How to combine multiple Audio Files into single using ffmpeg_kit_flutter

Question

I want to play multiple Audio files in a sequence to form a question for the users.
For that, I tried the AudioPlay package in the loop but they took some pause to play it in between which did not look good.

So as the alternative I want to combine audio files into a single file to play.
For that I have used ffmpeg_kit_flutter package, but this returns 1 which means error in merging the files.

List<String> assetAudioFiles = [
  'audio/S1B_1.mp3', // Replace with the URLs or local paths of your audio files
  'audio/L2_31.mp3',
  'audio/S1B_2.mp3',
  'audio/L1s20.mp3',
];

Future<List<String>> copyAssetFilesToStorage() async {
  List<String> localFilePaths = [];

  for (String assetFile in assetAudioFiles) {
    String localFilePath = await copyAssetToFile(assetFile);
    localFilePaths.add(localFilePath);
  }

  return localFilePaths;
}
 
Future<String> copyAssetToFile(String assetFilePath) async {
  final ByteData data = await rootBundle.load(assetFilePath);
  final Directory tempDir = await getTemporaryDirectory();
  final File tempFile =
    File('${tempDir.path}/${assetFilePath.split('/').last}');
  await tempFile.writeAsBytes(data.buffer.asUint8List(), flush: true);
  return tempFile.path;
}
 
Future<void> combineAudio(List<String> audioFiles) async {
  Directory tempDir = await getTemporaryDirectory();
  String tempPath = tempDir.path;

  // Create a temporary output file path
  String combinedAudioPath = '$tempPath/output.mp3';

  // Prepare the FFmpeg command to concatenate audio files
  String inputFiles = audioFiles.join('|');

  String command =
    'ffmpeg -i "concat:$inputFiles" -acodec copy $combinedAudioPath';

  var cmd2 =
    "-i ${audioFiles[0]} -i ${audioFiles[1]} -i ${audioFiles[2]} -filter_complex [0:0][1:0][2:0]concat=n=3:v=0:a=1[out] -map [out] $combinedAudioPath";
     
  FFmpegKit.execute(cmd2).then((session) async {
    print('session $session');
    final returnCode = await session.getReturnCode();
    print('returnCode $returnCode');

    if (ReturnCode.isSuccess(returnCode)) {
     print('Audio files merged successfully $returnCode');
     // SUCCESS
    } else if (ReturnCode.isCancel(returnCode)) {
     print('isCancel $returnCode');
     // CANCEL
    } else {`enter code here`
     print('Error merging audio files: $returnCode');
     // audioPlayer.play(DeviceFileSource(outputFilePath));
    }
  });
}
  
void combineAndPlayAudio() async {
  List<String> localFilePaths = await copyAssetFilesToStorage();
  await combineAudio(localFilePaths); //localFilePaths

  // Now you can play the combined audio using an audio player or other methods.
}

So can you please let me know how to combine multiple audio files into single or a way to play multiple audio in sequence?

Answer 1

Here the code that I'm using the to concat multiple audios into one file,

• s.ptath, is the path of the audio

-combinedAudioPath is the path of the ouputAudio Please let me know if you need any help

String inputs = segments.map((s) => "-i '${s.path}'").join(" ");
        
String concatFilter = "concat=n=${segments.length}:v=0:a=1[aout]";

String mapArgs = "-map [aout]";

String command ='$inputs -filter_complex $concatFilter -threads 0 $mapArgs "$combinedAudioPath"';

await FFmpegKit.execute(command);