Check audio files for audio track

utils.go

@@ -2,6 +2,7 @@ package vidio
 
 import (
 	"errors"
+	"io"
 	"os"
 	"os/exec"
 	"regexp"
@@ -34,6 +35,45 @@ func checkExists(program string) {
 	}
 }
 
+// Runs ffprobe on the given file and returns a map of the metadata.
+func ffprobe(filename, stype string) map[string]string {
+	// "stype" is stream stype. "v" for video, "a" for audio.
+	// Extract video information with ffprobe.
+	cmd := exec.Command(
+		"ffprobe",
+		"-show_streams",
+		"-select_streams", stype, // Only show video data
+		"-print_format", "compact",
+		"-loglevel", "quiet",
+		filename,
+	)
+
+	pipe, err := cmd.StdoutPipe()
+	if err != nil {
+		panic(err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		panic(err)
+	}
+	// Read ffprobe output from Stdout.
+	buffer := make([]byte, 2<<10)
+	total := 0
+	for {
+		n, err := pipe.Read(buffer[total:])
+		total += n
+		if err == io.EOF {
+			break
+		}
+	}
+	// Wait for ffprobe command to complete.
+	if err := cmd.Wait(); err != nil {
+		panic(err)
+	}
+
+	return parseFFprobe(buffer[:total])
+}
+
 // Parse ffprobe output to fill in video data.
 func parseFFprobe(input []byte) map[string]string {
 	data := make(map[string]string)

video.go

@@ -29,52 +29,14 @@ type Video struct {
 // Uses ffprobe to get video information and fills in the Video struct with this data.
 func NewVideo(filename string) *Video {
 	if !exists(filename) {
-		panic("File: " + filename + " does not exist")
+		panic("Video file " + filename + " does not exist")
 	}
 	// Check if ffmpeg and ffprobe are installed on the users machine.
 	checkExists("ffmpeg")
 	checkExists("ffprobe")
 
-	ffprobe := func(stype string) map[string]string {
-		// "stype" is stream stype. "v" for video, "a" for audio.
-		// Extract video information with ffprobe.
-		cmd := exec.Command(
-			"ffprobe",
-			"-show_streams",
-			"-select_streams", stype, // Only show video data
-			"-print_format", "compact",
-			"-loglevel", "quiet",
-			filename,
-		)
-
-		pipe, err := cmd.StdoutPipe()
-		if err != nil {
-			panic(err)
-		}
-
-		if err := cmd.Start(); err != nil {
-			panic(err)
-		}
-		// Read ffprobe output from Stdout.
-		buffer := make([]byte, 2<<10)
-		total := 0
-		for {
-			n, err := pipe.Read(buffer[total:])
-			total += n
-			if err == io.EOF {
-				break
-			}
-		}
-		// Wait for ffprobe command to complete.
-		if err := cmd.Wait(); err != nil {
-			panic(err)
-		}
-
-		return parseFFprobe(buffer[:total])
-	}
-
-	videoData := ffprobe("v")
-	audioData := ffprobe("a")
+	videoData := ffprobe(filename, "v")
+	audioData := ffprobe(filename, "a")
 
 	video := &Video{filename: filename, depth: 3}
 

videowriter.go

@@ -93,8 +93,13 @@ func NewVideoWriter(filename string, width, height int, options *Options) *Video
 
 	if options.audio != "" {
 		if !exists(options.audio) {
-			panic("Audio file does not exist.")
+			panic("Audio file " + options.audio + " does not exist.")
 		}
+
+		if len(ffprobe(options.audio, "a")) == 0 {
+			panic("Given \"audio\" file " + options.audio + " has no audio.")
+		}
+
 		writer.audio = options.audio
 
 		if options.audio_codec == "" {