converting all the mp4 audio files in a folder to mp3 using ffmpeg [duplicate]

Question

how can I convert all of the mp4 files in a given folder to mp3 using ffmpeg. Almost all of the links I have seen on google is all about converting mp4 video to mp3. I can do this via VLC player but I have got huge collection ~ 1000 mp4 audio files and want this to be done over command line by some script or command. Is it possible to do it via gstreamer?

Answer 1

One method is a bash for loop.

For converting only .mp4 files:

mkdir outputs
for f in *.mp4; do ffmpeg -i "$f" -c:a libmp3lame "outputs/${f%.mp4}.mp3"; done

For converting .m4a, .mov, and .flac:

mkdir outputs
for f in *.{m4a,mov,flac}; do ffmpeg -i "$f" -c:a libmp3lame "outputs/${f%.*}.mp3"; done

For converting anything use the "*" wildcard:

mkdir outputs
for f in *; do ffmpeg -i "$f" -c:a libmp3lame "outputs/${f%.*}.mp3"; done

Answer 2

FileInfo[] Files = d.GetFiles("*.mp4").Union(d.GetFiles("*.<any other file extension>")).ToArray(); 

foreach (FileInfo file in Files)
{
    // str = str + ", " + file.Name;
    builder.Append(Path.GetFileNameWithoutExtension(file.Name));

    ProcessStartInfo startInfo = new ProcessStartInfo();
    startInfo.CreateNoWindow = false;
    startInfo.UseShellExecute = false;
    startInfo.FileName = "ffmpeg.exe";
    startInfo.WindowStyle = ProcessWindowStyle.Hidden;
    startInfo.RedirectStandardOutput = !string.IsNullOrEmpty("test");
    startInfo.Arguments = "-i " + filename + ".mp4 -q:a 0 -map a " + filename + ".mp3";
}