install go2rtc on bob

installs_on_host/go2rtc/pkg/ffmpeg/ffmpeg.go

@@ -0,0 +1,123 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"strconv"
+	"strings"
+)
+
+// correlation of libavformat versions with ffmpeg versions
+const (
+	Version50 = "59. 16"
+	Version51 = "59. 27"
+	Version60 = "60.  3"
+	Version61 = "60. 16"
+	Version70 = "61.  1"
+)
+
+type Args struct {
+	Bin     string   // ffmpeg
+	Global  string   // -hide_banner -v error
+	Input   string   // -re -stream_loop -1 -i /media/bunny.mp4
+	Codecs  []string // -c:v libx264 -g:v 30 -preset:v ultrafast -tune:v zerolatency
+	Filters []string // scale=1920:1080
+	Output  string   // -f rtsp {output}
+	Version string   // libavformat version, it's more reliable than the ffmpeg version
+
+	Video, Audio int // count of Video and Audio params
+}
+
+func (a *Args) AddCodec(codec string) {
+	a.Codecs = append(a.Codecs, codec)
+}
+
+func (a *Args) AddFilter(filter string) {
+	a.Filters = append(a.Filters, filter)
+}
+
+func (a *Args) InsertFilter(filter string) {
+	a.Filters = append([]string{filter}, a.Filters...)
+}
+
+func (a *Args) HasFilters(filters ...string) bool {
+	for _, f1 := range a.Filters {
+		for _, f2 := range filters {
+			if strings.HasPrefix(f1, f2) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func (a *Args) String() string {
+	b := bytes.NewBuffer(make([]byte, 0, 512))
+
+	b.WriteString(a.Bin)
+
+	if a.Global != "" {
+		b.WriteByte(' ')
+		b.WriteString(a.Global)
+	}
+
+	b.WriteByte(' ')
+	// starting from FFmpeg 6.1 readrate=1 has default initial bust 0.5 sec
+	// it might make us miss the first couple seconds of the file
+	if strings.HasPrefix(a.Input, "-re ") && a.Version >= Version61 {
+		b.WriteString("-readrate_initial_burst 0.001 ")
+	}
+	b.WriteString(a.Input)
+
+	multimode := a.Video > 1 || a.Audio > 1
+	var iv, ia int
+
+	for _, codec := range a.Codecs {
+		// support multiple video and/or audio codecs
+		if multimode && len(codec) >= 5 {
+			switch codec[:5] {
+			case "-c:v ":
+				codec = "-map 0:v:0? " + strings.ReplaceAll(codec, ":v ", ":v:"+strconv.Itoa(iv)+" ")
+				iv++
+			case "-c:a ":
+				codec = "-map 0:a:0? " + strings.ReplaceAll(codec, ":a ", ":a:"+strconv.Itoa(ia)+" ")
+				ia++
+			}
+		}
+
+		b.WriteByte(' ')
+		b.WriteString(codec)
+	}
+
+	if len(a.Filters) > 0 {
+		for i, filter := range a.Filters {
+			if i == 0 {
+				b.WriteString(` -vf "`)
+			} else {
+				b.WriteByte(',')
+			}
+			b.WriteString(filter)
+		}
+		b.WriteByte('"')
+	}
+
+	b.WriteByte(' ')
+	b.WriteString(a.Output)
+
+	return b.String()
+}
+
+func ParseVersion(b []byte) (ffmpeg string, libavformat string) {
+	if len(b) > 100 {
+		// ffmpeg version n7.0-30-g8b0fe91754-20240520 Copyright (c) 2000-2024 the FFmpeg developers
+		if i := bytes.IndexByte(b[15:], ' '); i > 0 {
+			ffmpeg = string(b[15 : 15+i])
+		}
+
+		// libavformat    60. 16.100 / 60. 16.100
+		if i := strings.Index(string(b), "libavformat"); i > 0 {
+			libavformat = string(b[i+15 : i+25])
+		}
+	}
+	return
+}