mac-avcapture: Default to unbuffered video capture

By default, video plays back based upon the timestamp for each frame,
and buffers the frames as needed to ensure that they play back at the
expected timing.

However, this can add some minor additional delay to the video, and may
not be ideal for certain devices such as webcams and generally any
device that has minimal latency.  However, because those are the only
type of devices that typically have drivers, there's no real need to
have it on by default.

This adds an option to use buffering, and leaves it off by default.

Closes pull request #384

(message added by jim)

plugins/mac-avcapture/av-capture.m

@@ -243,6 +243,18 @@ static inline bool update_frame(struct av_capture *capture,
 }
 @end
 
+static void av_capture_enable_buffering(struct av_capture *capture,
+		bool enabled)
+{
+	obs_source_t *source = capture->source;
+	uint32_t flags = obs_source_get_flags(source);
+	if (enabled)
+		flags &= ~OBS_SOURCE_FLAG_UNBUFFERED;
+	else
+		flags |= OBS_SOURCE_FLAG_UNBUFFERED;
+	obs_source_set_flags(source, flags);
+}
+
 static const char *av_capture_getname(void)
 {
 	return TEXT_AVCAPTURE;
@@ -569,6 +581,9 @@ static void *av_capture_create(obs_data_t *settings, obs_source_t *source)
 		capture = NULL;
 	}
 
+	av_capture_enable_buffering(capture,
+			obs_data_get_bool(settings, "buffering"));
+
 	return capture;
 }
 
@@ -805,6 +820,9 @@ static obs_properties_t *av_capture_properties(void *unused)
 	obs_property_set_modified_callback(preset_list,
 			properties_preset_changed);
 
+	obs_properties_add_bool(props, "buffering",
+			obs_module_text("Buffering"));
+
 	return props;
 }
 
@@ -847,6 +865,9 @@ static void av_capture_update(void *data, obs_data_t *settings)
 
 	capture->session.sessionPreset = preset;
 	AVLOG(LOG_INFO, "Selected preset %s", preset.UTF8String);
+
+	av_capture_enable_buffering(capture,
+			obs_data_get_bool(settings, "buffering"));
 }
 
 struct obs_source_info av_capture_info = {

plugins/mac-avcapture/data/locale/en-US.ini

@@ -2,3 +2,4 @@ AVCapture="Video Capture Device"
 Device="Device"
 UsePreset="Use Preset"
 Preset="Preset"
+Buffering="Use Buffering"