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Tweak video bandwidth values to be < 10% over max

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This commit is contained in:
Gabe Kangas 2021-10-31 23:00:11 -07:00
parent aeaf886855
commit 5b38426e31
2 changed files with 31 additions and 19 deletions
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4
core/transcoder/codecs.go
View File

@ -67,11 +67,9 @@ func (c *Libx264Codec) ExtraFilters() string {
// VariantFlags returns a string representing a single variant processed by this codec.
func (c *Libx264Codec) VariantFlags(v *HLSVariant) string {
bufferSize := int(float64(v.videoBitrate) * 1.2) // How often it checks the bitrate of encoded segments to see if it's too high/low.
return strings.Join([]string{
fmt.Sprintf("-x264-params:v:%d \"scenecut=0:open_gop=0\"", v.index), // How often the encoder checks the bitrate in order to meet average/max values
fmt.Sprintf("-bufsize:v:%d %dk", v.index, bufferSize),
fmt.Sprintf("-bufsize:v:%d %dk", v.index, v.getBufferSize()),
fmt.Sprintf("-profile:v:%d %s", v.index, "high"), // Encoding profile
}, " ")
}

46
core/transcoder/transcoder.go
View File

@ -60,6 +60,28 @@ type VideoSize struct {
Height int
}
// 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.
// getAllocatedVideoBitrate returns the video bitrate we allocate after making some room for audio.
// 192 is pretty average.
func (v *HLSVariant) getAllocatedVideoBitrate() int {
return int(float64(v.videoBitrate) - 192)
}
// getMaxVideoBitrate returns the maximum video bitrate we allow the encoder to support.
func (v *HLSVariant) getMaxVideoBitrate() int {
return int(float64(v.getAllocatedVideoBitrate()) + float64(v.getAllocatedVideoBitrate())*0.07)
}
// getBufferSize returns how often it checks the bitrate of encoded segments to see if it's too high/low.
func (v *HLSVariant) getBufferSize() int {
return int(float64(v.getAllocatedVideoBitrate()) * 0.5)
}
// getString returns a WxH formatted getString for scaling video output.
func (v *VideoSize) getString() string {
widthString := strconv.Itoa(v.Width)
@ -132,7 +154,7 @@ func (t *Transcoder) Start() {
}
func (t *Transcoder) getString() string {
var port = t.internalListenerPort
port := t.internalListenerPort
localListenerAddress := "http://127.0.0.1:" + port
hlsOptionFlags := []string{}
@ -279,8 +301,8 @@ func (v *HLSVariant) getVariantString(t *Transcoder) string {
// Get the command flags for the variants.
func (t *Transcoder) getVariantsString() string {
var variantsCommandFlags = ""
var variantsStreamMaps = " -var_stream_map \""
variantsCommandFlags := ""
variantsStreamMaps := " -var_stream_map \""
for _, variant := range t.variants {
variantsCommandFlags = variantsCommandFlags + " " + variant.getVariantString(t)
@ -324,21 +346,13 @@ func (v *HLSVariant) getVideoQualityString(t *Transcoder) string {
}
gop := v.framerate * t.currentLatencyLevel.SecondsPerSegment // force an i-frame every segment
// 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.
cmd := []string{
"-map v:0",
fmt.Sprintf("-c:v:%d %s", v.index, t.codec.Name()), // 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("-g:v:%d %d", v.index, gop), // Suggested interval where i-frames are encoded into the segments
fmt.Sprintf("-keyint_min:v:%d %d", v.index, gop), // minimum i-keyframe interval
fmt.Sprintf("-c:v:%d %s", v.index, t.codec.Name()), // Video codec used for this variant
fmt.Sprintf("-b:v:%d %dk", v.index, v.getAllocatedVideoBitrate()), // The average bitrate for this variant allowing space for audio
fmt.Sprintf("-maxrate:v:%d %dk", v.index, v.getMaxVideoBitrate()), // The max bitrate allowed for this variant
fmt.Sprintf("-g:v:%d %d", v.index, gop), // Suggested interval where i-frames are encoded into the segments
fmt.Sprintf("-keyint_min:v:%d %d", v.index, gop), // minimum i-keyframe interval
fmt.Sprintf("-r:v:%d %d", v.index, v.framerate),
t.codec.VariantFlags(v),
}