
-                       samples_card[card_index].resize(num_samples * device->interesting_channels.size());
+       for (const DeviceSpec &device_spec : get_active_devices()) {
+               AudioDevice *device = find_audio_device(device_spec);
+               samples_card[device_spec].resize(num_samples * device->interesting_channels.size());
+               if (device->silenced) {
+                       memset(&samples_card[device_spec][0], 0, samples_card[device_spec].size() * sizeof(float));
+               } else {
                        device->resampling_queue->get_output_samples(
                                pts,
-                               &samples_card[card_index][0],
+                               &samples_card[device_spec][0],
                                num_samples,
                                rate_adjustment_policy);
                }
        }
 
-       // TODO: Move lo-cut etc. into each bus.
-       vector<float> samples_out;
+       vector<float> samples_out, left, right;
        samples_out.resize(num_samples * 2);
        samples_bus.resize(num_samples * 2);
        for (unsigned bus_index = 0; bus_index < input_mapping.buses.size(); ++bus_index) {
                fill_audio_bus(samples_card, input_mapping.buses[bus_index], num_samples, &samples_bus[0]);
+               apply_eq(bus_index, &samples_bus);
 
-               float volume = from_db(fader_volume_db[bus_index]);
-               if (bus_index == 0) {
-                       for (unsigned i = 0; i < num_samples * 2; ++i) {
-                               samples_out[i] = samples_bus[i] * volume;
-                       }
-               } else {
-                       for (unsigned i = 0; i < num_samples * 2; ++i) {
-                               samples_out[i] += samples_bus[i] * volume;
-                       }
-               }
-       }
-
-       // Cut away everything under 120 Hz (or whatever the cutoff is);
-       // we don't need it for voice, and it will reduce headroom
-       // and confuse the compressor. (In particular, any hums at 50 or 60 Hz
-       // should be dampened.)
-       if (locut_enabled) {
-               locut.render(samples_out.data(), samples_out.size() / 2, locut_cutoff_hz * 2.0 * M_PI / OUTPUT_FREQUENCY, 0.5f);
-       }
-
-       {
-               lock_guard<mutex> lock(compressor_mutex);
-
-               // Apply a level compressor to get the general level right.
-               // Basically, if it's over about -40 dBFS, we squeeze it down to that level
-               // (or more precisely, near it, since we don't use infinite ratio),
-               // then apply a makeup gain to get it to -14 dBFS. -14 dBFS is, of course,
-               // entirely arbitrary, but from practical tests with speech, it seems to
-               // put ut around -23 LUFS, so it's a reasonable starting point for later use.
                {
-                       if (level_compressor_enabled) {
+                       lock_guard<mutex> lock(compressor_mutex);
+
+                       // Apply a level compressor to get the general level right.
+                       // Basically, if it's over about -40 dBFS, we squeeze it down to that level
+                       // (or more precisely, near it, since we don't use infinite ratio),
+                       // then apply a makeup gain to get it to -14 dBFS. -14 dBFS is, of course,
+                       // entirely arbitrary, but from practical tests with speech, it seems to
+                       // put ut around -23 LUFS, so it's a reasonable starting point for later use.
+                       if (level_compressor_enabled[bus_index]) {
                                float threshold = 0.01f;   // -40 dBFS.
                                float ratio = 20.0f;
                                float attack_time = 0.5f;
                                float release_time = 20.0f;
                                float makeup_gain = from_db(ref_level_dbfs - (-40.0f));  // +26 dB.
-                               level_compressor.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
-                               gain_staging_db = to_db(level_compressor.get_attenuation() * makeup_gain);
+                               level_compressor[bus_index]->process(samples_bus.data(), samples_bus.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
+                               gain_staging_db[bus_index] = to_db(level_compressor[bus_index]->get_attenuation() * makeup_gain);
                        } else {
                                // Just apply the gain we already had.
-                               float g = from_db(gain_staging_db);
-                               for (size_t i = 0; i < samples_out.size(); ++i) {
-                                       samples_out[i] *= g;
-                               }
+                               float db = gain_staging_db[bus_index];
+                               float last_db = last_gain_staging_db[bus_index];
+                               apply_gain(db, last_db, &samples_bus);
+                       }
+                       last_gain_staging_db[bus_index] = gain_staging_db[bus_index];
+
+#if 0
+                       printf("level=%f (%+5.2f dBFS) attenuation=%f (%+5.2f dB) end_result=%+5.2f dB\n",
+                               level_compressor.get_level(), to_db(level_compressor.get_level()),
+                               level_compressor.get_attenuation(), to_db(level_compressor.get_attenuation()),
+                               to_db(level_compressor.get_level() * level_compressor.get_attenuation() * makeup_gain));
+#endif
+
+                       // The real compressor.
+                       if (compressor_enabled[bus_index]) {
+                               float threshold = from_db(compressor_threshold_dbfs[bus_index]);
+                               float ratio = 20.0f;
+                               float attack_time = 0.005f;
+                               float release_time = 0.040f;
+                               float makeup_gain = 2.0f;  // +6 dB.
+                               compressor[bus_index]->process(samples_bus.data(), samples_bus.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
+               //              compressor_att = compressor.get_attenuation();
                        }
                }
 
-       #if 0
-               printf("level=%f (%+5.2f dBFS) attenuation=%f (%+5.2f dB) end_result=%+5.2f dB\n",
-                       level_compressor.get_level(), to_db(level_compressor.get_level()),
-                       level_compressor.get_attenuation(), to_db(level_compressor.get_attenuation()),
-                       to_db(level_compressor.get_level() * level_compressor.get_attenuation() * makeup_gain));
-       #endif
-
-       //      float limiter_att, compressor_att;
-
-               // The real compressor.
-               if (compressor_enabled) {
-                       float threshold = from_db(compressor_threshold_dbfs);
-                       float ratio = 20.0f;
-                       float attack_time = 0.005f;
-                       float release_time = 0.040f;
-                       float makeup_gain = 2.0f;  // +6 dB.
-                       compressor.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
-       //              compressor_att = compressor.get_attenuation();
-               }
+               add_bus_to_master(bus_index, samples_bus, &samples_out);
+               deinterleave_samples(samples_bus, &left, &right);
+               measure_bus_levels(bus_index, left, right);
+       }
+
+       {
+               lock_guard<mutex> lock(compressor_mutex);
 
                // Finally a limiter at -4 dB (so, -10 dBFS) to take out the worst peaks only.
                // Note that since ratio is not infinite, we could go slightly higher than this.
@@ -355,7 +569,8 @@ vector<float> AudioMixer::get_output(double pts, unsigned num_samples, Resamplin
        //      printf("limiter=%+5.1f  compressor=%+5.1f\n", to_db(limiter_att), to_db(compressor_att));
        }
 
-       // At this point, we are most likely close to +0 LU, but all of our
+       // At this point, we are most likely close to +0 LU (at least if the
+       // faders sum to 0 dB and the compressors are on), but all of our
        // measurements have been on raw sample values, not R128 values.
        // So we have a final makeup gain to get us to +0 LU; the gain
        // adjustments required should be relatively small, and also, the
@@ -367,14 +582,13 @@ vector<float> AudioMixer::get_output(double pts, unsigned num_samples, Resamplin
        // Note that there's a feedback loop here, so we choose a very slow filter
        // (half-time of 30 seconds).
        double target_loudness_factor, alpha;
-       double loudness_lu = loudness_lufs - ref_level_lufs;
-       double current_makeup_lu = to_db(final_makeup_gain);
+       double loudness_lu = r128.loudness_M() - ref_level_lufs;
        target_loudness_factor = final_makeup_gain * from_db(-loudness_lu);
 
-       // If we're outside +/- 5 LU uncorrected, we don't count it as
+       // If we're outside +/- 5 LU (after correction), we don't count it as
        // a normal signal (probably silence) and don't change the
        // correction factor; just apply what we already have.
-       if (fabs(loudness_lu - current_makeup_lu) >= 5.0 || !final_makeup_gain_auto) {
+       if (fabs(loudness_lu) >= 5.0 || !final_makeup_gain_auto) {
                alpha = 0.0;
        } else {
                // Formula adapted from
@@ -395,39 +609,352 @@ vector<float> AudioMixer::get_output(double pts, unsigned num_samples, Resamplin
                final_makeup_gain = m;
        }
 
+       update_meters(samples_out);
+
        return samples_out;
 }
 
-map<DeviceSpec, DeviceInfo> AudioMixer::get_devices() const
+namespace {
+
+void apply_filter_fade(StereoFilter *filter, float *data, unsigned num_samples, float cutoff_hz, float db, float last_db)
 {
-       lock_guard<mutex> lock(audio_mutex);
+       // A granularity of 32 samples is an okay tradeoff between speed and
+       // smoothness; recalculating the filters is pretty expensive, so it's
+       // good that we don't do this all the time.
+       static constexpr unsigned filter_granularity_samples = 32;
+
+       const float cutoff_linear = cutoff_hz * 2.0 * M_PI / OUTPUT_FREQUENCY;
+       if (fabs(db - last_db) < 1e-3) {
+               // Constant over this frame.
+               if (fabs(db) > 0.01f) {
+                       filter->render(data, num_samples, cutoff_linear, 0.5f, db / 40.0f);
+               }
+       } else {
+               // We need to do a fade. (Rounding up avoids division by zero.)
+               unsigned num_blocks = (num_samples + filter_granularity_samples - 1) / filter_granularity_samples;
+               const float inc_db_norm = (db - last_db) / 40.0f / num_blocks;
+               float db_norm = db / 40.0f;
+               for (size_t i = 0; i < num_samples; i += filter_granularity_samples) {
+                       size_t samples_this_block = std::min<size_t>(num_samples - i, filter_granularity_samples);
+                       filter->render(data + i * 2, samples_this_block, cutoff_linear, 0.5f, db_norm);
+                       db_norm += inc_db_norm;
+               }
+       }
+}
+
+}  // namespace
+
+void AudioMixer::apply_eq(unsigned bus_index, vector<float> *samples_bus)
+{
+       constexpr float bass_freq_hz = 200.0f;
+       constexpr float treble_freq_hz = 4700.0f;
+
+       // Cut away everything under 120 Hz (or whatever the cutoff is);
+       // we don't need it for voice, and it will reduce headroom
+       // and confuse the compressor. (In particular, any hums at 50 or 60 Hz
+       // should be dampened.)
+       if (locut_enabled[bus_index]) {
+               locut[bus_index].render(samples_bus->data(), samples_bus->size() / 2, locut_cutoff_hz * 2.0 * M_PI / OUTPUT_FREQUENCY, 0.5f);
+       }
+
+       // Apply the rest of the EQ. Since we only have a simple three-band EQ,
+       // we can implement it with two shelf filters. We use a simple gain to
+       // set the mid-level filter, and then offset the low and high bands
+       // from that if we need to. (We could perhaps have folded the gain into
+       // the next part, but it's so cheap that the trouble isn't worth it.)
+       //
+       // If any part of the EQ has changed appreciably since last frame,
+       // we fade smoothly during the course of this frame.
+       const float bass_db = eq_level_db[bus_index][EQ_BAND_BASS];
+       const float mid_db = eq_level_db[bus_index][EQ_BAND_MID];
+       const float treble_db = eq_level_db[bus_index][EQ_BAND_TREBLE];
+
+       const float last_bass_db = last_eq_level_db[bus_index][EQ_BAND_BASS];
+       const float last_mid_db = last_eq_level_db[bus_index][EQ_BAND_MID];
+       const float last_treble_db = last_eq_level_db[bus_index][EQ_BAND_TREBLE];
+
+       assert(samples_bus->size() % 2 == 0);
+       const unsigned num_samples = samples_bus->size() / 2;
+
+       apply_gain(mid_db, last_mid_db, samples_bus);
+
+       apply_filter_fade(&eq[bus_index][EQ_BAND_BASS], samples_bus->data(), num_samples, bass_freq_hz, bass_db - mid_db, last_bass_db - last_mid_db);
+       apply_filter_fade(&eq[bus_index][EQ_BAND_TREBLE], samples_bus->data(), num_samples, treble_freq_hz, treble_db - mid_db, last_treble_db - last_mid_db);
+
+       last_eq_level_db[bus_index][EQ_BAND_BASS] = bass_db;
+       last_eq_level_db[bus_index][EQ_BAND_MID] = mid_db;
+       last_eq_level_db[bus_index][EQ_BAND_TREBLE] = treble_db;
+}
+
+void AudioMixer::add_bus_to_master(unsigned bus_index, const vector<float> &samples_bus, vector<float> *samples_out)
+{
+       assert(samples_bus.size() == samples_out->size());
+       assert(samples_bus.size() % 2 == 0);
+       unsigned num_samples = samples_bus.size() / 2;
+       const float new_volume_db = mute[bus_index] ? -90.0f : fader_volume_db[bus_index].load();
+       if (fabs(new_volume_db - last_fader_volume_db[bus_index]) > 1e-3) {
+               // The volume has changed; do a fade over the course of this frame.
+               // (We might have some numerical issues here, but it seems to sound OK.)
+               // For the purpose of fading here, the silence floor is set to -90 dB
+               // (the fader only goes to -84).
+               float old_volume = from_db(max<float>(last_fader_volume_db[bus_index], -90.0f));
+               float volume = from_db(max<float>(new_volume_db, -90.0f));
+
+               float volume_inc = pow(volume / old_volume, 1.0 / num_samples);
+               volume = old_volume;
+               if (bus_index == 0) {
+                       for (unsigned i = 0; i < num_samples; ++i) {
+                               (*samples_out)[i * 2 + 0] = samples_bus[i * 2 + 0] * volume;
+                               (*samples_out)[i * 2 + 1] = samples_bus[i * 2 + 1] * volume;
+                               volume *= volume_inc;
+                       }
+               } else {
+                       for (unsigned i = 0; i < num_samples; ++i) {
+                               (*samples_out)[i * 2 + 0] += samples_bus[i * 2 + 0] * volume;
+                               (*samples_out)[i * 2 + 1] += samples_bus[i * 2 + 1] * volume;
+                               volume *= volume_inc;
+                       }
+               }
+       } else if (new_volume_db > -90.0f) {
+               float volume = from_db(new_volume_db);
+               if (bus_index == 0) {
+                       for (unsigned i = 0; i < num_samples; ++i) {
+                               (*samples_out)[i * 2 + 0] = samples_bus[i * 2 + 0] * volume;
+                               (*samples_out)[i * 2 + 1] = samples_bus[i * 2 + 1] * volume;
+                       }
+               } else {
+                       for (unsigned i = 0; i < num_samples; ++i) {
+                               (*samples_out)[i * 2 + 0] += samples_bus[i * 2 + 0] * volume;
+                               (*samples_out)[i * 2 + 1] += samples_bus[i * 2 + 1] * volume;
+                       }
+               }
+       }
+
+       last_fader_volume_db[bus_index] = new_volume_db;
+}
+
+void AudioMixer::measure_bus_levels(unsigned bus_index, const vector<float> &left, const vector<float> &right)
+{
+       assert(left.size() == right.size());
+       const float volume = mute[bus_index] ? 0.0f : from_db(fader_volume_db[bus_index]);
+       const float peak_levels[2] = {
+               find_peak(left.data(), left.size()) * volume,
+               find_peak(right.data(), right.size()) * volume
+       };
+       for (unsigned channel = 0; channel < 2; ++channel) {
+               // Compute the current value, including hold and falloff.
+               // The constants are borrowed from zita-mu1 by Fons Adriaensen.
+               static constexpr float hold_sec = 0.5f;
+               static constexpr float falloff_db_sec = 15.0f;  // dB/sec falloff after hold.
+               float current_peak;
+               PeakHistory &history = peak_history[bus_index][channel];
+               history.historic_peak = max(history.historic_peak, peak_levels[channel]);
+               if (history.age_seconds < hold_sec) {
+                       current_peak = history.last_peak;
+               } else {
+                       current_peak = history.last_peak * from_db(-falloff_db_sec * (history.age_seconds - hold_sec));
+               }
+
+               // See if we have a new peak to replace the old (possibly falling) one.
+               if (peak_levels[channel] > current_peak) {
+                       history.last_peak = peak_levels[channel];
+                       history.age_seconds = 0.0f;  // Not 100% correct, but more than good enough given our frame sizes.
+                       current_peak = peak_levels[channel];
+               } else {
+                       history.age_seconds += float(left.size()) / OUTPUT_FREQUENCY;
+               }
+               history.current_level = peak_levels[channel];
+               history.current_peak = current_peak;
+       }
+}
+
+void AudioMixer::update_meters(const vector<float> &samples)
+{
+       // Upsample 4x to find interpolated peak.
+       peak_resampler.inp_data = const_cast<float *>(samples.data());
+       peak_resampler.inp_count = samples.size() / 2;
+
+       vector<float> interpolated_samples;
+       interpolated_samples.resize(samples.size());
+       {
+               lock_guard<mutex> lock(audio_measure_mutex);
+
+               while (peak_resampler.inp_count > 0) {  // About four iterations.
+                       peak_resampler.out_data = &interpolated_samples[0];
+                       peak_resampler.out_count = interpolated_samples.size() / 2;
+                       peak_resampler.process();
+                       size_t out_stereo_samples = interpolated_samples.size() / 2 - peak_resampler.out_count;
+                       peak = max<float>(peak, find_peak(interpolated_samples.data(), out_stereo_samples * 2));
+                       peak_resampler.out_data = nullptr;
+               }
+       }
+
+       // Find R128 levels and L/R correlation.
+       vector<float> left, right;
+       deinterleave_samples(samples, &left, &right);
+       float *ptrs[] = { left.data(), right.data() };
+       {
+               lock_guard<mutex> lock(audio_measure_mutex);
+               r128.process(left.size(), ptrs);
+               correlation.process_samples(samples);
+       }
+
+       send_audio_level_callback();
+}
+
+void AudioMixer::reset_meters()
+{
+       lock_guard<mutex> lock(audio_measure_mutex);
+       peak_resampler.reset();
+       peak = 0.0f;
+       r128.reset();
+       r128.integr_start();
+       correlation.reset();
+}
+
+void AudioMixer::send_audio_level_callback()
+{
+       if (audio_level_callback == nullptr) {
+               return;
+       }
+
+       lock_guard<mutex> lock(audio_measure_mutex);
+       double loudness_s = r128.loudness_S();
+       double loudness_i = r128.integrated();
+       double loudness_range_low = r128.range_min();
+       double loudness_range_high = r128.range_max();
+
+       vector<BusLevel> bus_levels;
+       bus_levels.resize(input_mapping.buses.size());
+       {
+               lock_guard<mutex> lock(compressor_mutex);
+               for (unsigned bus_index = 0; bus_index < bus_levels.size(); ++bus_index) {
+                       bus_levels[bus_index].current_level_dbfs[0] = to_db(peak_history[bus_index][0].current_level);
+                       bus_levels[bus_index].current_level_dbfs[1] = to_db(peak_history[bus_index][1].current_level);
+                       bus_levels[bus_index].peak_level_dbfs[0] = to_db(peak_history[bus_index][0].current_peak);
+                       bus_levels[bus_index].peak_level_dbfs[1] = to_db(peak_history[bus_index][1].current_peak);
+                       bus_levels[bus_index].historic_peak_dbfs = to_db(
+                               max(peak_history[bus_index][0].historic_peak,
+                                   peak_history[bus_index][1].historic_peak));
+                       bus_levels[bus_index].gain_staging_db = gain_staging_db[bus_index];
+                       if (compressor_enabled[bus_index]) {
+                               bus_levels[bus_index].compressor_attenuation_db = -to_db(compressor[bus_index]->get_attenuation());
+                       } else {
+                               bus_levels[bus_index].compressor_attenuation_db = 0.0;
+                       }
+               }
+       }
+
+       audio_level_callback(loudness_s, to_db(peak), bus_levels,
+               loudness_i, loudness_range_low, loudness_range_high,
+               to_db(final_makeup_gain),
+               correlation.get_correlation());
+}
+
+map<DeviceSpec, DeviceInfo> AudioMixer::get_devices()
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+
        map<DeviceSpec, DeviceInfo> devices;
        for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                const DeviceSpec spec{ InputSourceType::CAPTURE_CARD, card_index };
                const AudioDevice *device = &video_cards[card_index];
                DeviceInfo info;
-               info.name = device->name;
-               info.num_channels = 8;  // FIXME: This is wrong for fake cards.
+               info.display_name = device->display_name;
+               info.num_channels = 8;
+               devices.insert(make_pair(spec, info));
+       }
+       vector<ALSAPool::Device> available_alsa_devices = alsa_pool.get_devices();
+       for (unsigned card_index = 0; card_index < available_alsa_devices.size(); ++card_index) {
+               const DeviceSpec spec{ InputSourceType::ALSA_INPUT, card_index };
+               const ALSAPool::Device &device = available_alsa_devices[card_index];
+               DeviceInfo info;
+               info.display_name = device.display_name();
+               info.num_channels = device.num_channels;
+               info.alsa_name = device.name;
+               info.alsa_info = device.info;
+               info.alsa_address = device.address;
                devices.insert(make_pair(spec, info));
        }
        return devices;
 }
 
-void AudioMixer::set_name(DeviceSpec device_spec, const string &name)
+void AudioMixer::set_display_name(DeviceSpec device_spec, const string &name)
 {
        AudioDevice *device = find_audio_device(device_spec);
 
-       lock_guard<mutex> lock(audio_mutex);
-       device->name = name;
+       lock_guard<timed_mutex> lock(audio_mutex);
+       device->display_name = name;
+}
+
+void AudioMixer::serialize_device(DeviceSpec device_spec, DeviceSpecProto *device_spec_proto)
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       switch (device_spec.type) {
+               case InputSourceType::SILENCE:
+                       device_spec_proto->set_type(DeviceSpecProto::SILENCE);
+                       break;
+               case InputSourceType::CAPTURE_CARD:
+                       device_spec_proto->set_type(DeviceSpecProto::CAPTURE_CARD);
+                       device_spec_proto->set_index(device_spec.index);
+                       device_spec_proto->set_display_name(video_cards[device_spec.index].display_name);
+                       break;
+               case InputSourceType::ALSA_INPUT:
+                       alsa_pool.serialize_device(device_spec.index, device_spec_proto);
+                       break;
+       }
+}
+
+void AudioMixer::set_simple_input(unsigned card_index)
+{
+       InputMapping new_input_mapping;
+       InputMapping::Bus input;
+       input.name = "Main";
+       input.device.type = InputSourceType::CAPTURE_CARD;
+       input.device.index = card_index;
+       input.source_channel[0] = 0;
+       input.source_channel[1] = 1;
+
+       new_input_mapping.buses.push_back(input);
+
+       lock_guard<timed_mutex> lock(audio_mutex);
+       current_mapping_mode = MappingMode::SIMPLE;
+       set_input_mapping_lock_held(new_input_mapping);
+       fader_volume_db[0] = 0.0f;
+}
+
+unsigned AudioMixer::get_simple_input() const
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       if (input_mapping.buses.size() == 1 &&
+           input_mapping.buses[0].device.type == InputSourceType::CAPTURE_CARD &&
+           input_mapping.buses[0].source_channel[0] == 0 &&
+           input_mapping.buses[0].source_channel[1] == 1) {
+               return input_mapping.buses[0].device.index;
+       } else {
+               return numeric_limits<unsigned>::max();
+       }
 }
 
 void AudioMixer::set_input_mapping(const InputMapping &new_input_mapping)
 {
-       lock_guard<mutex> lock(audio_mutex);
+       lock_guard<timed_mutex> lock(audio_mutex);
+       set_input_mapping_lock_held(new_input_mapping);
+       current_mapping_mode = MappingMode::MULTICHANNEL;
+}
 
+AudioMixer::MappingMode AudioMixer::get_mapping_mode() const
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       return current_mapping_mode;
+}
+
+void AudioMixer::set_input_mapping_lock_held(const InputMapping &new_input_mapping)
+{
        map<DeviceSpec, set<unsigned>> interesting_channels;
        for (const InputMapping::Bus &bus : new_input_mapping.buses) {
-               if (bus.device.type == InputSourceType::CAPTURE_CARD) {
+               if (bus.device.type == InputSourceType::CAPTURE_CARD ||
+                   bus.device.type == InputSourceType::ALSA_INPUT) {
                        for (unsigned channel = 0; channel < 2; ++channel) {
                                if (bus.source_channel[channel] != -1) {
                                        interesting_channels[bus.device].insert(bus.source_channel[channel]);
@@ -437,12 +964,26 @@ void AudioMixer::set_input_mapping(const InputMapping &new_input_mapping)
        }
 
        // Reset resamplers for all cards that don't have the exact same state as before.
-       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
-               DeviceSpec device_spec{InputSourceType::CAPTURE_CARD, card_index};
-               AudioDevice *device = &video_cards[card_index];
+       for (unsigned card_index = 0; card_index < MAX_VIDEO_CARDS; ++card_index) {
+               const DeviceSpec device_spec{InputSourceType::CAPTURE_CARD, card_index};
+               AudioDevice *device = find_audio_device(device_spec);
                if (device->interesting_channels != interesting_channels[device_spec]) {
                        device->interesting_channels = interesting_channels[device_spec];
-                       reset_device_mutex_held(DeviceSpec{InputSourceType::CAPTURE_CARD, card_index});
+                       reset_resampler_mutex_held(device_spec);
+               }
+       }
+       for (unsigned card_index = 0; card_index < MAX_ALSA_CARDS; ++card_index) {
+               const DeviceSpec device_spec{InputSourceType::ALSA_INPUT, card_index};
+               AudioDevice *device = find_audio_device(device_spec);
+               if (interesting_channels[device_spec].empty()) {
+                       alsa_pool.release_device(card_index);
+               } else {
+                       alsa_pool.hold_device(card_index);
+               }
+               if (device->interesting_channels != interesting_channels[device_spec]) {
+                       device->interesting_channels = interesting_channels[device_spec];
+                       alsa_pool.reset_device(device_spec.index);
+                       reset_resampler_mutex_held(device_spec);
                }
        }
 
@@ -451,6 +992,27 @@ void AudioMixer::set_input_mapping(const InputMapping &new_input_mapping)
 
 InputMapping AudioMixer::get_input_mapping() const
 {
-       lock_guard<mutex> lock(audio_mutex);
+       lock_guard<timed_mutex> lock(audio_mutex);
        return input_mapping;
 }
+
+unsigned AudioMixer::num_buses() const
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       return input_mapping.buses.size();
+}
+
+void AudioMixer::reset_peak(unsigned bus_index)
+{
+       lock_guard<timed_mutex> lock(audio_mutex);
+       for (unsigned channel = 0; channel < 2; ++channel) {
+               PeakHistory &history = peak_history[bus_index][channel];
+               history.current_level = 0.0f;
+               history.historic_peak = 0.0f;
+               history.current_peak = 0.0f;
+               history.last_peak = 0.0f;
+               history.age_seconds = 0.0f;
+       }
+}
+
+AudioMixer *global_audio_mixer = nullptr;