Transcoder updates for bitrate validator warnings (#106)

* Transcoder updates for validator warnings (gop, max-bitrates) for #50

* Make the variant settings easier to set/read in code

* Update test to reflect update to transcoder

* Reduce the buffer to give it a little more room to improve the quality. It feels a bit crunched right now.

* Fix test due to changed bitrate buffer ratios

* Tweak buffer size one more time to get errors in the validator to zero

* Saw errors w/ different bitrates, so tweaking it again

config/config.go

@@ -197,6 +197,15 @@ func (c *config) GetVideoStreamQualities() []StreamQuality {
 	return _default.VideoSettings.StreamQualities
 }
 
+// GetFramerate returns the framerate or default
+func (q *StreamQuality) GetFramerate() int {
+	if q.Framerate > 0 {
+		return q.Framerate
+	}
+
+	return _default.VideoSettings.StreamQualities[0].Framerate
+}
+
 //Load tries to load the configuration file
 func Load(filePath string, versionInfo string) error {
 	Config = new(config)

config/defaults.go

@@ -21,6 +21,7 @@ func getDefaults() config {
 		IsAudioPassthrough: true,
 		VideoBitrate:       1200,
 		EncoderPreset:      "veryfast",
+		Framerate:          24,
 	}
 	defaults.VideoSettings.StreamQualities = []StreamQuality{defaultQuality}
 

core/ffmpeg/transcoder.go

@@ -33,7 +33,7 @@ type HLSVariant struct {
 
 	videoSize          VideoSize // Resizes the video via scaling
 	framerate          int       // The output framerate
-	videoBitrate       string    // The output bitrate
+	videoBitrate       int       // The output bitrate
 	isVideoPassthrough bool      // Override all settings and just copy the video stream
 
 	audioBitrate       string // The audio bitrate
@@ -164,11 +164,11 @@ func getVariantFromConfigQuality(quality config.StreamQuality, index int) HLSVar
 		variant.encoderPreset = "veryfast"
 	}
 
-	variant.SetVideoBitrate(strconv.Itoa(quality.VideoBitrate) + "k")
+	variant.SetVideoBitrate(quality.VideoBitrate)
 	variant.SetAudioBitrate(strconv.Itoa(quality.AudioBitrate) + "k")
 	variant.SetVideoScalingWidth(quality.ScaledWidth)
 	variant.SetVideoScalingHeight(quality.ScaledHeight)
-	variant.SetVideoFramerate(quality.Framerate)
+	variant.SetVideoFramerate(quality.GetFramerate())
 
 	return variant
 }
@@ -196,13 +196,6 @@ func NewTranscoder() Transcoder {
 	transcoder.segmentLengthSeconds = config.Config.GetVideoSegmentSecondsLength()
 
 	qualities := config.Config.VideoSettings.StreamQualities
-	if len(qualities) == 0 {
-		defaultQuality := config.StreamQuality{}
-		defaultQuality.VideoBitrate = 1000
-		defaultQuality.EncoderPreset = "superfast"
-		qualities = append(qualities, defaultQuality)
-	}
-
 	for index, quality := range qualities {
 		variant := getVariantFromConfigQuality(quality, index)
 		transcoder.AddVariant(variant)
@@ -212,9 +205,9 @@ func NewTranscoder() Transcoder {
 }
 
 // Uses `map` https://www.ffmpeg.org/ffmpeg-all.html#Stream-specifiers-1 https://www.ffmpeg.org/ffmpeg-all.html#Advanced-options
-func (v *HLSVariant) getVariantString() string {
+func (v *HLSVariant) getVariantString(t *Transcoder) string {
 	variantEncoderCommands := []string{
-		v.getVideoQualityString(),
+		v.getVideoQualityString(t),
 		v.getAudioQualityString(),
 	}
 
@@ -222,17 +215,7 @@ func (v *HLSVariant) getVariantString() string {
 		variantEncoderCommands = append(variantEncoderCommands, v.getScalingString())
 	}
 
-	if v.framerate == 0 {
-		v.framerate = 30
-	}
-
-	if v.framerate != 0 {
-		variantEncoderCommands = append(variantEncoderCommands, fmt.Sprintf("-r %d", v.framerate))
-		// Insert a keyframe every 2 seconds.
-		// Multiply your output frame rate * 2. For example, if your input is -framerate 30, then use -g 60
-		variantEncoderCommands = append(variantEncoderCommands, "-g "+strconv.Itoa(v.framerate*2))
-		variantEncoderCommands = append(variantEncoderCommands, "-keyint_min "+strconv.Itoa(v.framerate*2))
-	}
+	variantEncoderCommands = append(variantEncoderCommands, fmt.Sprintf("-r %d", v.framerate))
 
 	if v.encoderPreset != "" {
 		variantEncoderCommands = append(variantEncoderCommands, fmt.Sprintf("-preset %s", v.encoderPreset))
@@ -247,7 +230,7 @@ func (t *Transcoder) getVariantsString() string {
 	var variantsStreamMaps = " -var_stream_map \""
 
 	for _, variant := range t.variants {
-		variantsCommandFlags = variantsCommandFlags + " " + variant.getVariantString()
+		variantsCommandFlags = variantsCommandFlags + " " + variant.getVariantString(t)
 		variantsStreamMaps = variantsStreamMaps + fmt.Sprintf("v:%d,a:%d ", variant.index, variant.index)
 	}
 	variantsCommandFlags = variantsCommandFlags + " " + variantsStreamMaps + "\""
@@ -278,17 +261,40 @@ func (v *HLSVariant) getScalingString() string {
 // Video Quality
 
 // SetVideoBitrate will set the output bitrate of this variant's video
-func (v *HLSVariant) SetVideoBitrate(bitrate string) {
+func (v *HLSVariant) SetVideoBitrate(bitrate int) {
 	v.videoBitrate = bitrate
 }
 
-func (v *HLSVariant) getVideoQualityString() string {
+func (v *HLSVariant) getVideoQualityString(t *Transcoder) string {
 	if v.isVideoPassthrough {
 		return fmt.Sprintf("-map v:0 -c:v:%d copy", v.index)
 	}
 
 	encoderCodec := "libx264"
-	return fmt.Sprintf("-map v:0 -c:v:%d %s -b:v:%d %s", v.index, encoderCodec, v.index, v.videoBitrate)
+
+	// -1 to work around segments being generated slightly larger than expected.
+	// https://trac.ffmpeg.org/ticket/6915?replyto=58#comment:57
+	gop := (t.segmentLengthSeconds * v.framerate) - 1
+
+	// For limiting the output bitrate
+	// https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
+	// https://developer.apple.com/documentation/http_live_streaming/about_apple_s_http_live_streaming_tools
+	// Adjust the max & buffer size until the output bitrate doesn't exceed the ~+10% that Apple's media validator
+	// complains about.
+	maxBitrate := int(float64(v.videoBitrate) * 1.06) // Max is a ~+10% over specified bitrate.
+	bufferSize := int(float64(v.videoBitrate) * 1.2)  // How often it checks the bitrate of encoded segments to see if it's too high/low.
+
+	cmd := []string{
+		"-map v:0",
+		fmt.Sprintf("-c:v:%d %s", v.index, encoderCodec),                                                      // Video codec used for this variant
+		fmt.Sprintf("-b:v:%d %dk", v.index, v.videoBitrate),                                                   // The average bitrate for this variant
+		fmt.Sprintf("-maxrate:v:%d %dk", v.index, maxBitrate),                                                 // The max bitrate allowed for this variant
+		fmt.Sprintf("-bufsize:v:%d %dk", v.index, bufferSize),                                                 // How often the encoder checks the bitrate in order to meet average/max values
+		fmt.Sprintf("-g:v:%d %d", v.index, gop),                                                               // How often i-frames are encoded into the segments
+		fmt.Sprintf("-x264-params:v:%d \"scenecut=0:open_gop=0:min-keyint=%d:keyint=%d\"", v.index, gop, gop), // How often i-frames are encoded into the segments
+	}
+
+	return strings.Join(cmd, " ")
 }
 
 // SetVideoFramerate will set the output framerate of this variant's video

core/ffmpeg/transcoder_test.go

@@ -13,7 +13,7 @@ func TestFFmpegCommand(t *testing.T) {
 	transcoder.SetHLSPlaylistLength(10)
 
 	variant := HLSVariant{}
-	variant.videoBitrate = "1200k"
+	variant.videoBitrate = 1200
 	variant.isAudioPassthrough = true
 	variant.encoderPreset = "veryfast"
 	variant.SetVideoFramerate(30)
@@ -22,7 +22,7 @@ func TestFFmpegCommand(t *testing.T) {
 
 	cmd := transcoder.getString()
 
-	expected := "cat fakecontent.flv | /fake/path/ffmpeg -hide_banner -i pipe:  -map v:0 -c:v:0 libx264 -b:v:0 1200k -map a:0 -c:a:0 copy -r 30 -g 60 -keyint_min 60 -preset veryfast  -var_stream_map \"v:0,a:0 \" -f hls -hls_time 4 -hls_list_size 10 -hls_delete_threshold 10 -hls_flags delete_segments+program_date_time+temp_file -tune zerolatency -sc_threshold 0 -master_pl_name stream.m3u8 -strftime 1 -hls_segment_filename fakeOutput/%v/stream-%s.ts -max_muxing_queue_size 400 fakeOutput/%v/stream.m3u8 2> transcoder.log"
+	expected := `cat fakecontent.flv | /fake/path/ffmpeg -hide_banner -i pipe:  -map v:0 -c:v:0 libx264 -b:v:0 1200k -maxrate:v:0 1272k -bufsize:v:0 1440k -g:v:0 119 -x264-params:v:0 "scenecut=0:open_gop=0:min-keyint=119:keyint=119" -map a:0 -c:a:0 copy -r 30 -preset veryfast  -var_stream_map "v:0,a:0 " -f hls -hls_time 4 -hls_list_size 10 -hls_delete_threshold 10 -hls_flags delete_segments+program_date_time+temp_file -tune zerolatency -sc_threshold 0 -master_pl_name stream.m3u8 -strftime 1 -hls_segment_filename fakeOutput/%v/stream-%s.ts -max_muxing_queue_size 400 fakeOutput/%v/stream.m3u8 2> transcoder.log`
 
 	if cmd != expected {
 		t.Errorf("ffmpeg command does not match expected.  Got %s, want: %s", cmd, expected)