/* * jack output driver. This file is part of Shairport Sync. * Copyright (c) 2019 Mike Brady , * Jörn Nettingsmeier * * All rights reserved. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include "audio.h" #include "common.h" #include #include #include #include #include #include #include // Two-channel, 16bit audio: static const int bytes_per_frame = 4; // Four seconds buffer -- should be plenty #define buffer_size (44100 * 4 * bytes_per_frame) static pthread_mutex_t buffer_mutex = PTHREAD_MUTEX_INITIALIZER; static pthread_mutex_t client_mutex = PTHREAD_MUTEX_INITIALIZER; int jack_init(int, char **); void jack_deinit(void); void jack_start(int, int); int play(void *, int); void jack_stop(void); int jack_delay(long *); void jack_flush(void); audio_output audio_jack = {.name = "jack", .help = NULL, .init = &jack_init, .deinit = &jack_deinit, .prepare = NULL, .start = &jack_start, .stop = NULL, .is_running = NULL, .flush = &jack_flush, .delay = &jack_delay, .play = &play, .volume = NULL, .parameters = NULL, .mute = NULL}; // This also affects deinterlacing. // So make it exactly the number of incoming audio channels! #define NPORTS 2 static jack_port_t *port[NPORTS]; static const char *port_name[NPORTS] = {"out_L", "out_R"}; static jack_client_t *client; static jack_nframes_t sample_rate; static jack_nframes_t jack_latency; static jack_ringbuffer_t *jackbuf; static int flush_please = 0; static jack_latency_range_t latest_latency_range[NPORTS]; static int64_t time_of_latest_transfer; static inline jack_default_audio_sample_t sample_conv(short sample) { // It sounds correct, but I don't understand it. // Zero int needs to be zero float. Check. // Plus 32767 int is 1.0. Check. // Minus 32767 int is -0.99997. And here my brain shuts down. // In my head, it should be 1.0, and we should tolerate an overflow // at minus 32768. But I'm sure there's a textbook explanation somewhere. return ((sample < 0) ? (-1.0 * sample / SHRT_MIN) : (1.0 * sample / SHRT_MAX)); } static void deinterleave_and_convert(const char *interleaved_input_buffer, jack_default_audio_sample_t *jack_output_buffer[], jack_nframes_t offset, jack_nframes_t nframes) { jack_nframes_t f; // We're dealing with 16bit audio here: short *ifp = (short *)interleaved_input_buffer; // Zero-copy, we're working directly on the target and destination buffers, // so deal with an offset for the second part of the input ringbuffer for (f = offset; f < (nframes + offset); f++) { for (int i = 0; i < NPORTS; i++) { jack_output_buffer[i][f] = sample_conv(*ifp++); } } } // This is the JACK process callback. We don't decide when it runs. // It must be hard-realtime safe (i.e. fully deterministic, with constant CPU // usage. No calls to anything that could ever block: no syscalls, no screen // output, no file access, no mutexes... // The JACK ringbuffer we use to get the data in here is explicitly lock-free. static int process(jack_nframes_t nframes, __attribute__((unused)) void *arg) { jack_default_audio_sample_t *buffer[NPORTS]; // Expect an array of two elements because of possible ringbuffer wrap-around: jack_ringbuffer_data_t v[2] = {0}; jack_nframes_t i, thisbuf; int frames_written = 0; int frames_required = 0; for (i = 0; i < NPORTS; i++) { buffer[i] = (jack_default_audio_sample_t *)jack_port_get_buffer(port[i], nframes); } if (flush_please) { // We just move the read pointer ahead without doing anything with the data. jack_ringbuffer_read_advance(jackbuf, jack_ringbuffer_read_space(jackbuf)); flush_please = 0; // Since we don't change nframes, the whole buffer will be zeroed later. } else { jack_ringbuffer_get_read_vector(jackbuf, v); for (i = 0; i < 2; i++) { thisbuf = v[i].len / bytes_per_frame; if (thisbuf > nframes) { frames_required = nframes; } else { frames_required = thisbuf; } deinterleave_and_convert(v[i].buf, buffer, frames_written, frames_required); frames_written += frames_required; nframes -= frames_required; } jack_ringbuffer_read_advance(jackbuf, frames_written * bytes_per_frame); } // If there are any more frames to put into the buffer, fill them with // silence. This is a critical underflow situation. Let's at least keep the JACK // graph humming along while preventing the motorboat sound of a repeating buffer. while (nframes > 0) { for (i = 0; i < NPORTS; i++) { buffer[i][frames_written] = 0.0; } frames_written++; nframes--; } return 0; // Tell JACK that all is well. } // This is the JACK graph reorder callback. Now we know some JACK connections // have changed, so we recompute the latency. static int graph(__attribute__((unused)) void *arg) { int latency = 0; debug(2, "JACK graph reorder callback called."); for (int i = 0; i < NPORTS; i++) { jack_port_get_latency_range(port[i], JackPlaybackLatency, &latest_latency_range[i]); debug(2, "JACK latency for port %s\tmin: %d\t max: %d", port_name[i], latest_latency_range[i].min, latest_latency_range[i].max); latency += latest_latency_range[i].max; } latency /= NPORTS; jack_latency = latency; debug(1, "Average maximum JACK latency across all ports: %d", jack_latency); return 0; } // This the function JACK will call in case of an error in the library. static void error(const char *desc) { warn("JACK error: \"%s\"", desc); } // This is the function JACK will call in case of a non-critical event in the library. static void info(const char *desc) { inform("JACK information: \"%s\"", desc); } int jack_init(__attribute__((unused)) int argc, __attribute__((unused)) char **argv) { int i; config.audio_backend_latency_offset = 0; config.audio_backend_buffer_desired_length = 0.500; // Below this, soxr interpolation will not occur -- it'll be basic interpolation // instead. config.audio_backend_buffer_interpolation_threshold_in_seconds = 0.25; // Do the "general" audio options. Note, these options are in the "general" stanza! parse_general_audio_options(); // Now the options specific to the backend, from the "jack" stanza: if (config.cfg != NULL) { const char *str; if (config_lookup_string(config.cfg, "jack.client_name", &str)) { config.jack_client_name = (char *)str; } if (config_lookup_string(config.cfg, "jack.autoconnect_pattern", &str)) { config.jack_autoconnect_pattern = (char *)str; } } if (config.jack_client_name == NULL) config.jack_client_name = strdup("shairport-sync"); jackbuf = jack_ringbuffer_create(buffer_size); if (jackbuf == NULL) die("Can't allocate %d bytes for the JACK ringbuffer.", buffer_size); // Lock the ringbuffer into memory so that it never gets paged out, which would // break realtime constraints. jack_ringbuffer_mlock(jackbuf); // This mutex should not be necessary, but removing it causes segfaults on // shutdown. Apparently, there are multiple threads in the main program trying // to do stuff. FIXME: Try to consolidate into one thread and get rid of this lock. pthread_mutex_lock(&client_mutex); jack_status_t status; client = jack_client_open(config.jack_client_name, JackNoStartServer, &status); if (!client) { die("Could not start JACK server. JackStatus is %x", status); } sample_rate = jack_get_sample_rate(client); if (sample_rate != 44100) { die("The JACK server is running at the wrong sample rate (%d) for Shairport Sync." " Must be 44100 Hz.", sample_rate); } jack_set_process_callback(client, &process, NULL); jack_set_graph_order_callback(client, &graph, NULL); jack_set_error_function(&error); jack_set_info_function(&info); for (i = 0; i < NPORTS; i++) { port[i] = jack_port_register(client, port_name[i], JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0); } if (jack_activate(client)) { die("Could not activate %s JACK client.", config.jack_client_name); } else { debug(2, "JACK client %s activated sucessfully.", config.jack_client_name); } if (config.jack_autoconnect_pattern != NULL) { inform("config.jack_autoconnect_pattern is %s. If you see the program die after this," "you made a syntax error.", config.jack_autoconnect_pattern); // Sadly, this will throw a segfault if the user provides a syntactically incorrect regex. // I've reported it to the jack-devel mailing list, they're in a better place to fix it. const char **port_list = jack_get_ports(client, config.jack_autoconnect_pattern, JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput); if (port_list != NULL) { for (i = 0; i < NPORTS; i++) { char *full_port_name[NPORTS]; full_port_name[i] = malloc(sizeof(char) * jack_port_name_size()); sprintf(full_port_name[i], "%s:%s", config.jack_client_name, port_name[i]); if (port_list[i] != NULL) { int err; debug(2, "Connecting %s to %s.", full_port_name[i], port_list[i]); err = jack_connect(client, full_port_name[i], port_list[i]); switch (err) { case EEXIST: inform("The requested connection from %s to %s already exists.", full_port_name[i], port_list[i]); break; case 0: // success break; default: warn("JACK error no. %d occured while trying to connect %s to %s.", err, full_port_name[i], port_list[i]); break; } } else { inform("No matching port found in %s to connect %s to. You may not hear audio.", config.jack_autoconnect_pattern, full_port_name[i]); } free(full_port_name[i]); } while (port_list[i++] != NULL) { inform( "Additional matching port %s found. Check that the connections are what you intended."); } jack_free(port_list); } } pthread_mutex_unlock(&client_mutex); return 0; } void jack_deinit() { pthread_mutex_lock(&client_mutex); if (jack_deactivate(client)) warn("Error deactivating jack client"); if (jack_client_close(client)) warn("Error closing jack client"); pthread_mutex_unlock(&client_mutex); jack_ringbuffer_free(jackbuf); } void jack_start(__attribute__((unused)) int i_sample_rate, __attribute__((unused)) int i_sample_format) { // Nothing to do, JACK client has already been set up at jack_init(). // Also, we have no say over the sample rate or sample format of JACK, // We convert the 16bit samples to float, and die if the sample rate is != 44k1. // FIXME: later, resampling would be nice. Fold into soxr if possible. } void jack_flush() { debug(2, "Only the consumer can safely flush a lock-free ringbuffer. Asking the" " process callback to do it..."); flush_please = 1; } int jack_delay(long *the_delay) { // Semantics change: we now look at the last transfer into the lock-free // ringbuffer, not into the jack buffers directly (because locking those would // violate real-time constraints). On average, that should lead to just a // constant additional latency. // Without the mutex, we could get the time of what is the last transfer of data // to a jack buffer, but then a transfer could occur and we would get the buffer // occupancy after another transfer had occurred, so we could "lose" a full transfer // (e.g. 1024 frames @ 44,100 fps ~ 23.2 milliseconds) pthread_mutex_lock(&buffer_mutex); int64_t time_now = get_absolute_time_in_fp(); int64_t delta = time_now - time_of_latest_transfer; size_t audio_occupancy_now = jack_ringbuffer_read_space(jackbuf) / bytes_per_frame; debug(2, "audio_occupancy_now is %d.", audio_occupancy_now); pthread_mutex_unlock(&buffer_mutex); int64_t frames_processed_since_latest_latency_check = (delta * 44100) >> 32; // debug(1,"delta: %" PRId64 " frames.",frames_processed_since_latest_latency_check); // jack_latency is set by the graph() callback, it's the average of the maximum // latencies of all our output ports. Adjust this constant baseline delay according // to the buffer fill level: *the_delay = jack_latency + audio_occupancy_now - frames_processed_since_latest_latency_check; // debug(1,"reporting a delay of %d frames",*the_delay); return 0; } int play(void *buf, int samples) { // debug(1,"jack_play of %d samples.",samples); // copy the samples into the queue size_t bytes_to_transfer, bytes_transferred; bytes_to_transfer = samples * bytes_per_frame; // It's ok to lock here since we're not in the realtime callback: pthread_mutex_lock(&buffer_mutex); bytes_transferred = jack_ringbuffer_write(jackbuf, buf, bytes_to_transfer); time_of_latest_transfer = get_absolute_time_in_fp(); pthread_mutex_unlock(&buffer_mutex); if (bytes_transferred < bytes_to_transfer) { warn("JACK ringbuffer overrun. Only wrote %d of %d bytes.", bytes_transferred, bytes_to_transfer); } return 0; }