Merge pull request #3 from MB-Finski/patch-1

Add support for NVIDIA GPU accelerated transcoding

stream.go

@@ -357,12 +357,16 @@ func (s *Stream) transcodeArgs(startAt float64) []string {
 	// encoder selection
 	CV := "libx264"
 
-	// no need to transcode h264 streams for max quality
+	// Check whether hwaccel should be used
 	if os.Getenv("VAAPI") == "1" {
 		CV = "h264_vaapi"
 		extra := "-hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi"
 		args = append(args, strings.Split(extra, " ")...)
-	}
+	} else if os.Getenv("NVENC") == "1" {
+                CV = "h264_nvenc"
+                extra := "-hwaccel cuda -hwaccel_output_format cuda"
+                args = append(args, strings.Split(extra, " ")...)
+        } 
 
 	// Input specs
 	args = append(args, []string{
@@ -378,7 +382,11 @@ func (s *Stream) transcodeArgs(startAt float64) []string {
 		// VAAPI
 		format = "format=nv12|vaapi,hwupload"
 		scale = fmt.Sprintf("scale_vaapi=w=%d:h=%d:force_original_aspect_ratio=decrease", s.width, s.height)
-	} else {
+	} else if CV == "h264_nvenc" {
+                // NVENC
+		format = "format=nv12|cuda,hwupload"
+		scale = fmt.Sprintf("scale_cuda=w=%d:h=%d:force_original_aspect_ratio=decrease:passthrough=0", s.width, s.height)
+        } else {
 		// x264
 		format = "format=nv12"
 		if s.width >= s.height {
@@ -390,15 +398,22 @@ func (s *Stream) transcodeArgs(startAt float64) []string {
 
 	// do not scale or set bitrate for full quality
 	if s.quality == "max" {
-		args = append(args, []string{
-			"-vf", format,
-		}...)
+		if CV == "h264_nvenc" {
+			// Due to a bug(?) in NVENC, passthrough=0 must be set
+			args = append(args, []string{
+                                "-vf", fmt.Sprintf("%s,%s", format, "scale_cuda=passthrough=0"),
+                        }...)
+                } else {
+                        args = append(args, []string{
+                                "-vf", format,
+                        }...)
+                }
 	} else {
 		args = append(args, []string{
 			"-vf", fmt.Sprintf("%s,%s", format, scale),
-			"-maxrate", fmt.Sprintf("%d", s.bitrate),
-			"-bufsize", fmt.Sprintf("%d", s.bitrate*2),
-		}...)
+                        "-maxrate", fmt.Sprintf("%d", s.bitrate),
+                        "-bufsize", fmt.Sprintf("%d", s.bitrate*2),
+                }...)
 	}
 
 	// Output specs
@@ -413,6 +428,15 @@ func (s *Stream) transcodeArgs(startAt float64) []string {
 			"-low_power", "1",
 			"-global_quality", "25",
 		}...)
+	} else if CV == "h264_nvenc" {
+                args = append(args, []string{
+                        "-preset", "p6",
+                        "-tune", "ll",
+                        "-temporal-aq", "1",
+                        "-rc", "vbr",
+                        "-rc-lookahead","30",
+                        "-cq", "24",
+                }...)
 	} else if CV == "libx264" {
 		args = append(args, []string{
 			"-preset", "faster",