85 lines
3.6 KiB
C
85 lines
3.6 KiB
C
/*
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* dummy output driver. This file is part of Shairport.
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* Copyright (c) James Laird 2013
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* All rights reserved.
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*
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* Modifications for audio synchronisation
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* and related work, copyright (c) Mike Brady 2014 -- 2022
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "audio.h"
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#include "common.h"
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#include <inttypes.h> // for PRId64 and friends
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#include <stdio.h>
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#include <sys/time.h>
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#include <unistd.h>
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static int init(__attribute__((unused)) int argc, __attribute__((unused)) char **argv) { return 0; }
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static void deinit(void) {}
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static void start(int sample_rate, __attribute__((unused)) int sample_format) {
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debug(1, "dummy audio output started at %d frames per second.", sample_rate);
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}
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// clang-format off
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// Here is a brief explanation of the parameters:
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// sample_type is 'play_samples_are_untimed' or 'play_samples_are_timed' defined in audio.h.
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// 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.
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// timed samples come from the client.
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// timestamp is the RTP timestamp given to the first frame by the client
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// playtime is when the first frame should to be played. It is given in "local time".
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// 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)
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// clang-format on
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static int play(__attribute__((unused)) void *buf, __attribute__((unused)) int samples,
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int sample_type, uint32_t timestamp, uint64_t playtime) {
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// sample code using some of the extra information
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if (sample_type == play_samples_are_timed) {
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int64_t lead_time = playtime - get_absolute_time_in_ns();
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debug(2, "leadtime for frame %u is %" PRId64 " nanoseconds, i.e. %f seconds.", timestamp,
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lead_time, 0.000000001 * lead_time);
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}
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return 0;
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}
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static void stop(void) { debug(1, "dummy audio stopped\n"); }
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audio_output audio_dummy = {.name = "dummy",
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.help = NULL,
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.init = &init,
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.deinit = &deinit,
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.prepare = NULL,
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.start = &start,
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.stop = &stop,
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.is_running = NULL,
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.flush = NULL,
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.delay = NULL,
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.stats = NULL,
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.play = &play,
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.volume = NULL,
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.parameters = NULL,
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.mute = NULL};
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