]> git.sesse.net Git - nageru/blobdiff - mixer.cpp
Support true variable input frame rate instead of hard-coding to 60.
[nageru] / mixer.cpp
index e85710c25c519bfbd261c6ab6cf81cb2014f4796..936a070129352c4b10a80747e740be1e1ebb2dd0 100644 (file)
--- a/mixer.cpp
+++ b/mixer.cpp
@@ -1,5 +1,3 @@
-#define WIDTH 1280
-#define HEIGHT 720
 #define EXTRAHEIGHT 30
 
 #undef Success
@@ -7,27 +5,20 @@
 #include "mixer.h"
 
 #include <assert.h>
-#include <effect.h>
-#include <effect_chain.h>
-#include <effect_util.h>
 #include <epoxy/egl.h>
-#include <features.h>
-#include <image_format.h>
 #include <init.h>
-#include <overlay_effect.h>
-#include <padding_effect.h>
-#include <resample_effect.h>
-#include <resource_pool.h>
-#include <saturation_effect.h>
+#include <movit/effect_chain.h>
+#include <movit/effect_util.h>
+#include <movit/flat_input.h>
+#include <movit/image_format.h>
+#include <movit/resource_pool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/time.h>
 #include <time.h>
 #include <util.h>
-#include <white_balance_effect.h>
-#include <ycbcr.h>
-#include <ycbcr_input.h>
+#include <algorithm>
 #include <cmath>
 #include <condition_variable>
 #include <cstddef>
 #include <mutex>
 #include <string>
 #include <thread>
+#include <utility>
 #include <vector>
 
 #include "bmusb/bmusb.h"
 #include "context.h"
+#include "defs.h"
 #include "h264encode.h"
 #include "pbo_frame_allocator.h"
 #include "ref_counted_gl_sync.h"
@@ -70,22 +63,29 @@ void convert_fixed24_to_fp32(float *dst, size_t out_channels, const uint8_t *src
 
 }  // namespace
 
-Mixer::Mixer(const QSurfaceFormat &format)
-       : httpd("test.ts", WIDTH, HEIGHT),
+Mixer::Mixer(const QSurfaceFormat &format, unsigned num_cards)
+       : httpd(LOCAL_DUMP_FILE_NAME, WIDTH, HEIGHT),
+         num_cards(num_cards),
          mixer_surface(create_surface(format)),
-         h264_encoder_surface(create_surface(format))
+         h264_encoder_surface(create_surface(format)),
+         level_compressor(OUTPUT_FREQUENCY),
+         limiter(OUTPUT_FREQUENCY),
+         compressor(OUTPUT_FREQUENCY)
 {
        httpd.start(9095);
 
        CHECK(init_movit(MOVIT_SHADER_DIR, MOVIT_DEBUG_OFF));
        check_error();
 
+       // Since we allow non-bouncing 4:2:2 YCbCrInputs, effective subpixel precision
+       // will be halved when sampling them, and we need to compensate here.
+       movit_texel_subpixel_precision /= 2.0;
+
        resource_pool.reset(new ResourcePool);
-       theme.reset(new Theme("theme.lua", resource_pool.get()));
-       output_channel[OUTPUT_LIVE].parent = this;
-       output_channel[OUTPUT_PREVIEW].parent = this;
-       output_channel[OUTPUT_INPUT0].parent = this;
-       output_channel[OUTPUT_INPUT1].parent = this;
+       theme.reset(new Theme("theme.lua", resource_pool.get(), num_cards));
+       for (unsigned i = 0; i < NUM_OUTPUTS; ++i) {
+               output_channel[i].parent = this;
+       }
 
        ImageFormat inout_format;
        inout_format.color_space = COLORSPACE_sRGB;
@@ -102,7 +102,7 @@ Mixer::Mixer(const QSurfaceFormat &format)
 
        h264_encoder.reset(new H264Encoder(h264_encoder_surface, WIDTH, HEIGHT, &httpd));
 
-       for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                printf("Configuring card %d...\n", card_index);
                CaptureCard *card = &cards[card_index];
                card->usb = new BMUSBCapture(card_index);
@@ -113,7 +113,7 @@ Mixer::Mixer(const QSurfaceFormat &format)
                card->usb->set_dequeue_thread_callbacks(
                        [card]{
                                eglBindAPI(EGL_OPENGL_API);
-                               card->context = create_context();
+                               card->context = create_context(card->surface);
                                if (!make_current(card->context, card->surface)) {
                                        printf("failed to create bmusb context\n");
                                        exit(1);
@@ -122,13 +122,13 @@ Mixer::Mixer(const QSurfaceFormat &format)
                        [this]{
                                resource_pool->clean_context();
                        });
-               card->resampler.reset(new Resampler(48000.0, 48000.0, 2));
+               card->resampling_queue.reset(new ResamplingQueue(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY, 2));
                card->usb->configure_card();
        }
 
        BMUSBCapture::start_bm_thread();
 
-       for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                cards[card_index].usb->start_bm_capture();
        }
 
@@ -147,8 +147,16 @@ Mixer::Mixer(const QSurfaceFormat &format)
                "} \n";
        cbcr_program_num = resource_pool->compile_glsl_program(cbcr_vert_shader, cbcr_frag_shader);
 
-       r128.init(2, 48000);
+       r128.init(2, OUTPUT_FREQUENCY);
        r128.integr_start();
+
+       locut.init(FILTER_HPF, 2);
+
+       // 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);
+
+       alsa.reset(new ALSAOutput(OUTPUT_FREQUENCY, /*num_channels=*/2));
 }
 
 Mixer::~Mixer()
@@ -156,7 +164,7 @@ Mixer::~Mixer()
        resource_pool->release_glsl_program(cbcr_program_num);
        BMUSBCapture::stop_bm_thread();
 
-       for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                {
                        unique_lock<mutex> lock(bmusb_mutex);
                        cards[card_index].should_quit = true;  // Unblock thread.
@@ -164,6 +172,8 @@ Mixer::~Mixer()
                }
                cards[card_index].usb->stop_dequeue_thread();
        }
+
+       h264_encoder.reset(nullptr);
 }
 
 namespace {
@@ -178,10 +188,10 @@ int unwrap_timecode(uint16_t current_wrapped, int last)
        }
 }
 
-float find_peak(const vector<float> &samples)
+float find_peak(const float *samples, size_t num_samples)
 {
        float m = fabs(samples[0]);
-       for (size_t i = 1; i < samples.size(); ++i) {
+       for (size_t i = 1; i < num_samples; ++i) {
                m = std::max(m, fabs(samples[i]));
        }
        return m;
@@ -202,14 +212,67 @@ void deinterleave_samples(const vector<float> &in, vector<float> *out_l, vector<
        }
 }
 
+// Returns length of a frame with the given format, in TIMEBASE units.
+int64_t find_frame_length(uint16_t video_format)
+{
+       if (video_format == 0x0800) {
+               // No video signal. These green pseudo-frames seem to come at about 30.13 Hz.
+               // It's a strange thing, but what can you do.
+               return TIMEBASE * 100 / 3013;
+       }
+       if ((video_format & 0xe800) != 0xe800) {
+               printf("Video format 0x%04x does not appear to be a video format. Assuming 60 Hz.\n",
+                       video_format);
+               return TIMEBASE / 60;
+       }
+
+       // 0x8 seems to be a flag about availability of deep color on the input,
+       // except when it's not (e.g. it's the only difference between NTSC 23.98
+       // and PAL). Rather confusing. But we clear it here nevertheless, because
+       // usually it doesn't mean anything.
+       //
+       // We don't really handle interlaced formats at all yet.
+       uint16_t normalized_video_format = video_format & ~0xe808;
+       if (normalized_video_format == 0x0143) {         // 720p50.
+               return TIMEBASE / 50;
+       } else if (normalized_video_format == 0x0103) {  // 720p60.
+               return TIMEBASE / 60;
+       } else if (normalized_video_format == 0x0121) {  // 720p59.94.
+               return TIMEBASE * 1001 / 60000;
+       } else if (normalized_video_format == 0x01c3 ||  // 1080p30.
+                  normalized_video_format == 0x0003) {  // 1080i60.
+               return TIMEBASE / 30;
+       } else if (normalized_video_format == 0x01e1 ||  // 1080p29.97.
+                  normalized_video_format == 0x0021 ||  // 1080i59.94.
+                  video_format == 0xe901 ||             // NTSC (480i59.94, I suppose).
+                  video_format == 0xe9c1 ||             // Ditto.
+                  video_format == 0xe801) {             // Ditto.
+               return TIMEBASE * 1001 / 30000;
+       } else if (normalized_video_format == 0x0063 ||  // 1080p25.
+                  normalized_video_format == 0x0043 ||  // 1080i50.
+                  video_format == 0xe909) {             // PAL (576i50, I suppose).
+               return TIMEBASE / 25;
+       } else if (normalized_video_format == 0x008e) {  // 1080p24.
+               return TIMEBASE / 24;
+       } else if (normalized_video_format == 0x00a1) {  // 1080p23.98.
+               return TIMEBASE * 1001 / 24000;
+               return TIMEBASE / 25;
+       } else {
+               printf("Unknown video format 0x%04x. Assuming 60 Hz.\n", video_format);
+               return TIMEBASE / 60;
+       }
+}
+
 }  // namespace
 
-void Mixer::bm_frame(int card_index, uint16_t timecode,
+void Mixer::bm_frame(unsigned card_index, uint16_t timecode,
                      FrameAllocator::Frame video_frame, size_t video_offset, uint16_t video_format,
                     FrameAllocator::Frame audio_frame, size_t audio_offset, uint16_t audio_format)
 {
        CaptureCard *card = &cards[card_index];
 
+       int64_t frame_length = find_frame_length(video_format);
+
        if (audio_frame.len - audio_offset > 30000) {
                printf("Card %d: Dropping frame with implausible audio length (len=%d, offset=%d) [timecode=0x%04x video_len=%d video_offset=%d video_format=%x)\n",
                        card_index, int(audio_frame.len), int(audio_offset),
@@ -223,40 +286,44 @@ void Mixer::bm_frame(int card_index, uint16_t timecode,
                return;
        }
 
+       int64_t local_pts = card->next_local_pts;
+       int dropped_frames = 0;
+       if (card->last_timecode != -1) {
+               dropped_frames = unwrap_timecode(timecode, card->last_timecode) - card->last_timecode - 1;
+       }
+       card->last_timecode = timecode;
+
        // Convert the audio to stereo fp32 and add it.
-       size_t num_samples = (audio_frame.len - audio_offset) / 8 / 3;
+       size_t num_samples = (audio_frame.len >= audio_offset) ? (audio_frame.len - audio_offset) / 8 / 3 : 0;
        vector<float> audio;
        audio.resize(num_samples * 2);
        convert_fixed24_to_fp32(&audio[0], 2, audio_frame.data + audio_offset, 8, num_samples);
 
-       int unwrapped_timecode = timecode;
-       int dropped_frames = 0;
-       if (card->last_timecode != -1) {
-               unwrapped_timecode = unwrap_timecode(unwrapped_timecode, card->last_timecode);
-               dropped_frames = unwrapped_timecode - card->last_timecode - 1;
-       }
-       card->last_timecode = unwrapped_timecode;
-
        // Add the audio.
        {
                unique_lock<mutex> lock(card->audio_mutex);
 
-               int unwrapped_timecode = timecode;
-               if (dropped_frames > 60 * 2) {
+               if (dropped_frames > MAX_FPS * 2) {
                        fprintf(stderr, "Card %d lost more than two seconds (or time code jumping around), resetting resampler\n",
                                card_index);
-                       card->resampler.reset(new Resampler(48000.0, 48000.0, 2));
+                       card->resampling_queue.reset(new ResamplingQueue(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY, 2));
                } else if (dropped_frames > 0) {
-                       // Insert silence as needed.
+                       // Insert silence as needed. (The number of samples could be nonintegral,
+                       // but resampling will save us then.)
                        fprintf(stderr, "Card %d dropped %d frame(s) (before timecode 0x%04x), inserting silence.\n",
                                card_index, dropped_frames, timecode);
                        vector<float> silence;
-                       silence.resize((48000 / 60) * 2);
+                       silence.resize((OUTPUT_FREQUENCY * frame_length / TIMEBASE) * 2);
                        for (int i = 0; i < dropped_frames; ++i) {
-                               card->resampler->add_input_samples((unwrapped_timecode - dropped_frames + i) / 60.0, silence.data(), (48000 / 60));
+                               card->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), silence.data(), silence.size() / 2);
+                               // Note that if the format changed in the meantime, we have
+                               // no way of detecting that; we just have to assume the frame length
+                               // is always the same.
+                               local_pts += frame_length;
                        }
                }
-               card->resampler->add_input_samples(unwrapped_timecode / 60.0, audio.data(), num_samples);
+               card->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), audio.data(), num_samples);
+               card->next_local_pts = local_pts + frame_length;
        }
 
        // Done with the audio, so release it.
@@ -286,6 +353,7 @@ void Mixer::bm_frame(int card_index, uint16_t timecode,
                        unique_lock<mutex> lock(bmusb_mutex);
                        card->new_data_ready = true;
                        card->new_frame = RefCountedFrame(FrameAllocator::Frame());
+                       card->new_frame_length = frame_length;
                        card->new_data_ready_fence = nullptr;
                        card->dropped_frames = dropped_frames;
                        card->new_data_ready_changed.notify_all();
@@ -322,6 +390,7 @@ void Mixer::bm_frame(int card_index, uint16_t timecode,
                unique_lock<mutex> lock(bmusb_mutex);
                card->new_data_ready = true;
                card->new_frame = RefCountedFrame(video_frame);
+               card->new_frame_length = frame_length;
                card->new_data_ready_fence = fence;
                card->dropped_frames = dropped_frames;
                card->new_data_ready_changed.notify_all();
@@ -331,7 +400,7 @@ void Mixer::bm_frame(int card_index, uint16_t timecode,
 void Mixer::thread_func()
 {
        eglBindAPI(EGL_OPENGL_API);
-       QOpenGLContext *context = create_context();
+       QOpenGLContext *context = create_context(mixer_surface);
        if (!make_current(context, mixer_surface)) {
                printf("oops\n");
                exit(1);
@@ -344,7 +413,8 @@ void Mixer::thread_func()
        int dropped_frames = 0;
 
        while (!should_quit) {
-               CaptureCard card_copy[NUM_CARDS];
+               CaptureCard card_copy[MAX_CARDS];
+               int num_samples[MAX_CARDS];
 
                {
                        unique_lock<mutex> lock(bmusb_mutex);
@@ -353,44 +423,37 @@ void Mixer::thread_func()
                        // TODO: Make configurable, and with a timeout.
                        cards[0].new_data_ready_changed.wait(lock, [this]{ return cards[0].new_data_ready; });
 
-                       for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+                       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                                CaptureCard *card = &cards[card_index];
                                card_copy[card_index].usb = card->usb;
                                card_copy[card_index].new_data_ready = card->new_data_ready;
                                card_copy[card_index].new_frame = card->new_frame;
+                               card_copy[card_index].new_frame_length = card->new_frame_length;
                                card_copy[card_index].new_data_ready_fence = card->new_data_ready_fence;
-                               card_copy[card_index].new_frame_audio = move(card->new_frame_audio);
                                card_copy[card_index].dropped_frames = card->dropped_frames;
                                card->new_data_ready = false;
                                card->new_data_ready_changed.notify_all();
+
+                               int num_samples_times_timebase = OUTPUT_FREQUENCY * card->new_frame_length + card->fractional_samples;
+                               num_samples[card_index] = num_samples_times_timebase / TIMEBASE;
+                               card->fractional_samples = num_samples_times_timebase % TIMEBASE;
                        }
                }
 
                // Resample the audio as needed, including from previously dropped frames.
-               vector<float> samples_out;
-               // TODO: Allow using audio from the other card(s) as well.
                for (unsigned frame_num = 0; frame_num < card_copy[0].dropped_frames + 1; ++frame_num) {
-                       for (unsigned card_index = 0; card_index < NUM_CARDS; ++card_index) {
-                               samples_out.resize((48000 / 60) * 2);
-                               {
-                                       unique_lock<mutex> lock(cards[card_index].audio_mutex);
-                                       if (!cards[card_index].resampler->get_output_samples(pts(), &samples_out[0], 48000 / 60)) {
-                                               printf("Card %d reported previous underrun.\n", card_index);
-                                       }
-                               }
-                               if (card_index == 0) {
-                                       vector<float> left, right;
-                                       peak = std::max(peak, find_peak(samples_out));
-                                       deinterleave_samples(samples_out, &left, &right);
-                                       float *ptrs[] = { left.data(), right.data() };
-                                       r128.process(left.size(), ptrs);
-                                       h264_encoder->add_audio(pts_int, move(samples_out));
-                               }
+                       {
+                               // Signal to the audio thread to process this frame.
+                               unique_lock<mutex> lock(audio_mutex);
+                               audio_task_queue.push(AudioTask{pts_int, num_samples[0]});
+                               audio_task_queue_changed.notify_one();
                        }
                        if (frame_num != card_copy[0].dropped_frames) {
-                               // For dropped frames, increase the pts.
+                               // For dropped frames, increase the pts. Note that if the format changed
+                               // in the meantime, we have no way of detecting that; we just have to
+                               // assume the frame length is always the same.
                                ++dropped_frames;
-                               pts_int += TIMEBASE / 60;
+                               pts_int += card_copy[0].new_frame_length;
                        }
                }
 
@@ -401,18 +464,29 @@ void Mixer::thread_func()
                        double loudness_range_high = r128.range_max();
 
                        audio_level_callback(loudness_s, 20.0 * log10(peak),
-                                            loudness_i, loudness_range_low, loudness_range_high);
+                                            loudness_i, loudness_range_low, loudness_range_high,
+                                            last_gain_staging_db);
+               }
+
+               for (unsigned card_index = 1; card_index < num_cards; ++card_index) {
+                       if (card_copy[card_index].new_data_ready && card_copy[card_index].new_frame->len == 0) {
+                               ++card_copy[card_index].dropped_frames;
+                       }
+                       if (card_copy[card_index].dropped_frames > 0) {
+                               printf("Card %u dropped %d frames before this\n",
+                                       card_index, int(card_copy[card_index].dropped_frames));
+                       }
                }
 
                // If the first card is reporting a corrupted or otherwise dropped frame,
                // just increase the pts (skipping over this frame) and don't try to compute anything new.
                if (card_copy[0].new_frame->len == 0) {
                        ++dropped_frames;
-                       pts_int += TIMEBASE / 60;
+                       pts_int += card_copy[0].new_frame_length;
                        continue;
                }
 
-               for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+               for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                        CaptureCard *card = &card_copy[card_index];
                        if (!card->new_data_ready || card->new_frame->len == 0)
                                continue;
@@ -467,13 +541,13 @@ void Mixer::thread_func()
                // input frames needed, so that they are not released back
                // until the rendering is done.
                vector<RefCountedFrame> input_frames;
-               for (int card_index = 0; card_index < NUM_CARDS; ++card_index) {
+               for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
                        input_frames.push_back(bmusb_current_rendering_frame[card_index]);
                }
-               const int64_t av_delay = TIMEBASE / 10;  // Corresponds to the fixed delay in resampler.h. TODO: Make less hard-coded.
+               const int64_t av_delay = TIMEBASE / 10;  // Corresponds to the fixed delay in resampling_queue.h. TODO: Make less hard-coded.
                h264_encoder->end_frame(fence, pts_int + av_delay, input_frames);
                ++frame;
-               pts_int += TIMEBASE / 60;
+               pts_int += card_copy[0].new_frame_length;
 
                // The live frame just shows the RGBA texture we just rendered.
                // It owns rgba_tex now.
@@ -494,7 +568,11 @@ void Mixer::thread_func()
                        display_frame.chain = chain.first;
                        display_frame.setup_chain = chain.second;
                        display_frame.ready_fence = fence;
-                       display_frame.input_frames = { bmusb_current_rendering_frame[0], bmusb_current_rendering_frame[1] };  // FIXME: possible to do better?
+
+                       // FIXME: possible to do better?
+                       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
+                               display_frame.input_frames.push_back(bmusb_current_rendering_frame[card_index]);
+                       }
                        display_frame.temp_textures = {};
                        output_channel[i].output_frame(display_frame);
                }
@@ -525,6 +603,126 @@ void Mixer::thread_func()
        resource_pool->clean_context();
 }
 
+void Mixer::audio_thread_func()
+{
+       while (!should_quit) {
+               AudioTask task;
+
+               {
+                       unique_lock<mutex> lock(audio_mutex);
+                       audio_task_queue_changed.wait(lock, [this]{ return !audio_task_queue.empty(); });
+                       task = audio_task_queue.front();
+                       audio_task_queue.pop();
+               }
+
+               process_audio_one_frame(task.pts_int, task.num_samples);
+       }
+}
+
+void Mixer::process_audio_one_frame(int64_t frame_pts_int, int num_samples)
+{
+       vector<float> samples_card;
+       vector<float> samples_out;
+       for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
+               samples_card.resize(num_samples * 2);
+               {
+                       unique_lock<mutex> lock(cards[card_index].audio_mutex);
+                       if (!cards[card_index].resampling_queue->get_output_samples(double(frame_pts_int) / TIMEBASE, &samples_card[0], num_samples)) {
+                               printf("Card %d reported previous underrun.\n", card_index);
+                       }
+               }
+               // TODO: Allow using audio from the other card(s) as well.
+               if (card_index == 0) {
+                       samples_out = move(samples_card);
+               }
+       }
+
+       // 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.)
+       locut.render(samples_out.data(), samples_out.size() / 2, locut_cutoff_hz * 2.0 * M_PI / OUTPUT_FREQUENCY, 0.5f);
+
+       // 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.
+       float ref_level_dbfs = -14.0f;
+       {
+               float threshold = 0.01f;   // -40 dBFS.
+               float ratio = 20.0f;
+               float attack_time = 0.5f;
+               float release_time = 20.0f;
+               float makeup_gain = pow(10.0f, (ref_level_dbfs - (-40.0f)) / 20.0f);  // +26 dB.
+               level_compressor.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
+               last_gain_staging_db = 20.0 * log10(level_compressor.get_attenuation() * makeup_gain);
+       }
+
+#if 0
+       printf("level=%f (%+5.2f dBFS) attenuation=%f (%+5.2f dB) end_result=%+5.2f dB\n",
+               level_compressor.get_level(), 20.0 * log10(level_compressor.get_level()),
+               level_compressor.get_attenuation(), 20.0 * log10(level_compressor.get_attenuation()),
+               20.0 * log10(level_compressor.get_level() * level_compressor.get_attenuation() * makeup_gain));
+#endif
+
+//     float limiter_att, compressor_att;
+
+       // The real compressor.
+       if (compressor_enabled) {
+               float threshold = pow(10.0f, compressor_threshold_dbfs / 20.0f);
+               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();
+       }
+
+       // 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.
+       if (limiter_enabled) {
+               float threshold = pow(10.0f, limiter_threshold_dbfs / 20.0f);
+               float ratio = 30.0f;
+               float attack_time = 0.0f;  // Instant.
+               float release_time = 0.020f;
+               float makeup_gain = 1.0f;  // 0 dB.
+               limiter.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
+//             limiter_att = limiter.get_attenuation();
+       }
+
+//     printf("limiter=%+5.1f  compressor=%+5.1f\n", 20.0*log10(limiter_att), 20.0*log10(compressor_att));
+
+       // Upsample 4x to find interpolated peak.
+       peak_resampler.inp_data = samples_out.data();
+       peak_resampler.inp_count = samples_out.size() / 2;
+
+       vector<float> interpolated_samples_out;
+       interpolated_samples_out.resize(samples_out.size());
+       while (peak_resampler.inp_count > 0) {  // About four iterations.
+               peak_resampler.out_data = &interpolated_samples_out[0];
+               peak_resampler.out_count = interpolated_samples_out.size() / 2;
+               peak_resampler.process();
+               size_t out_stereo_samples = interpolated_samples_out.size() / 2 - peak_resampler.out_count;
+               peak = max<float>(peak, find_peak(interpolated_samples_out.data(), out_stereo_samples * 2));
+       }
+
+       // Find R128 levels.
+       vector<float> left, right;
+       deinterleave_samples(samples_out, &left, &right);
+       float *ptrs[] = { left.data(), right.data() };
+       r128.process(left.size(), ptrs);
+
+       // Send the samples to the sound card.
+       if (alsa) {
+               alsa->write(samples_out);
+       }
+
+       // And finally add them to the output.
+       h264_encoder->add_audio(frame_pts_int, move(samples_out));
+}
+
 void Mixer::subsample_chroma(GLuint src_tex, GLuint dst_tex)
 {
        GLuint vao;
@@ -592,12 +790,14 @@ void Mixer::release_display_frame(DisplayFrame *frame)
 void Mixer::start()
 {
        mixer_thread = thread(&Mixer::thread_func, this);
+       audio_thread = thread(&Mixer::audio_thread_func, this);
 }
 
 void Mixer::quit()
 {
        should_quit = true;
        mixer_thread.join();
+       audio_thread.join();
 }
 
 void Mixer::transition_clicked(int transition_num)
@@ -610,6 +810,14 @@ void Mixer::channel_clicked(int preview_num)
        theme->channel_clicked(preview_num);
 }
 
+void Mixer::reset_meters()
+{
+       peak_resampler.reset();
+       peak = 0.0f;
+       r128.reset();
+       r128.integr_start();
+}
+
 Mixer::OutputChannel::~OutputChannel()
 {
        if (has_current_frame) {