/* * dummy output driver. This file is part of Shairport. * Copyright (c) James Laird 2013 * All rights reserved. * * Modifications for audio synchronisation * and related work, copyright (c) Mike Brady 2014--2025 * All rights reserved. * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, * copy, modify, merge, publish, distribute, sublicense, and/or * sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. */ #include "audio.h" #include "common.h" #include // for PRId64 and friends #include #include #include static int init(__attribute__((unused)) int argc, __attribute__((unused)) char **argv) { return 0; } static void deinit(void) {} static void start(int sample_rate, __attribute__((unused)) int sample_format) { debug(1, "dummy audio output started at %d frames per second.", sample_rate); } // clang-format off // Here is a brief explanation of the parameters: // sample_type is 'play_samples_are_untimed' or 'play_samples_are_timed' defined in audio.h. // untimed samples are typically silence used by Shairport Sync itself to set up synchronisation or to fill for missing packets of audio -- the timestamp and playtime are zero. // timed samples come from the client. // timestamp is the RTP timestamp given to the first frame by the client // playtime is when the first frame should to be played. It is given in "local time". // local time is CLOCK_MONOTONIC_RAW if available, or CLOCK_MONOTONIC otherwise, expressed in nanoseconds as an unsigned 64-bit integer (See get_absolute_time_in_ns() in common.c) // clang-format on static int play(__attribute__((unused)) void *buf, __attribute__((unused)) int samples, int sample_type, uint32_t timestamp, uint64_t playtime) { // sample code using some of the extra information if (sample_type == play_samples_are_timed) { int64_t lead_time = playtime - get_absolute_time_in_ns(); debug(2, "leadtime for frame %u is %" PRId64 " nanoseconds, i.e. %f seconds.", timestamp, lead_time, 0.000000001 * lead_time); } return 0; } static void stop(void) { debug(1, "dummy audio stopped\n"); } audio_output audio_dummy = {.name = "dummy", .help = NULL, .init = &init, .deinit = &deinit, .configure = NULL, .start = &start, .stop = &stop, .is_running = NULL, .flush = NULL, .delay = NULL, .stats = NULL, .play = &play, .volume = NULL, .parameters = NULL, .mute = NULL};