Reduced GStreamer H264 encoder latency

Changed x264enc properties to reduce latency

Author: alexey-kravtsov

README.md

@@ -62,6 +62,7 @@ Check out the **[contributing wiki](https://github.com/pion/webrtc/wiki/Contribu
 * [Lukas Herman](https://github.com/lherman-cs) - *C Data Channels example*
 * [EricSong](https://github.com/xsephiroth) - *Implement GstV4l2Alsa example*
 * [Tristan Matthews](https://github.com/tmatth)
+* [Alexey Kravtsov](https://github.com/alexey-kravtsov) - *GStreamer encoder tune*
 
 ### License
 MIT License - see [LICENSE](LICENSE) for full text

internal/gstreamer-src/gst.go

@@ -53,7 +53,7 @@ func CreatePipeline(codecName string, tracks []*webrtc.Track, pipelineSrc string
 		clockRate = videoClockRate
 
 	case webrtc.H264:
-		pipelineStr = pipelineSrc + " ! video/x-raw,format=I420 ! x264enc bframes=0 speed-preset=veryfast key-int-max=60 ! video/x-h264,stream-format=byte-stream ! " + pipelineStr
+		pipelineStr = pipelineSrc + " ! video/x-raw,format=I420 ! x264enc speed-preset=ultrafast tune=zerolatency key-int-max=20 ! video/x-h264,stream-format=byte-stream ! " + pipelineStr
 		clockRate = videoClockRate
 
 	case webrtc.Opus: