1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>
4
5 This software is provided 'as-is', without any express or implied
6 warranty. In no event will the authors be held liable for any damages
7 arising from the use of this software.
8
9 Permission is granted to anyone to use this software for any purpose,
10 including commercial applications, and to alter it and redistribute it
11 freely, subject to the following restrictions:
12
13 1. The origin of this software must not be misrepresented; you must not
14 claim that you wrote the original software. If you use this software
15 in a product, an acknowledgment in the product documentation would be
16 appreciated but is not required.
17 2. Altered source versions must be plainly marked as such, and must not be
18 misrepresented as being the original software.
19 3. This notice may not be removed or altered from any source distribution.
20*/
21#include "SDL_internal.h"
22
23// Output audio to nowhere...
24
25#include "../SDL_sysaudio.h"
26#include "SDL_dummyaudio.h"
27
28#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
29#include <emscripten/emscripten.h>
30#endif
31
32static bool DUMMYAUDIO_WaitDevice(SDL_AudioDevice *device)
33{
34 SDL_Delay(device->hidden->io_delay);
35 return true;
36}
37
38static bool DUMMYAUDIO_OpenDevice(SDL_AudioDevice *device)
39{
40 device->hidden = (struct SDL_PrivateAudioData *) SDL_calloc(1, sizeof(*device->hidden));
41 if (!device->hidden) {
42 return false;
43 }
44
45 if (!device->recording) {
46 device->hidden->mixbuf = (Uint8 *) SDL_malloc(device->buffer_size);
47 if (!device->hidden->mixbuf) {
48 return false;
49 }
50 }
51
52 device->hidden->io_delay = ((device->sample_frames * 1000) / device->spec.freq);
53
54 const char *hint = SDL_GetHint(SDL_HINT_AUDIO_DUMMY_TIMESCALE);
55 if (hint) {
56 double scale = SDL_atof(hint);
57 if (scale >= 0.0) {
58 device->hidden->io_delay = (Uint32)SDL_round(device->hidden->io_delay * scale);
59 }
60 }
61
62 // on Emscripten without threads, we just fire a repeating timer to consume audio.
63 #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
64 MAIN_THREAD_EM_ASM({
65 var a = Module['SDL3'].dummy_audio;
66 if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
67 a.timers[$0] = setInterval(function() { dynCall('vi', $3, [$4]); }, ($1 / $2) * 1000);
68 }, device->recording ? 1 : 0, device->sample_frames, device->spec.freq, device->recording ? SDL_RecordingAudioThreadIterate : SDL_PlaybackAudioThreadIterate, device);
69 #endif
70
71 return true; // we're good; don't change reported device format.
72}
73
74static void DUMMYAUDIO_CloseDevice(SDL_AudioDevice *device)
75{
76 if (device->hidden) {
77 // on Emscripten without threads, we just fire a repeating timer to consume audio.
78 #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
79 MAIN_THREAD_EM_ASM({
80 var a = Module['SDL3'].dummy_audio;
81 if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
82 a.timers[$0] = undefined;
83 }, device->recording ? 1 : 0);
84 #endif
85 SDL_free(device->hidden->mixbuf);
86 SDL_free(device->hidden);
87 device->hidden = NULL;
88 }
89}
90
91static Uint8 *DUMMYAUDIO_GetDeviceBuf(SDL_AudioDevice *device, int *buffer_size)
92{
93 return device->hidden->mixbuf;
94}
95
96static int DUMMYAUDIO_RecordDevice(SDL_AudioDevice *device, void *buffer, int buflen)
97{
98 // always return a full buffer of silence.
99 SDL_memset(buffer, device->silence_value, buflen);
100 return buflen;
101}
102
103static bool DUMMYAUDIO_Init(SDL_AudioDriverImpl *impl)
104{
105 impl->OpenDevice = DUMMYAUDIO_OpenDevice;
106 impl->CloseDevice = DUMMYAUDIO_CloseDevice;
107 impl->WaitDevice = DUMMYAUDIO_WaitDevice;
108 impl->GetDeviceBuf = DUMMYAUDIO_GetDeviceBuf;
109 impl->WaitRecordingDevice = DUMMYAUDIO_WaitDevice;
110 impl->RecordDevice = DUMMYAUDIO_RecordDevice;
111
112 impl->OnlyHasDefaultPlaybackDevice = true;
113 impl->OnlyHasDefaultRecordingDevice = true;
114 impl->HasRecordingSupport = true;
115
116 // on Emscripten without threads, we just fire a repeating timer to consume audio.
117 #if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
118 MAIN_THREAD_EM_ASM({
119 if (typeof(Module['SDL3']) === 'undefined') {
120 Module['SDL3'] = {};
121 }
122 Module['SDL3'].dummy_audio = {};
123 Module['SDL3'].dummy_audio.timers = [];
124 Module['SDL3'].dummy_audio.timers[0] = undefined;
125 Module['SDL3'].dummy_audio.timers[1] = undefined;
126 });
127 impl->ProvidesOwnCallbackThread = true;
128 #endif
129
130 return true;
131}
132
133AudioBootStrap DUMMYAUDIO_bootstrap = {
134 "dummy", "SDL dummy audio driver", DUMMYAUDIO_Init, true, false
135};
136