Fixed broken VP9-SVC demo (fixes #3169)

Author: lminiero

conf/janus.plugin.videoroom.jcfg.sample

@@ -88,7 +88,7 @@ room-5678: {
 	description = "VP9-SVC Demo Room"
 	secret = "adminpwd"
 	publishers = 6
-	bitrate = 512000
+	bitrate = 0		# No limit, to give room for all layers
 	fir_freq = 10
 	videocodec = "vp9"
 	video_svc = true

html/vp9svctest.html

@@ -61,13 +61,11 @@ <h3>Demo details</h3>
 						you have a single stream with multiple layers, which makes it more efficient,
 						especially because it consumes much less bandwidth.</p>
 						<p>Notice that this only works if the publishers joining the room will use a recent
-						Chrome version that has been started either with the following flag:</p>
-						<p><div class="alert alert-info"><code>--force-fieldtrials=WebRTC-SupportVP9SVC/EnabledByFlag_2SL3TL/</code></div></p>
-						<p>to configure VP9 SVC to only use two spatial layers, or:</p>
-						<p><div class="alert alert-info"><code>--force-fieldtrials=WebRTC-SupportVP9SVC/EnabledByFlag_3SL3TL/</code></div></p>
-						<p>to test three spatial layers instead.
-						If you join with a Chrome that doesn't have one of those options set, or with
-						another browser, you'll be able to select a layer, but all request to set
+						browser that supports the <code>scalabilityMode</code> property in <code>sendEncodings</code>,
+						e.g., recent Chrome versions (please refer to the
+						<a target="_blank" href="https://www.w3.org/TR/webrtc-svc/">SVC Extension for WebRTC</a>
+						documentation for more details). If you join with a browser that doesn't support
+						those properties, or with you'll be able to select a layer, but all request to set
 						a custom layer on your video will fail, meaning you'll act as a plain VP9 client.
 						If you ask for a layer from a publisher that doesn't support VP9 SVC either,
 						then your request will be ignored as well.</p>

html/vp9svctest.js

@@ -434,7 +434,9 @@ function publishOwnFeed(useAudio) {
 	let tracks = [];
 	if(useAudio)
 		tracks.push({ type: 'audio', capture: true, recv: false });
-	tracks.push({ type: 'video', capture: true, recv: false, simulcast: false});
+	// For video, we add the 'svc' property to set the related scalabilityMode:
+	// since we'll force VP9, this will enable SVC mode in the VP9 encoder
+	tracks.push({ type: 'video', capture: true, recv: false, svc: 'S3T3' });
 	//~ tracks.push({ type: 'data' });
 
 	sfutest.createOffer(

src/plugins/janus_videoroom.c

@@ -3138,6 +3138,8 @@ static void janus_videoroom_create_dummy_publisher(janus_videoroom *room, GHashT
 			ps->h264_profile = g_strdup(room->h264_profile);
 		else if(ps->vcodec == JANUS_VIDEOCODEC_VP9 && ps->vp9_profile == NULL && room->vp9_profile != NULL)
 			ps->vp9_profile = g_strdup(room->vp9_profile);
+		if(ps->vcodec == JANUS_VIDEOCODEC_VP9 && room->do_svc)
+			ps->svc = TRUE;	/* FIXME */
 		ps->min_delay = -1;
 		ps->max_delay = -1;
 		g_atomic_int_set(&ps->destroyed, 0);
@@ -12162,6 +12164,8 @@ static void *janus_videoroom_handler(void *data) {
 									janus_mutex_unlock(&ps->rid_mutex);
 								}
 							}
+							if(ps->vcodec == JANUS_VIDEOCODEC_VP9 && videoroom->do_svc)
+								ps->svc = TRUE;	/* FIXME */
 							mdir = (ps->vcodec != JANUS_VIDEOCODEC_NONE ? JANUS_SDP_RECVONLY : JANUS_SDP_INACTIVE);
 						} else if(m->type == JANUS_SDP_APPLICATION) {
 							mdir = JANUS_SDP_RECVONLY;