From 9a4c230a563e1ad68d75114d0154821677c239d7 Mon Sep 17 00:00:00 2001
From: David Colburn <xero73@gmail.com>
Date: Thu, 3 Oct 2024 22:31:34 -0700
Subject: [PATCH] CBR for streams (#785)

---
 pkg/pipeline/builder/video.go | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/pkg/pipeline/builder/video.go b/pkg/pipeline/builder/video.go
index 7e00ccc6..4e6ada55 100644
--- a/pkg/pipeline/builder/video.go
+++ b/pkg/pipeline/builder/video.go
@@ -536,6 +536,7 @@ func (b *VideoBin) addEncoder() error {
 		if err != nil {
 			return errors.ErrGstPipelineError(err)
 		}
+
 		x264Enc.SetArg("speed-preset", "veryfast")
 		if b.conf.KeyFrameInterval != 0 {
 			keyframeInterval := uint(b.conf.KeyFrameInterval * float64(b.conf.Framerate))
@@ -543,12 +544,12 @@ func (b *VideoBin) addEncoder() error {
 				return errors.ErrGstPipelineError(err)
 			}
 		}
+
+		var options []string
 		bufCapacity := uint(2000) // 2s
 		if b.conf.GetSegmentConfig() != nil {
 			// avoid key frames other than at segments boundaries as splitmuxsink can become inconsistent otherwise
-			if err = x264Enc.SetProperty("option-string", "scenecut=0"); err != nil {
-				return errors.ErrGstPipelineError(err)
-			}
+			options = append(options, "scenecut=0")
 			bufCapacity = uint(time.Duration(b.conf.GetSegmentConfig().SegmentDuration) * (time.Second / time.Millisecond))
 		}
 		if bufCapacity > 10000 {
@@ -558,13 +559,21 @@ func (b *VideoBin) addEncoder() error {
 		if err = x264Enc.SetProperty("vbv-buf-capacity", bufCapacity); err != nil {
 			return errors.ErrGstPipelineError(err)
 		}
-		if b.conf.GetStreamConfig() != nil {
-			x264Enc.SetArg("pass", "cbr")
-		}
+
 		if err = x264Enc.SetProperty("bitrate", uint(b.conf.VideoBitrate)); err != nil {
 			return errors.ErrGstPipelineError(err)
 		}
 
+		if b.conf.GetStreamConfig() != nil {
+			options = append(options, "nal-hrd=cbr")
+		}
+		if len(options) > 0 {
+			optionString := strings.Join(options, ":")
+			if err = x264Enc.SetProperty("option-string", optionString); err != nil {
+				return errors.ErrGstPipelineError(err)
+			}
+		}
+
 		caps, err := gst.NewElement("capsfilter")
 		if err != nil {
 			return errors.ErrGstPipelineError(err)