libobs: Add surround sound audio support

(This commit also modifies the following modules: UI,
deps/media-playback, coreaudio-encoder, decklink, linux-alsa,
linux-pulseaudio, mac-capture, obs-ffmpeg, obs-filters, obs-libfdk,
obs-outputs, win-dshow, and win-wasapi)

Adds surround sound audio support to the core, core plugins, and user
interface.

Compatible streaming services: Twitch, FB 360 live
Compatible protocols: rtmp / mpeg-ts tcp udp
Compatible file formats: mkv mp4 ts  (others untested)
Compatible codecs: ffmpeg aac, fdk_aac, CoreAudio aac,
		   opus, vorbis, pcm (others untested).
Tested streaming servers: wowza, nginx
	 HLS, mpeg-dash : surround passthrough
Html5 players tested with live surround:
	 videojs, mediaelement, viblast (hls+dash), hls.js
Decklink: on win32, swap channels order for 5.1 7.1
         (due to different channel mapping on wav, mpeg, ffmpeg)
Audio filters: surround working.
Monitoring: surround working (win macOs linux (pulse-audio)).
VST:	 stereo plugins keep in general only the first two channels.
	 surround plugins should work (e.g. mcfx does).
OS: win, macOs, linux (alsa, pulse-audio).
Misc: larger audio bitrates unlocked to accommodate more channels
NB: mf-aac only supports mono and stereo + 5.1 on win 10
         (not implemented due to lack of usefulness)

Closes jp9000/obs-studio#968

plugins/obs-filters/gain-filter.c

@@ -16,6 +16,7 @@
 
 struct gain_data {
 	obs_source_t *context;
+	size_t channels;
 	float multiple;
 };
 
@@ -35,7 +36,7 @@ static void gain_update(void *data, obs_data_t *s)
 {
 	struct gain_data *gf = data;
 	double val = obs_data_get_double(s, S_GAIN_DB);
-
+	gf->channels = audio_output_get_channels(obs_get_audio());
 	gf->multiple = db_to_mul((float)val);
 }
 
@@ -51,11 +52,11 @@ static struct obs_audio_data *gain_filter_audio(void *data,
 		struct obs_audio_data *audio)
 {
 	struct gain_data *gf = data;
-
-	float *adata[2] = {(float*)audio->data[0], (float*)audio->data[1]};
+	const size_t channels = gf->channels;
+	float **adata = (float**)audio->data;
 	const float multiple = gf->multiple;
 
-	for (size_t c = 0; c < 2; c++) {
+	for (size_t c = 0; c < channels; c++) {
 		if (audio->data[c]) {
 			for (size_t i = 0; i < audio->frames; i++) {
 				adata[c][i] *= multiple;

plugins/obs-filters/noise-gate-filter.c

@@ -109,7 +109,7 @@ static struct obs_audio_data *noise_gate_filter_audio(void *data,
 {
 	struct noise_gate_data *ng = data;
 
-	float *adata[2] = {(float*)audio->data[0], (float*)audio->data[1]};
+	float **adata = (float**)audio->data;
 	const float close_threshold = ng->close_threshold;
 	const float open_threshold = ng->open_threshold;
 	const float sample_rate_i = ng->sample_rate_i;
@@ -120,9 +120,10 @@ static struct obs_audio_data *noise_gate_filter_audio(void *data,
 	const size_t channels = ng->channels;
 
 	for (size_t i = 0; i < audio->frames; i++) {
-		float cur_level = (channels == 2)
-			? fmaxf(fabsf(adata[0][i]), fabsf(adata[1][i]))
-			: fabsf(adata[0][i]);
+		float cur_level = fabsf(adata[0][i]);
+		for (size_t j = 0; j < channels; j++) {
+			cur_level = fmaxf(cur_level, fabsf(adata[j][i]));
+		}
 
 		if (cur_level > open_threshold && !ng->is_open) {
 			ng->is_open = true;

plugins/obs-filters/noise-suppress-filter.c

@@ -27,7 +27,7 @@
 #define MT_ obs_module_text
 #define TEXT_SUPPRESS_LEVEL             MT_("NoiseSuppress.SuppressLevel")
 
-#define MAX_PREPROC_CHANNELS            2
+#define MAX_PREPROC_CHANNELS            8
 
 /* -------------------------------------------------------- */
 
@@ -120,12 +120,12 @@ static void noise_suppress_update(void *data, obs_data_t *s)
 	/* One speex state for each channel (limit 2) */
 	ng->copy_buffers[0] = bmalloc(frames * channels * sizeof(float));
 	ng->segment_buffers[0] = bmalloc(frames * channels * sizeof(spx_int16_t));
-
-	if (channels == 2) {
-		ng->copy_buffers[1] = ng->copy_buffers[0] + frames;
-		ng->segment_buffers[1] = ng->segment_buffers[0] + frames;
+	for (size_t c = 1; c < channels; ++c) {
+		ng->copy_buffers[c] = ng->copy_buffers[c-1] + frames;
+		ng->segment_buffers[c] = ng->segment_buffers[c-1] + frames;
 	}
 
+
 	for (size_t i = 0; i < channels; i++)
 		alloc_channel(ng, sample_rate, i, frames);
 }