Add ffmpeg version checker

internal/ffmpeg/ffmpeg.go

@@ -28,6 +28,9 @@ func Init() {
 	}
 
 	streams.RedirectFunc("ffmpeg", func(url string) (string, error) {
+		if _, err := Version(); err != nil {
+			return "", err
+		}
 		args := parseArgs(url[7:])
 		if slices.Contains(args.Codecs, "auto") {
 			return "", nil // force call streams.HandleFunc("ffmpeg")
@@ -46,7 +49,7 @@ var defaults = map[string]string{
 	"global": "-hide_banner",
 
 	// inputs
-	"file": "-re -i {input}",
+	"file": "-re -readrate_initial_burst 0.001 -i {input}",
 	"http": "-fflags nobuffer -flags low_delay -i {input}",
 	"rtsp": "-fflags nobuffer -flags low_delay -timeout 5000000 -user_agent go2rtc/ffmpeg -rtsp_flags prefer_tcp -i {input}",
 

internal/ffmpeg/version.go

@@ -0,0 +1,68 @@
+package ffmpeg
+
+import (
+	"bytes"
+	"errors"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"github.com/rs/zerolog/log"
+)
+
+var checkMu sync.Mutex
+var checkErr error
+var checkVer string
+
+const (
+	FFmpeg50 = "59. 16"
+	FFmpeg51 = "59. 27"
+	FFmpeg60 = "60.  3"
+	FFmpeg61 = "60. 16"
+	FFmpeg70 = "61.  1"
+)
+
+func Version() (string, error) {
+	checkMu.Lock()
+	defer checkMu.Unlock()
+
+	if checkVer != "" {
+		return checkVer, checkErr
+	}
+
+	cmd := exec.Command(defaults["bin"], "-version")
+	b, err := cmd.Output()
+	if err != nil {
+		checkVer = "-"
+		checkErr = err
+		return checkVer, checkErr
+	}
+
+	if len(b) < 100 {
+		checkVer = "?"
+		return checkVer, nil
+	}
+
+	// ffmpeg version n7.0-30-g8b0fe91754-20240520 Copyright (c) 2000-2024 the FFmpeg developers
+	b = b[15:]
+	if i := bytes.IndexByte(b, ' '); i > 0 {
+		checkVer = string(b[:i])
+	}
+
+	// libavformat    60. 16.100 / 60. 16.100
+	if i := strings.Index(string(b), "libavformat"); i > 0 {
+		// better to compare libavformat, because nightly/master builds
+		libav := string(b[i+15 : i+25])
+		if libav < FFmpeg50 {
+			checkErr = errors.New("ffmpeg: unsupported version: " + checkVer)
+			return checkVer, checkErr
+		}
+		if libav < FFmpeg61 && strings.Contains(defaults["file"], "readrate_initial_burst") {
+			defaults["file"] = "-re -i {input}"
+		}
+	}
+
+	log.Debug().Str("version", checkVer).Msgf("[ffmpeg] bin")
+
+	return checkVer, nil
+}