obs-filters: Add async delay filter

Adds a filter for delaying asynchronous video/audio data, for example
from webcams, video devices, or media playback sources.  Mainly intended
to allow users to sync up their webcams to other devices.

plugins/CMakeLists.txt

@@ -22,5 +22,6 @@ add_subdirectory(obs-x264)
 add_subdirectory(obs-libfdk)
 add_subdirectory(obs-ffmpeg)
 add_subdirectory(obs-outputs)
+add_subdirectory(obs-filters)
 add_subdirectory(rtmp-services)
 add_subdirectory(text-freetype2)

plugins/obs-filters/CMakeLists.txt

@@ -0,0 +1,12 @@
+project(obs-filters)
+
+set(obs-filters_SOURCES
+	obs-filters.c
+	async-delay-filter.c)
+
+add_library(obs-filters MODULE
+	${obs-filters_SOURCES})
+target_link_libraries(obs-filters
+	libobs)
+
+install_obs_plugin_with_data(obs-filters data)

plugins/obs-filters/async-delay-filter.c

@@ -0,0 +1,243 @@
+#include <obs-module.h>
+#include <util/circlebuf.h>
+
+#ifndef SEC_TO_NSEC
+#define SEC_TO_NSEC 1000000000ULL
+#endif
+
+#ifndef MSEC_TO_NSEC
+#define MSEC_TO_NSEC 1000000ULL
+#endif
+
+#define SETTING_DELAY_MS               "delay_ms"
+
+#define TEXT_DELAY_MS                  obs_module_text("DelayMs")
+
+struct async_delay_data {
+	obs_source_t                   *context;
+
+	/* contains struct obs_source_frame* */
+	struct circlebuf               video_frames;
+
+	/* stores the audio data */
+	struct circlebuf               audio_frames;
+	struct obs_audio_data          audio_output;
+
+	uint64_t                       last_video_ts;
+	uint64_t                       last_audio_ts;
+	uint64_t                       interval;
+	uint64_t                       samplerate;
+	bool                           video_delay_reached;
+	bool                           audio_delay_reached;
+	bool                           reset_video;
+	bool                           reset_audio;
+};
+
+static const char *async_delay_filter_name(void)
+{
+	return obs_module_text("AsyncDelayFilter");
+}
+
+static void free_video_data(struct async_delay_data *filter,
+		obs_source_t *parent)
+{
+	while (filter->video_frames.size) {
+		struct obs_source_frame *frame;
+
+		circlebuf_pop_front(&filter->video_frames, &frame,
+				sizeof(struct obs_source_frame*));
+		obs_source_release_frame(parent, frame);
+	}
+}
+
+static inline void free_audio_packet(struct obs_audio_data *audio)
+{
+	for (size_t i = 0; i < MAX_AV_PLANES; i++)
+		bfree(audio->data[i]);
+	memset(audio, 0, sizeof(*audio));
+}
+
+static void free_audio_data(struct async_delay_data *filter)
+{
+	while (filter->audio_frames.size) {
+		struct obs_audio_data audio;
+
+		circlebuf_pop_front(&filter->audio_frames, &audio,
+				sizeof(struct obs_audio_data));
+		free_audio_packet(&audio);
+	}
+}
+
+static void async_delay_filter_update(void *data, obs_data_t *settings)
+{
+	struct async_delay_data *filter = data;
+	uint64_t new_interval = (uint64_t)obs_data_get_int(settings,
+			SETTING_DELAY_MS) * MSEC_TO_NSEC;
+
+	if (new_interval < filter->interval)
+		free_video_data(filter, obs_filter_get_parent(filter->context));
+
+	filter->reset_audio = true;
+	filter->reset_video = true;
+	filter->interval = new_interval;
+	filter->video_delay_reached = false;
+	filter->audio_delay_reached = false;
+}
+
+static void *async_delay_filter_create(obs_data_t *settings,
+		obs_source_t *context)
+{
+	struct async_delay_data *filter = bzalloc(sizeof(*filter));
+	struct obs_audio_info oai;
+
+	filter->context = context;
+	async_delay_filter_update(filter, settings);
+
+	obs_get_audio_info(&oai);
+	filter->samplerate = oai.samples_per_sec;
+
+	return filter;
+}
+
+static void async_delay_filter_destroy(void *data)
+{
+	struct async_delay_data *filter = data;
+
+	free_audio_packet(&filter->audio_output);
+	circlebuf_free(&filter->video_frames);
+	circlebuf_free(&filter->audio_frames);
+	bfree(data);
+}
+
+static obs_properties_t *async_delay_filter_properties(void *data)
+{
+	obs_properties_t *props = obs_properties_create();
+
+	obs_properties_add_int(props, SETTING_DELAY_MS, TEXT_DELAY_MS,
+			0, 6000, 1);
+
+	UNUSED_PARAMETER(data);
+	return props;
+}
+
+static void async_delay_filter_remove(void *data, obs_source_t *parent)
+{
+	struct async_delay_data *filter = data;
+
+	free_video_data(filter, parent);
+	free_audio_data(filter);
+}
+
+/* due to the fact that we need timing information to be consistent in order to
+ * measure the current interval of data, if there is an unexpected hiccup or
+ * jump with the timestamps, reset the cached delay data and start again to
+ * ensure that the timing is consistent */
+static inline bool is_timestamp_jump(uint64_t ts, uint64_t prev_ts)
+{
+	return ts < prev_ts || (ts - prev_ts) > SEC_TO_NSEC;
+}
+
+static struct obs_source_frame *async_delay_filter_video(void *data,
+		struct obs_source_frame *frame)
+{
+	struct async_delay_data *filter = data;
+	obs_source_t *parent = obs_filter_get_parent(filter->context);
+	struct obs_source_frame *output;
+	uint64_t cur_interval;
+
+	if (filter->reset_video ||
+	    is_timestamp_jump(frame->timestamp, filter->last_video_ts)) {
+		free_video_data(filter, parent);
+		filter->video_delay_reached = false;
+		filter->reset_video = false;
+	}
+
+	filter->last_video_ts = frame->timestamp;
+
+	circlebuf_push_back(&filter->video_frames, &frame,
+			sizeof(struct obs_source_frame*));
+	circlebuf_peek_front(&filter->video_frames, &output,
+			sizeof(struct obs_source_frame*));
+
+	cur_interval = frame->timestamp - output->timestamp;
+	if (!filter->video_delay_reached && cur_interval < filter->interval)
+		return NULL;
+
+	circlebuf_pop_front(&filter->video_frames, NULL,
+			sizeof(struct obs_source_frame*));
+
+	if (!filter->video_delay_reached)
+		filter->video_delay_reached = true;
+
+	return output;
+}
+
+/* NOTE: Delaying audio shouldn't be necessary because the audio subsystem will
+ * automatically sync audio to video frames */
+
+/* #define DELAY_AUDIO */
+
+#ifdef DELAY_AUDIO
+static struct obs_audio_data *async_delay_filter_audio(void *data,
+		struct obs_audio_data *audio)
+{
+	struct async_delay_data *filter = data;
+	struct obs_audio_data cached = *audio;
+	uint64_t cur_interval;
+	uint64_t duration;
+	uint64_t end_ts;
+
+	if (filter->reset_audio ||
+	    is_timestamp_jump(audio->timestamp, filter->last_audio_ts)) {
+		free_audio_data(filter);
+		filter->audio_delay_reached = false;
+		filter->reset_audio = false;
+	}
+
+	filter->last_audio_ts = audio->timestamp;
+
+	duration = (uint64_t)audio->frames * SEC_TO_NSEC / filter->samplerate;
+	end_ts = audio->timestamp + duration;
+
+	for (size_t i = 0; i < MAX_AV_PLANES; i++) {
+		if (!audio->data[i])
+			break;
+
+		cached.data[i] = bmemdup(audio->data[i],
+				audio->frames * sizeof(float));
+	}
+
+	free_audio_packet(&filter->audio_output);
+
+	circlebuf_push_back(&filter->audio_frames, &cached, sizeof(cached));
+	circlebuf_peek_front(&filter->audio_frames, &cached, sizeof(cached));
+
+	cur_interval = end_ts - cached.timestamp;
+	if (!filter->audio_delay_reached && cur_interval < filter->interval)
+		return NULL;
+
+	circlebuf_pop_front(&filter->audio_frames, NULL, sizeof(cached));
+	memcpy(&filter->audio_output, &cached, sizeof(cached));
+
+	if (!filter->audio_delay_reached)
+		filter->audio_delay_reached = true;
+
+	return &filter->audio_output;
+}
+#endif
+
+struct obs_source_info async_delay_filter = {
+	.id                            = "async_delay_filter",
+	.type                          = OBS_SOURCE_TYPE_FILTER,
+	.output_flags                  = OBS_SOURCE_VIDEO | OBS_SOURCE_ASYNC,
+	.get_name                      = async_delay_filter_name,
+	.create                        = async_delay_filter_create,
+	.destroy                       = async_delay_filter_destroy,
+	.update                        = async_delay_filter_update,
+	.get_properties                = async_delay_filter_properties,
+	.filter_video                  = async_delay_filter_video,
+#ifdef DELAY_AUDIO
+	.filter_audio                  = async_delay_filter_audio,
+#endif
+	.filter_remove                 = async_delay_filter_remove
+};

plugins/obs-filters/data/locale/en-US.ini

@@ -0,0 +1,2 @@
+AsyncDelayFilter="Video Delay (Async)"
+DelayMs="Delay (milliseconds)"

plugins/obs-filters/obs-filters.c

@@ -0,0 +1,13 @@
+#include <obs-module.h>
+
+OBS_DECLARE_MODULE()
+
+OBS_MODULE_USE_DEFAULT_LOCALE("obs-filters", "en-US")
+
+extern struct obs_source_info async_delay_filter;
+
+bool obs_module_load(void)
+{
+	obs_register_source(&async_delay_filter);
+	return true;
+}