]> git.sesse.net Git - nageru/blob - mixer.cpp
Fix crashes when cards deliver empty audio frames (especially 0-channel).
[nageru] / mixer.cpp
1 #undef Success
2
3 #include "mixer.h"
4
5 #include <assert.h>
6 #include <epoxy/egl.h>
7 #include <movit/effect_chain.h>
8 #include <movit/effect_util.h>
9 #include <movit/flat_input.h>
10 #include <movit/image_format.h>
11 #include <movit/init.h>
12 #include <movit/resource_pool.h>
13 #include <movit/util.h>
14 #include <stdint.h>
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <sys/time.h>
18 #include <time.h>
19 #include <algorithm>
20 #include <cmath>
21 #include <condition_variable>
22 #include <cstddef>
23 #include <memory>
24 #include <mutex>
25 #include <string>
26 #include <thread>
27 #include <utility>
28 #include <vector>
29 #include <arpa/inet.h>
30
31 #include "bmusb/bmusb.h"
32 #include "context.h"
33 #include "decklink_capture.h"
34 #include "defs.h"
35 #include "flags.h"
36 #include "h264encode.h"
37 #include "pbo_frame_allocator.h"
38 #include "ref_counted_gl_sync.h"
39 #include "timebase.h"
40
41 class QOpenGLContext;
42
43 using namespace movit;
44 using namespace std;
45 using namespace std::placeholders;
46
47 Mixer *global_mixer = nullptr;
48
49 namespace {
50
51 void convert_fixed24_to_fp32(float *dst, size_t out_channels, const uint8_t *src, size_t in_channels, size_t num_samples)
52 {
53         assert(in_channels >= out_channels);
54         for (size_t i = 0; i < num_samples; ++i) {
55                 for (size_t j = 0; j < out_channels; ++j) {
56                         uint32_t s1 = *src++;
57                         uint32_t s2 = *src++;
58                         uint32_t s3 = *src++;
59                         uint32_t s = s1 | (s1 << 8) | (s2 << 16) | (s3 << 24);
60                         dst[i * out_channels + j] = int(s) * (1.0f / 4294967296.0f);
61                 }
62                 src += 3 * (in_channels - out_channels);
63         }
64 }
65
66 void convert_fixed32_to_fp32(float *dst, size_t out_channels, const uint8_t *src, size_t in_channels, size_t num_samples)
67 {
68         assert(in_channels >= out_channels);
69         for (size_t i = 0; i < num_samples; ++i) {
70                 for (size_t j = 0; j < out_channels; ++j) {
71                         // Note: Assumes little-endian.
72                         int32_t s = *(int32_t *)src;
73                         dst[i * out_channels + j] = s * (1.0f / 4294967296.0f);
74                         src += 4;
75                 }
76                 src += 4 * (in_channels - out_channels);
77         }
78 }
79
80 void insert_new_frame(RefCountedFrame frame, unsigned field_num, bool interlaced, unsigned card_index, InputState *input_state)
81 {
82         if (interlaced) {
83                 for (unsigned frame_num = FRAME_HISTORY_LENGTH; frame_num --> 1; ) {  // :-)
84                         input_state->buffered_frames[card_index][frame_num] =
85                                 input_state->buffered_frames[card_index][frame_num - 1];
86                 }
87                 input_state->buffered_frames[card_index][0] = { frame, field_num };
88         } else {
89                 for (unsigned frame_num = 0; frame_num < FRAME_HISTORY_LENGTH; ++frame_num) {
90                         input_state->buffered_frames[card_index][frame_num] = { frame, field_num };
91                 }
92         }
93 }
94
95 string generate_local_dump_filename(int frame)
96 {
97         time_t now = time(NULL);
98         tm now_tm;
99         localtime_r(&now, &now_tm);
100
101         char timestamp[256];
102         strftime(timestamp, sizeof(timestamp), "%F-%T%z", &now_tm);
103
104         // Use the frame number to disambiguate between two cuts starting
105         // on the same second.
106         char filename[256];
107         snprintf(filename, sizeof(filename), "%s%s-f%02d%s",
108                 LOCAL_DUMP_PREFIX, timestamp, frame % 100, LOCAL_DUMP_SUFFIX);
109         return filename;
110 }
111
112 }  // namespace
113
114 Mixer::Mixer(const QSurfaceFormat &format, unsigned num_cards)
115         : httpd(WIDTH, HEIGHT),
116           num_cards(num_cards),
117           mixer_surface(create_surface(format)),
118           h264_encoder_surface(create_surface(format)),
119           correlation(OUTPUT_FREQUENCY),
120           level_compressor(OUTPUT_FREQUENCY),
121           limiter(OUTPUT_FREQUENCY),
122           compressor(OUTPUT_FREQUENCY)
123 {
124         httpd.open_output_file(generate_local_dump_filename(/*frame=*/0).c_str());
125         httpd.start(9095);
126
127         CHECK(init_movit(MOVIT_SHADER_DIR, MOVIT_DEBUG_OFF));
128         check_error();
129
130         // Since we allow non-bouncing 4:2:2 YCbCrInputs, effective subpixel precision
131         // will be halved when sampling them, and we need to compensate here.
132         movit_texel_subpixel_precision /= 2.0;
133
134         resource_pool.reset(new ResourcePool);
135         theme.reset(new Theme("theme.lua", resource_pool.get(), num_cards));
136         for (unsigned i = 0; i < NUM_OUTPUTS; ++i) {
137                 output_channel[i].parent = this;
138         }
139
140         ImageFormat inout_format;
141         inout_format.color_space = COLORSPACE_sRGB;
142         inout_format.gamma_curve = GAMMA_sRGB;
143
144         // Display chain; shows the live output produced by the main chain (its RGBA version).
145         display_chain.reset(new EffectChain(WIDTH, HEIGHT, resource_pool.get()));
146         check_error();
147         display_input = new FlatInput(inout_format, FORMAT_RGB, GL_UNSIGNED_BYTE, WIDTH, HEIGHT);  // FIXME: GL_UNSIGNED_BYTE is really wrong.
148         display_chain->add_input(display_input);
149         display_chain->add_output(inout_format, OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED);
150         display_chain->set_dither_bits(0);  // Don't bother.
151         display_chain->finalize();
152
153         h264_encoder.reset(new H264Encoder(h264_encoder_surface, global_flags.va_display, WIDTH, HEIGHT, &httpd));
154
155         // First try initializing the PCI devices, then USB, until we have the desired number of cards.
156         unsigned num_pci_devices = 0, num_usb_devices = 0;
157         unsigned card_index = 0;
158
159         IDeckLinkIterator *decklink_iterator = CreateDeckLinkIteratorInstance();
160         if (decklink_iterator != nullptr) {
161                 for ( ; card_index < num_cards; ++card_index) {
162                         IDeckLink *decklink;
163                         if (decklink_iterator->Next(&decklink) != S_OK) {
164                                 break;
165                         }
166
167                         configure_card(card_index, format, new DeckLinkCapture(decklink, card_index));
168                         ++num_pci_devices;
169                 }
170                 decklink_iterator->Release();
171                 fprintf(stderr, "Found %d DeckLink PCI card(s).\n", num_pci_devices);
172         } else {
173                 fprintf(stderr, "DeckLink drivers not found. Probing for USB cards only.\n");
174         }
175         for ( ; card_index < num_cards; ++card_index) {
176                 configure_card(card_index, format, new BMUSBCapture(card_index - num_pci_devices));
177                 ++num_usb_devices;
178         }
179
180         if (num_usb_devices > 0) {
181                 BMUSBCapture::start_bm_thread();
182         }
183
184         for (card_index = 0; card_index < num_cards; ++card_index) {
185                 cards[card_index].capture->start_bm_capture();
186         }
187
188         // Set up stuff for NV12 conversion.
189
190         // Cb/Cr shader.
191         string cbcr_vert_shader =
192                 "#version 130 \n"
193                 " \n"
194                 "in vec2 position; \n"
195                 "in vec2 texcoord; \n"
196                 "out vec2 tc0; \n"
197                 "uniform vec2 foo_chroma_offset_0; \n"
198                 " \n"
199                 "void main() \n"
200                 "{ \n"
201                 "    // The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is: \n"
202                 "    // \n"
203                 "    //   2.000  0.000  0.000 -1.000 \n"
204                 "    //   0.000  2.000  0.000 -1.000 \n"
205                 "    //   0.000  0.000 -2.000 -1.000 \n"
206                 "    //   0.000  0.000  0.000  1.000 \n"
207                 "    gl_Position = vec4(2.0 * position.x - 1.0, 2.0 * position.y - 1.0, -1.0, 1.0); \n"
208                 "    vec2 flipped_tc = texcoord; \n"
209                 "    tc0 = flipped_tc + foo_chroma_offset_0; \n"
210                 "} \n";
211         string cbcr_frag_shader =
212                 "#version 130 \n"
213                 "in vec2 tc0; \n"
214                 "uniform sampler2D cbcr_tex; \n"
215                 "out vec4 FragColor; \n"
216                 "void main() { \n"
217                 "    FragColor = texture(cbcr_tex, tc0); \n"
218                 "} \n";
219         vector<string> frag_shader_outputs;
220         cbcr_program_num = resource_pool->compile_glsl_program(cbcr_vert_shader, cbcr_frag_shader, frag_shader_outputs);
221
222         float vertices[] = {
223                 0.0f, 2.0f,
224                 0.0f, 0.0f,
225                 2.0f, 0.0f
226         };
227         cbcr_vbo = generate_vbo(2, GL_FLOAT, sizeof(vertices), vertices);
228         cbcr_position_attribute_index = glGetAttribLocation(cbcr_program_num, "position");
229         cbcr_texcoord_attribute_index = glGetAttribLocation(cbcr_program_num, "texcoord");
230
231         r128.init(2, OUTPUT_FREQUENCY);
232         r128.integr_start();
233
234         locut.init(FILTER_HPF, 2);
235
236         // hlen=16 is pretty low quality, but we use quite a bit of CPU otherwise,
237         // and there's a limit to how important the peak meter is.
238         peak_resampler.setup(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY * 4, /*num_channels=*/2, /*hlen=*/16, /*frel=*/1.0);
239
240         alsa.reset(new ALSAOutput(OUTPUT_FREQUENCY, /*num_channels=*/2));
241 }
242
243 Mixer::~Mixer()
244 {
245         resource_pool->release_glsl_program(cbcr_program_num);
246         glDeleteBuffers(1, &cbcr_vbo);
247         BMUSBCapture::stop_bm_thread();
248
249         for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
250                 {
251                         unique_lock<mutex> lock(bmusb_mutex);
252                         cards[card_index].should_quit = true;  // Unblock thread.
253                         cards[card_index].new_data_ready_changed.notify_all();
254                 }
255                 cards[card_index].capture->stop_dequeue_thread();
256         }
257
258         h264_encoder.reset(nullptr);
259 }
260
261 void Mixer::configure_card(unsigned card_index, const QSurfaceFormat &format, CaptureInterface *capture)
262 {
263         printf("Configuring card %d...\n", card_index);
264
265         CaptureCard *card = &cards[card_index];
266         card->capture = capture;
267         card->capture->set_frame_callback(bind(&Mixer::bm_frame, this, card_index, _1, _2, _3, _4, _5, _6, _7));
268         card->frame_allocator.reset(new PBOFrameAllocator(8 << 20, WIDTH, HEIGHT));  // 8 MB.
269         card->capture->set_video_frame_allocator(card->frame_allocator.get());
270         card->surface = create_surface(format);
271         card->capture->set_dequeue_thread_callbacks(
272                 [card]{
273                         eglBindAPI(EGL_OPENGL_API);
274                         card->context = create_context(card->surface);
275                         if (!make_current(card->context, card->surface)) {
276                                 printf("failed to create bmusb context\n");
277                                 exit(1);
278                         }
279                 },
280                 [this]{
281                         resource_pool->clean_context();
282                 });
283         card->resampling_queue.reset(new ResamplingQueue(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY, 2));
284         card->capture->configure_card();
285 }
286
287
288 namespace {
289
290 int unwrap_timecode(uint16_t current_wrapped, int last)
291 {
292         uint16_t last_wrapped = last & 0xffff;
293         if (current_wrapped > last_wrapped) {
294                 return (last & ~0xffff) | current_wrapped;
295         } else {
296                 return 0x10000 + ((last & ~0xffff) | current_wrapped);
297         }
298 }
299
300 float find_peak(const float *samples, size_t num_samples)
301 {
302         float m = fabs(samples[0]);
303         for (size_t i = 1; i < num_samples; ++i) {
304                 m = max(m, fabs(samples[i]));
305         }
306         return m;
307 }
308
309 void deinterleave_samples(const vector<float> &in, vector<float> *out_l, vector<float> *out_r)
310 {
311         size_t num_samples = in.size() / 2;
312         out_l->resize(num_samples);
313         out_r->resize(num_samples);
314
315         const float *inptr = in.data();
316         float *lptr = &(*out_l)[0];
317         float *rptr = &(*out_r)[0];
318         for (size_t i = 0; i < num_samples; ++i) {
319                 *lptr++ = *inptr++;
320                 *rptr++ = *inptr++;
321         }
322 }
323
324 }  // namespace
325
326 void Mixer::bm_frame(unsigned card_index, uint16_t timecode,
327                      FrameAllocator::Frame video_frame, size_t video_offset, VideoFormat video_format,
328                      FrameAllocator::Frame audio_frame, size_t audio_offset, AudioFormat audio_format)
329 {
330         CaptureCard *card = &cards[card_index];
331
332         if (is_mode_scanning[card_index]) {
333                 if (video_format.has_signal) {
334                         // Found a stable signal, so stop scanning.
335                         is_mode_scanning[card_index] = false;
336                 } else {
337                         static constexpr double switch_time_s = 0.5;  // Should be enough time for the signal to stabilize.
338                         timespec now;
339                         clock_gettime(CLOCK_MONOTONIC, &now);
340                         double sec_since_last_switch = (now.tv_sec - last_mode_scan_change[card_index].tv_sec) +
341                                 1e-9 * (now.tv_nsec - last_mode_scan_change[card_index].tv_nsec);
342                         if (sec_since_last_switch > switch_time_s) {
343                                 // It isn't this mode; try the next one.
344                                 mode_scanlist_index[card_index]++;
345                                 mode_scanlist_index[card_index] %= mode_scanlist[card_index].size();
346                                 cards[card_index].capture->set_video_mode(mode_scanlist[card_index][mode_scanlist_index[card_index]]);
347                                 last_mode_scan_change[card_index] = now;
348                         }
349                 }
350         }
351
352         int64_t frame_length = int64_t(TIMEBASE * video_format.frame_rate_den) / video_format.frame_rate_nom;
353
354         size_t num_samples = (audio_frame.len > audio_offset) ? (audio_frame.len - audio_offset) / audio_format.num_channels / (audio_format.bits_per_sample / 8) : 0;
355         if (num_samples > OUTPUT_FREQUENCY / 10) {
356                 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",
357                         card_index, int(audio_frame.len), int(audio_offset),
358                         timecode, int(video_frame.len), int(video_offset), video_format.id);
359                 if (video_frame.owner) {
360                         video_frame.owner->release_frame(video_frame);
361                 }
362                 if (audio_frame.owner) {
363                         audio_frame.owner->release_frame(audio_frame);
364                 }
365                 return;
366         }
367
368         int64_t local_pts = card->next_local_pts;
369         int dropped_frames = 0;
370         if (card->last_timecode != -1) {
371                 dropped_frames = unwrap_timecode(timecode, card->last_timecode) - card->last_timecode - 1;
372         }
373
374         // Convert the audio to stereo fp32 and add it.
375         vector<float> audio;
376         audio.resize(num_samples * 2);
377         switch (audio_format.bits_per_sample) {
378         case 0:
379                 assert(num_samples == 0);
380                 break;
381         case 24:
382                 convert_fixed24_to_fp32(&audio[0], 2, audio_frame.data + audio_offset, audio_format.num_channels, num_samples);
383                 break;
384         case 32:
385                 convert_fixed32_to_fp32(&audio[0], 2, audio_frame.data + audio_offset, audio_format.num_channels, num_samples);
386                 break;
387         default:
388                 fprintf(stderr, "Cannot handle audio with %u bits per sample\n", audio_format.bits_per_sample);
389                 assert(false);
390         }
391
392         // Add the audio.
393         {
394                 unique_lock<mutex> lock(card->audio_mutex);
395
396                 // Number of samples per frame if we need to insert silence.
397                 // (Could be nonintegral, but resampling will save us then.)
398                 int silence_samples = OUTPUT_FREQUENCY * video_format.frame_rate_den / video_format.frame_rate_nom;
399
400                 if (dropped_frames > MAX_FPS * 2) {
401                         fprintf(stderr, "Card %d lost more than two seconds (or time code jumping around; from 0x%04x to 0x%04x), resetting resampler\n",
402                                 card_index, card->last_timecode, timecode);
403                         card->resampling_queue.reset(new ResamplingQueue(OUTPUT_FREQUENCY, OUTPUT_FREQUENCY, 2));
404                         dropped_frames = 0;
405                 } else if (dropped_frames > 0) {
406                         // Insert silence as needed.
407                         fprintf(stderr, "Card %d dropped %d frame(s) (before timecode 0x%04x), inserting silence.\n",
408                                 card_index, dropped_frames, timecode);
409                         vector<float> silence(silence_samples * 2, 0.0f);
410                         for (int i = 0; i < dropped_frames; ++i) {
411                                 card->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), silence.data(), silence_samples);
412                                 // Note that if the format changed in the meantime, we have
413                                 // no way of detecting that; we just have to assume the frame length
414                                 // is always the same.
415                                 local_pts += frame_length;
416                         }
417                 }
418                 if (num_samples == 0) {
419                         audio.resize(silence_samples * 2);
420                         num_samples = silence_samples;
421                 }
422                 card->resampling_queue->add_input_samples(local_pts / double(TIMEBASE), audio.data(), num_samples);
423                 card->next_local_pts = local_pts + frame_length;
424         }
425
426         card->last_timecode = timecode;
427
428         // Done with the audio, so release it.
429         if (audio_frame.owner) {
430                 audio_frame.owner->release_frame(audio_frame);
431         }
432
433         {
434                 // Wait until the previous frame was consumed.
435                 unique_lock<mutex> lock(bmusb_mutex);
436                 card->new_data_ready_changed.wait(lock, [card]{ return !card->new_data_ready || card->should_quit; });
437                 if (card->should_quit) return;
438         }
439
440         size_t expected_length = video_format.width * (video_format.height + video_format.extra_lines_top + video_format.extra_lines_bottom) * 2;
441         if (video_frame.len - video_offset == 0 ||
442             video_frame.len - video_offset != expected_length) {
443                 if (video_frame.len != 0) {
444                         printf("Card %d: Dropping video frame with wrong length (%ld; expected %ld)\n",
445                                 card_index, video_frame.len - video_offset, expected_length);
446                 }
447                 if (video_frame.owner) {
448                         video_frame.owner->release_frame(video_frame);
449                 }
450
451                 // Still send on the information that we _had_ a frame, even though it's corrupted,
452                 // so that pts can go up accordingly.
453                 {
454                         unique_lock<mutex> lock(bmusb_mutex);
455                         card->new_data_ready = true;
456                         card->new_frame = RefCountedFrame(FrameAllocator::Frame());
457                         card->new_frame_length = frame_length;
458                         card->new_frame_interlaced = false;
459                         card->new_data_ready_fence = nullptr;
460                         card->dropped_frames = dropped_frames;
461                         card->new_data_ready_changed.notify_all();
462                 }
463                 return;
464         }
465
466         PBOFrameAllocator::Userdata *userdata = (PBOFrameAllocator::Userdata *)video_frame.userdata;
467
468         unsigned num_fields = video_format.interlaced ? 2 : 1;
469         timespec frame_upload_start;
470         if (video_format.interlaced) {
471                 // Send the two fields along as separate frames; the other side will need to add
472                 // a deinterlacer to actually get this right.
473                 assert(video_format.height % 2 == 0);
474                 video_format.height /= 2;
475                 assert(frame_length % 2 == 0);
476                 frame_length /= 2;
477                 num_fields = 2;
478                 clock_gettime(CLOCK_MONOTONIC, &frame_upload_start);
479         }
480         userdata->last_interlaced = video_format.interlaced;
481         userdata->last_has_signal = video_format.has_signal;
482         userdata->last_frame_rate_nom = video_format.frame_rate_nom;
483         userdata->last_frame_rate_den = video_format.frame_rate_den;
484         RefCountedFrame new_frame(video_frame);
485
486         // Upload the textures.
487         size_t cbcr_width = video_format.width / 2;
488         size_t cbcr_offset = video_offset / 2;
489         size_t y_offset = video_frame.size / 2 + video_offset / 2;
490
491         for (unsigned field = 0; field < num_fields; ++field) {
492                 unsigned field_start_line = (field == 1) ? video_format.second_field_start : video_format.extra_lines_top + field * (video_format.height + 22);
493
494                 if (userdata->tex_y[field] == 0 ||
495                     userdata->tex_cbcr[field] == 0 ||
496                     video_format.width != userdata->last_width[field] ||
497                     video_format.height != userdata->last_height[field]) {
498                         // We changed resolution since last use of this texture, so we need to create
499                         // a new object. Note that this each card has its own PBOFrameAllocator,
500                         // we don't need to worry about these flip-flopping between resolutions.
501                         glBindTexture(GL_TEXTURE_2D, userdata->tex_cbcr[field]);
502                         check_error();
503                         glTexImage2D(GL_TEXTURE_2D, 0, GL_RG8, cbcr_width, video_format.height, 0, GL_RG, GL_UNSIGNED_BYTE, nullptr);
504                         check_error();
505                         glBindTexture(GL_TEXTURE_2D, userdata->tex_y[field]);
506                         check_error();
507                         glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, video_format.width, video_format.height, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr);
508                         check_error();
509                         userdata->last_width[field] = video_format.width;
510                         userdata->last_height[field] = video_format.height;
511                 }
512
513                 GLuint pbo = userdata->pbo;
514                 check_error();
515                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
516                 check_error();
517                 glMemoryBarrier(GL_CLIENT_MAPPED_BUFFER_BARRIER_BIT);
518                 check_error();
519
520                 glBindTexture(GL_TEXTURE_2D, userdata->tex_cbcr[field]);
521                 check_error();
522                 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, cbcr_width, video_format.height, GL_RG, GL_UNSIGNED_BYTE, BUFFER_OFFSET(cbcr_offset + cbcr_width * field_start_line * sizeof(uint16_t)));
523                 check_error();
524                 glBindTexture(GL_TEXTURE_2D, userdata->tex_y[field]);
525                 check_error();
526                 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, video_format.width, video_format.height, GL_RED, GL_UNSIGNED_BYTE, BUFFER_OFFSET(y_offset + video_format.width * field_start_line));
527                 check_error();
528                 glBindTexture(GL_TEXTURE_2D, 0);
529                 check_error();
530                 glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
531                 check_error();
532                 GLsync fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, /*flags=*/0);
533                 check_error();
534                 assert(fence != nullptr);
535
536                 if (field == 1) {
537                         // Don't upload the second field as fast as we can; wait until
538                         // the field time has approximately passed. (Otherwise, we could
539                         // get timing jitter against the other sources, and possibly also
540                         // against the video display, although the latter is not as critical.)
541                         // This requires our system clock to be reasonably close to the
542                         // video clock, but that's not an unreasonable assumption.
543                         timespec second_field_start;
544                         second_field_start.tv_nsec = frame_upload_start.tv_nsec +
545                                 frame_length * 1000000000 / TIMEBASE;
546                         second_field_start.tv_sec = frame_upload_start.tv_sec +
547                                 second_field_start.tv_nsec / 1000000000;
548                         second_field_start.tv_nsec %= 1000000000;
549
550                         while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME,
551                                                &second_field_start, nullptr) == -1 &&
552                                errno == EINTR) ;
553                 }
554
555                 {
556                         unique_lock<mutex> lock(bmusb_mutex);
557                         card->new_data_ready = true;
558                         card->new_frame = new_frame;
559                         card->new_frame_length = frame_length;
560                         card->new_frame_field = field;
561                         card->new_frame_interlaced = video_format.interlaced;
562                         card->new_data_ready_fence = fence;
563                         card->dropped_frames = dropped_frames;
564                         card->new_data_ready_changed.notify_all();
565
566                         if (field != num_fields - 1) {
567                                 // Wait until the previous frame was consumed.
568                                 card->new_data_ready_changed.wait(lock, [card]{ return !card->new_data_ready || card->should_quit; });
569                                 if (card->should_quit) return;
570                         }
571                 }
572         }
573 }
574
575 void Mixer::thread_func()
576 {
577         eglBindAPI(EGL_OPENGL_API);
578         QOpenGLContext *context = create_context(mixer_surface);
579         if (!make_current(context, mixer_surface)) {
580                 printf("oops\n");
581                 exit(1);
582         }
583
584         struct timespec start, now;
585         clock_gettime(CLOCK_MONOTONIC, &start);
586
587         int frame = 0;
588         int stats_dropped_frames = 0;
589
590         while (!should_quit) {
591                 CaptureCard card_copy[MAX_CARDS];
592                 int num_samples[MAX_CARDS];
593
594                 {
595                         unique_lock<mutex> lock(bmusb_mutex);
596
597                         // The first card is the master timer, so wait for it to have a new frame.
598                         // TODO: Make configurable, and with a timeout.
599                         cards[0].new_data_ready_changed.wait(lock, [this]{ return cards[0].new_data_ready; });
600
601                         for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
602                                 CaptureCard *card = &cards[card_index];
603                                 card_copy[card_index].new_data_ready = card->new_data_ready;
604                                 card_copy[card_index].new_frame = card->new_frame;
605                                 card_copy[card_index].new_frame_length = card->new_frame_length;
606                                 card_copy[card_index].new_frame_field = card->new_frame_field;
607                                 card_copy[card_index].new_frame_interlaced = card->new_frame_interlaced;
608                                 card_copy[card_index].new_data_ready_fence = card->new_data_ready_fence;
609                                 card_copy[card_index].dropped_frames = card->dropped_frames;
610                                 card->new_data_ready = false;
611                                 card->new_data_ready_changed.notify_all();
612
613                                 int num_samples_times_timebase = OUTPUT_FREQUENCY * card->new_frame_length + card->fractional_samples;
614                                 num_samples[card_index] = num_samples_times_timebase / TIMEBASE;
615                                 card->fractional_samples = num_samples_times_timebase % TIMEBASE;
616                                 assert(num_samples[card_index] >= 0);
617                         }
618                 }
619
620                 // Resample the audio as needed, including from previously dropped frames.
621                 assert(num_cards > 0);
622                 for (unsigned frame_num = 0; frame_num < card_copy[0].dropped_frames + 1; ++frame_num) {
623                         {
624                                 // Signal to the audio thread to process this frame.
625                                 unique_lock<mutex> lock(audio_mutex);
626                                 audio_task_queue.push(AudioTask{pts_int, num_samples[0]});
627                                 audio_task_queue_changed.notify_one();
628                         }
629                         if (frame_num != card_copy[0].dropped_frames) {
630                                 // For dropped frames, increase the pts. Note that if the format changed
631                                 // in the meantime, we have no way of detecting that; we just have to
632                                 // assume the frame length is always the same.
633                                 ++stats_dropped_frames;
634                                 pts_int += card_copy[0].new_frame_length;
635                         }
636                 }
637
638                 if (audio_level_callback != nullptr) {
639                         unique_lock<mutex> lock(compressor_mutex);
640                         double loudness_s = r128.loudness_S();
641                         double loudness_i = r128.integrated();
642                         double loudness_range_low = r128.range_min();
643                         double loudness_range_high = r128.range_max();
644
645                         audio_level_callback(loudness_s, 20.0 * log10(peak),
646                                              loudness_i, loudness_range_low, loudness_range_high,
647                                              gain_staging_db, 20.0 * log10(final_makeup_gain),
648                                              correlation.get_correlation());
649                 }
650
651                 for (unsigned card_index = 1; card_index < num_cards; ++card_index) {
652                         if (card_copy[card_index].new_data_ready && card_copy[card_index].new_frame->len == 0) {
653                                 ++card_copy[card_index].dropped_frames;
654                         }
655                         if (card_copy[card_index].dropped_frames > 0) {
656                                 printf("Card %u dropped %d frames before this\n",
657                                         card_index, int(card_copy[card_index].dropped_frames));
658                         }
659                 }
660
661                 // If the first card is reporting a corrupted or otherwise dropped frame,
662                 // just increase the pts (skipping over this frame) and don't try to compute anything new.
663                 if (card_copy[0].new_frame->len == 0) {
664                         ++stats_dropped_frames;
665                         pts_int += card_copy[0].new_frame_length;
666                         continue;
667                 }
668
669                 for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
670                         CaptureCard *card = &card_copy[card_index];
671                         if (!card->new_data_ready || card->new_frame->len == 0)
672                                 continue;
673
674                         assert(card->new_frame != nullptr);
675                         insert_new_frame(card->new_frame, card->new_frame_field, card->new_frame_interlaced, card_index, &input_state);
676                         check_error();
677
678                         // The new texture might still be uploaded,
679                         // tell the GPU to wait until it's there.
680                         if (card->new_data_ready_fence) {
681                                 glWaitSync(card->new_data_ready_fence, /*flags=*/0, GL_TIMEOUT_IGNORED);
682                                 check_error();
683                                 glDeleteSync(card->new_data_ready_fence);
684                                 check_error();
685                         }
686                 }
687
688                 // Get the main chain from the theme, and set its state immediately.
689                 Theme::Chain theme_main_chain = theme->get_chain(0, pts(), WIDTH, HEIGHT, input_state);
690                 EffectChain *chain = theme_main_chain.chain;
691                 theme_main_chain.setup_chain();
692                 //theme_main_chain.chain->enable_phase_timing(true);
693
694                 GLuint y_tex, cbcr_tex;
695                 bool got_frame = h264_encoder->begin_frame(&y_tex, &cbcr_tex);
696                 assert(got_frame);
697
698                 // Render main chain.
699                 GLuint cbcr_full_tex = resource_pool->create_2d_texture(GL_RG8, WIDTH, HEIGHT);
700                 GLuint rgba_tex = resource_pool->create_2d_texture(GL_RGB565, WIDTH, HEIGHT);  // Saves texture bandwidth, although dithering gets messed up.
701                 GLuint fbo = resource_pool->create_fbo(y_tex, cbcr_full_tex, rgba_tex);
702                 check_error();
703                 chain->render_to_fbo(fbo, WIDTH, HEIGHT);
704                 resource_pool->release_fbo(fbo);
705
706                 subsample_chroma(cbcr_full_tex, cbcr_tex);
707                 resource_pool->release_2d_texture(cbcr_full_tex);
708
709                 // Set the right state for rgba_tex.
710                 glBindFramebuffer(GL_FRAMEBUFFER, 0);
711                 glBindTexture(GL_TEXTURE_2D, rgba_tex);
712                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
713                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
714                 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
715
716                 RefCountedGLsync fence(GL_SYNC_GPU_COMMANDS_COMPLETE, /*flags=*/0);
717                 check_error();
718
719                 const int64_t av_delay = TIMEBASE / 10;  // Corresponds to the fixed delay in resampling_queue.h. TODO: Make less hard-coded.
720                 h264_encoder->end_frame(fence, pts_int + av_delay, theme_main_chain.input_frames);
721                 ++frame;
722                 pts_int += card_copy[0].new_frame_length;
723
724                 // The live frame just shows the RGBA texture we just rendered.
725                 // It owns rgba_tex now.
726                 DisplayFrame live_frame;
727                 live_frame.chain = display_chain.get();
728                 live_frame.setup_chain = [this, rgba_tex]{
729                         display_input->set_texture_num(rgba_tex);
730                 };
731                 live_frame.ready_fence = fence;
732                 live_frame.input_frames = {};
733                 live_frame.temp_textures = { rgba_tex };
734                 output_channel[OUTPUT_LIVE].output_frame(live_frame);
735
736                 // Set up preview and any additional channels.
737                 for (int i = 1; i < theme->get_num_channels() + 2; ++i) {
738                         DisplayFrame display_frame;
739                         Theme::Chain chain = theme->get_chain(i, pts(), WIDTH, HEIGHT, input_state);  // FIXME: dimensions
740                         display_frame.chain = chain.chain;
741                         display_frame.setup_chain = chain.setup_chain;
742                         display_frame.ready_fence = fence;
743                         display_frame.input_frames = chain.input_frames;
744                         display_frame.temp_textures = {};
745                         output_channel[i].output_frame(display_frame);
746                 }
747
748                 clock_gettime(CLOCK_MONOTONIC, &now);
749                 double elapsed = now.tv_sec - start.tv_sec +
750                         1e-9 * (now.tv_nsec - start.tv_nsec);
751                 if (frame % 100 == 0) {
752                         printf("%d frames (%d dropped) in %.3f seconds = %.1f fps (%.1f ms/frame)\n",
753                                 frame, stats_dropped_frames, elapsed, frame / elapsed,
754                                 1e3 * elapsed / frame);
755                 //      chain->print_phase_timing();
756                 }
757
758                 if (should_cut.exchange(false)) {  // Test and clear.
759                         string filename = generate_local_dump_filename(frame);
760                         printf("Starting new recording: %s\n", filename.c_str());
761                         h264_encoder->shutdown();
762                         httpd.close_output_file();
763                         httpd.open_output_file(filename.c_str());
764                         h264_encoder.reset(new H264Encoder(h264_encoder_surface, global_flags.va_display, WIDTH, HEIGHT, &httpd));
765                 }
766
767 #if 0
768                 // Reset every 100 frames, so that local variations in frame times
769                 // (especially for the first few frames, when the shaders are
770                 // compiled etc.) don't make it hard to measure for the entire
771                 // remaining duration of the program.
772                 if (frame == 10000) {
773                         frame = 0;
774                         start = now;
775                 }
776 #endif
777                 check_error();
778         }
779
780         resource_pool->clean_context();
781 }
782
783 void Mixer::audio_thread_func()
784 {
785         while (!should_quit) {
786                 AudioTask task;
787
788                 {
789                         unique_lock<mutex> lock(audio_mutex);
790                         audio_task_queue_changed.wait(lock, [this]{ return !audio_task_queue.empty(); });
791                         task = audio_task_queue.front();
792                         audio_task_queue.pop();
793                 }
794
795                 process_audio_one_frame(task.pts_int, task.num_samples);
796         }
797 }
798
799 void Mixer::process_audio_one_frame(int64_t frame_pts_int, int num_samples)
800 {
801         vector<float> samples_card;
802         vector<float> samples_out;
803
804         // TODO: Allow mixing audio from several sources.
805         unsigned selected_audio_card = theme->map_signal(audio_source_channel);
806         assert(selected_audio_card < num_cards);
807
808         for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
809                 samples_card.resize(num_samples * 2);
810                 {
811                         unique_lock<mutex> lock(cards[card_index].audio_mutex);
812                         if (!cards[card_index].resampling_queue->get_output_samples(double(frame_pts_int) / TIMEBASE, &samples_card[0], num_samples)) {
813                                 printf("Card %d reported previous underrun.\n", card_index);
814                         }
815                 }
816                 if (card_index == selected_audio_card) {
817                         samples_out = move(samples_card);
818                 }
819         }
820
821         // Cut away everything under 120 Hz (or whatever the cutoff is);
822         // we don't need it for voice, and it will reduce headroom
823         // and confuse the compressor. (In particular, any hums at 50 or 60 Hz
824         // should be dampened.)
825         if (locut_enabled) {
826                 locut.render(samples_out.data(), samples_out.size() / 2, locut_cutoff_hz * 2.0 * M_PI / OUTPUT_FREQUENCY, 0.5f);
827         }
828
829         // Apply a level compressor to get the general level right.
830         // Basically, if it's over about -40 dBFS, we squeeze it down to that level
831         // (or more precisely, near it, since we don't use infinite ratio),
832         // then apply a makeup gain to get it to -14 dBFS. -14 dBFS is, of course,
833         // entirely arbitrary, but from practical tests with speech, it seems to
834         // put ut around -23 LUFS, so it's a reasonable starting point for later use.
835         {
836                 unique_lock<mutex> lock(compressor_mutex);
837                 if (level_compressor_enabled) {
838                         float threshold = 0.01f;   // -40 dBFS.
839                         float ratio = 20.0f;
840                         float attack_time = 0.5f;
841                         float release_time = 20.0f;
842                         float makeup_gain = pow(10.0f, (ref_level_dbfs - (-40.0f)) / 20.0f);  // +26 dB.
843                         level_compressor.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
844                         gain_staging_db = 20.0 * log10(level_compressor.get_attenuation() * makeup_gain);
845                 } else {
846                         // Just apply the gain we already had.
847                         float g = pow(10.0f, gain_staging_db / 20.0f);
848                         for (size_t i = 0; i < samples_out.size(); ++i) {
849                                 samples_out[i] *= g;
850                         }
851                 }
852         }
853
854 #if 0
855         printf("level=%f (%+5.2f dBFS) attenuation=%f (%+5.2f dB) end_result=%+5.2f dB\n",
856                 level_compressor.get_level(), 20.0 * log10(level_compressor.get_level()),
857                 level_compressor.get_attenuation(), 20.0 * log10(level_compressor.get_attenuation()),
858                 20.0 * log10(level_compressor.get_level() * level_compressor.get_attenuation() * makeup_gain));
859 #endif
860
861 //      float limiter_att, compressor_att;
862
863         // The real compressor.
864         if (compressor_enabled) {
865                 float threshold = pow(10.0f, compressor_threshold_dbfs / 20.0f);
866                 float ratio = 20.0f;
867                 float attack_time = 0.005f;
868                 float release_time = 0.040f;
869                 float makeup_gain = 2.0f;  // +6 dB.
870                 compressor.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
871 //              compressor_att = compressor.get_attenuation();
872         }
873
874         // Finally a limiter at -4 dB (so, -10 dBFS) to take out the worst peaks only.
875         // Note that since ratio is not infinite, we could go slightly higher than this.
876         if (limiter_enabled) {
877                 float threshold = pow(10.0f, limiter_threshold_dbfs / 20.0f);
878                 float ratio = 30.0f;
879                 float attack_time = 0.0f;  // Instant.
880                 float release_time = 0.020f;
881                 float makeup_gain = 1.0f;  // 0 dB.
882                 limiter.process(samples_out.data(), samples_out.size() / 2, threshold, ratio, attack_time, release_time, makeup_gain);
883 //              limiter_att = limiter.get_attenuation();
884         }
885
886 //      printf("limiter=%+5.1f  compressor=%+5.1f\n", 20.0*log10(limiter_att), 20.0*log10(compressor_att));
887
888         // Upsample 4x to find interpolated peak.
889         peak_resampler.inp_data = samples_out.data();
890         peak_resampler.inp_count = samples_out.size() / 2;
891
892         vector<float> interpolated_samples_out;
893         interpolated_samples_out.resize(samples_out.size());
894         while (peak_resampler.inp_count > 0) {  // About four iterations.
895                 peak_resampler.out_data = &interpolated_samples_out[0];
896                 peak_resampler.out_count = interpolated_samples_out.size() / 2;
897                 peak_resampler.process();
898                 size_t out_stereo_samples = interpolated_samples_out.size() / 2 - peak_resampler.out_count;
899                 peak = max<float>(peak, find_peak(interpolated_samples_out.data(), out_stereo_samples * 2));
900                 peak_resampler.out_data = nullptr;
901         }
902
903         // At this point, we are most likely close to +0 LU, but all of our
904         // measurements have been on raw sample values, not R128 values.
905         // So we have a final makeup gain to get us to +0 LU; the gain
906         // adjustments required should be relatively small, and also, the
907         // offset shouldn't change much (only if the type of audio changes
908         // significantly). Thus, we shoot for updating this value basically
909         // “whenever we process buffers”, since the R128 calculation isn't exactly
910         // something we get out per-sample.
911         //
912         // Note that there's a feedback loop here, so we choose a very slow filter
913         // (half-time of 100 seconds).
914         double target_loudness_factor, alpha;
915         {
916                 unique_lock<mutex> lock(compressor_mutex);
917                 double loudness_lu = r128.loudness_M() - ref_level_lufs;
918                 double current_makeup_lu = 20.0f * log10(final_makeup_gain);
919                 target_loudness_factor = pow(10.0f, -loudness_lu / 20.0f);
920
921                 // If we're outside +/- 5 LU uncorrected, we don't count it as
922                 // a normal signal (probably silence) and don't change the
923                 // correction factor; just apply what we already have.
924                 if (fabs(loudness_lu - current_makeup_lu) >= 5.0 || !final_makeup_gain_auto) {
925                         alpha = 0.0;
926                 } else {
927                         // Formula adapted from
928                         // https://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filter.
929                         const double half_time_s = 100.0;
930                         const double fc_mul_2pi_delta_t = 1.0 / (half_time_s * OUTPUT_FREQUENCY);
931                         alpha = fc_mul_2pi_delta_t / (fc_mul_2pi_delta_t + 1.0);
932                 }
933
934                 double m = final_makeup_gain;
935                 for (size_t i = 0; i < samples_out.size(); i += 2) {
936                         samples_out[i + 0] *= m;
937                         samples_out[i + 1] *= m;
938                         m += (target_loudness_factor - m) * alpha;
939                 }
940                 final_makeup_gain = m;
941         }
942
943         // Find R128 levels and L/R correlation.
944         vector<float> left, right;
945         deinterleave_samples(samples_out, &left, &right);
946         float *ptrs[] = { left.data(), right.data() };
947         {
948                 unique_lock<mutex> lock(compressor_mutex);
949                 r128.process(left.size(), ptrs);
950                 correlation.process_samples(samples_out);
951         }
952
953         // Send the samples to the sound card.
954         if (alsa) {
955                 alsa->write(samples_out);
956         }
957
958         // And finally add them to the output.
959         h264_encoder->add_audio(frame_pts_int, move(samples_out));
960 }
961
962 void Mixer::subsample_chroma(GLuint src_tex, GLuint dst_tex)
963 {
964         GLuint vao;
965         glGenVertexArrays(1, &vao);
966         check_error();
967
968         glBindVertexArray(vao);
969         check_error();
970
971         // Extract Cb/Cr.
972         GLuint fbo = resource_pool->create_fbo(dst_tex);
973         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
974         glViewport(0, 0, WIDTH/2, HEIGHT/2);
975         check_error();
976
977         glUseProgram(cbcr_program_num);
978         check_error();
979
980         glActiveTexture(GL_TEXTURE0);
981         check_error();
982         glBindTexture(GL_TEXTURE_2D, src_tex);
983         check_error();
984         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
985         check_error();
986         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
987         check_error();
988         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
989         check_error();
990
991         float chroma_offset_0[] = { -0.5f / WIDTH, 0.0f };
992         set_uniform_vec2(cbcr_program_num, "foo", "chroma_offset_0", chroma_offset_0);
993
994         glBindBuffer(GL_ARRAY_BUFFER, cbcr_vbo);
995         check_error();
996
997         for (GLint attr_index : { cbcr_position_attribute_index, cbcr_texcoord_attribute_index }) {
998                 glEnableVertexAttribArray(attr_index);
999                 check_error();
1000                 glVertexAttribPointer(attr_index, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
1001                 check_error();
1002         }
1003
1004         glDrawArrays(GL_TRIANGLES, 0, 3);
1005         check_error();
1006
1007         for (GLint attr_index : { cbcr_position_attribute_index, cbcr_texcoord_attribute_index }) {
1008                 glDisableVertexAttribArray(attr_index);
1009                 check_error();
1010         }
1011
1012         glUseProgram(0);
1013         check_error();
1014         glBindFramebuffer(GL_FRAMEBUFFER, 0);
1015         check_error();
1016
1017         resource_pool->release_fbo(fbo);
1018         glDeleteVertexArrays(1, &vao);
1019 }
1020
1021 void Mixer::release_display_frame(DisplayFrame *frame)
1022 {
1023         for (GLuint texnum : frame->temp_textures) {
1024                 resource_pool->release_2d_texture(texnum);
1025         }
1026         frame->temp_textures.clear();
1027         frame->ready_fence.reset();
1028         frame->input_frames.clear();
1029 }
1030
1031 void Mixer::start()
1032 {
1033         mixer_thread = thread(&Mixer::thread_func, this);
1034         audio_thread = thread(&Mixer::audio_thread_func, this);
1035 }
1036
1037 void Mixer::quit()
1038 {
1039         should_quit = true;
1040         mixer_thread.join();
1041         audio_thread.join();
1042 }
1043
1044 void Mixer::transition_clicked(int transition_num)
1045 {
1046         theme->transition_clicked(transition_num, pts());
1047 }
1048
1049 void Mixer::channel_clicked(int preview_num)
1050 {
1051         theme->channel_clicked(preview_num);
1052 }
1053
1054 void Mixer::reset_meters()
1055 {
1056         peak_resampler.reset();
1057         peak = 0.0f;
1058         r128.reset();
1059         r128.integr_start();
1060         correlation.reset();
1061 }
1062
1063 void Mixer::start_mode_scanning(unsigned card_index)
1064 {
1065         assert(card_index < num_cards);
1066         if (is_mode_scanning[card_index]) {
1067                 return;
1068         }
1069         is_mode_scanning[card_index] = true;
1070         mode_scanlist[card_index].clear();
1071         for (const auto &mode : cards[card_index].capture->get_available_video_modes()) {
1072                 mode_scanlist[card_index].push_back(mode.first);
1073         }
1074         assert(!mode_scanlist[card_index].empty());
1075         mode_scanlist_index[card_index] = 0;
1076         cards[card_index].capture->set_video_mode(mode_scanlist[card_index][0]);
1077         clock_gettime(CLOCK_MONOTONIC, &last_mode_scan_change[card_index]);
1078 }
1079
1080 Mixer::OutputChannel::~OutputChannel()
1081 {
1082         if (has_current_frame) {
1083                 parent->release_display_frame(&current_frame);
1084         }
1085         if (has_ready_frame) {
1086                 parent->release_display_frame(&ready_frame);
1087         }
1088 }
1089
1090 void Mixer::OutputChannel::output_frame(DisplayFrame frame)
1091 {
1092         // Store this frame for display. Remove the ready frame if any
1093         // (it was seemingly never used).
1094         {
1095                 unique_lock<mutex> lock(frame_mutex);
1096                 if (has_ready_frame) {
1097                         parent->release_display_frame(&ready_frame);
1098                 }
1099                 ready_frame = frame;
1100                 has_ready_frame = true;
1101         }
1102
1103         if (has_new_frame_ready_callback) {
1104                 new_frame_ready_callback();
1105         }
1106 }
1107
1108 bool Mixer::OutputChannel::get_display_frame(DisplayFrame *frame)
1109 {
1110         unique_lock<mutex> lock(frame_mutex);
1111         if (!has_current_frame && !has_ready_frame) {
1112                 return false;
1113         }
1114
1115         if (has_current_frame && has_ready_frame) {
1116                 // We have a new ready frame. Toss the current one.
1117                 parent->release_display_frame(&current_frame);
1118                 has_current_frame = false;
1119         }
1120         if (has_ready_frame) {
1121                 assert(!has_current_frame);
1122                 current_frame = ready_frame;
1123                 ready_frame.ready_fence.reset();  // Drop the refcount.
1124                 ready_frame.input_frames.clear();  // Drop the refcounts.
1125                 has_current_frame = true;
1126                 has_ready_frame = false;
1127         }
1128
1129         *frame = current_frame;
1130         return true;
1131 }
1132
1133 void Mixer::OutputChannel::set_frame_ready_callback(Mixer::new_frame_ready_callback_t callback)
1134 {
1135         new_frame_ready_callback = callback;
1136         has_new_frame_ready_callback = true;
1137 }