Question

I am using MediaRecorder in my Android app. I referred to the online documentation for the public void setOutputFile (String path) of the MediaRecorder class but couldn’t find information as to whether it overwrites an existing file at the same path or appends to the existing file, if it exists.

So, two questions:

1. Does public void setOutputFile (String path) overwrite the file at path, if it exists, or it appends to the file at path?
2. Is there any way to resume an already paused recording which is saved at a particular path?

Thanks in advance.

Answer 1

So far from my finding, I conclude that the Android API currently does not provide an option to resume recording using MediaRecorder.

So manage my target of merging two recorded audio, I went with direct merging of two files by skipping the headers from the second file.

Following is my code for reference:

    mRecorder = new MediaRecorder();
    mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    mRecorder.setOutputFormat(MediaRecorder.OutputFormat.RAW_AMR);

    /* If the voiceMessage in consideration is a PAUSED one, then we should 
     * record at a new alternate path so that earlier recording does not get overwritten, and can be used later for merging */
    Log.d(LOG_TAG, "VoiceMessageManager:recordVoiceMessage() - state of voice message - " + voiceMessage.getVoiceMessageState());

    mRecorder.setOutputFile(filePath);

    mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    mRecorder.prepare();
    mRecorder.start();

And my code for combining the two audio files is as follows:

protected Void doInBackground(String... filePaths) {
         try {
                String originalVoiceMessageRecording = filePaths[0];
                String newVoiceMessageRecording = filePaths[1];

                File outputFile = new File(originalVoiceMessageRecording);
                FileOutputStream fos = new FileOutputStream(outputFile, true); // Second parameter to indicate appending of data

                File inputFile = new File(newVoiceMessageRecording);
                FileInputStream fis = new FileInputStream(inputFile);

                Log.d(LOG_TAG, "Length of outputFile: " + outputFile.length() + " and Length of inputFile: " + inputFile.length() );

                byte fileContent[]= new byte[(int)inputFile.length()];
                fis.read(fileContent);// Reads the file content as byte from the list.

                /* copy the entire file, but not the first 6 bytes */
                byte[] headerlessFileContent = new byte[fileContent.length-6];
                for(int j=6; j<fileContent.length;j++){
                    headerlessFileContent[j-6] = fileContent[j];
                }
                fileContent = headerlessFileContent;

                /* Write the byte into the combine file. */
                fos.write(fileContent);

                /* Delete the new recording as it is no longer required (Save memory!!!) :-) */
                File file = new File(newVoiceMessageRecording); 
                boolean deleted = file.delete();

                Log.d(LOG_TAG, "New recording deleted after merging: " + deleted);
                Log.d(LOG_TAG, "Successfully merged the two Voice Message Recordings");
                Log.d(LOG_TAG, "Length of outputFile after merging: " + outputFile.length());
            } catch (Exception ex) {
                Log.e(LOG_TAG, "Error while merging audio file: " + ex.getMessage());
            }
        return null;
     }

In short what I am doing is – skipping the headers of the second file (The length of the header in AMR file is 6 bytes).

This worked for me and I tested it on Android version 2.3

Hope this helps others!