Develop Reference

How To Record Sound in Android with Better Quality and Reduce Noise

I’m trying to build a music analytics app for android platform.
the app is using MediaRecorder.AudioSource.MIC
to record the music form the MIC and them encode it PCM 16BIT with 11025 freq, but the recorded audio sample are very low quality is there any way to make it better, decrease the noise?
mRecordInstance = new AudioRecord(MediaRecorder.AudioSource.MIC,FREQUENCY, CHANNEL,ENCODING, minBufferSize);
mRecordInstance.startRecording();
do
{
samplesIn += mRecordInstance.read(audioData, samplesIn, bufferSize - samplesIn);
if(mRecordInstance.getRecordingState() == AudioRecord.RECORDSTATE_STOPPED)
break;
}
while (samplesIn < bufferSize);
Thanks in Advance

The solution above didnt work for me.
So, i searched around and found this article.
Long story short, I used MediaRecorder.AudioSource.VOICE_RECOGNITION instead of AudioSource.MIC, which gave me really good results and noise in the background did reduce very much.
The great thing about this solution is, it can be used with both AudioRecord and MediaRecorder class.

The best combination of SR and buffer size is very device dependant, so your results will vary depending on the hardware. I use this utility to figure out what the best combination is for devices running Android 4.2 and above;
public static DeviceValues getDeviceValues(Context context) {
try {
AudioManager am = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
try {
Method getProperty = AudioManager.class.getMethod("getProperty", String.class);
Field bufferSizeField = AudioManager.class.getField("PROPERTY_OUTPUT_FRAMES_PER_BUFFER");
Field sampleRateField = AudioManager.class.getField("PROPERTY_OUTPUT_SAMPLE_RATE");
int bufferSize = Integer.valueOf((String)getProperty.invoke(am, (String)bufferSizeField.get(am)));
int sampleRate = Integer.valueOf((String)getProperty.invoke(am, (String)sampleRateField.get(am)));
return new DeviceValues(sampleRate, bufferSize);
} catch(NoSuchMethodException e) {
return selectBestValue(getValidSampleRates(context));
}
} catch(Exception e) {
return new DeviceValues(DEFAULT_SAMPLE_RATE, DEFAULT_BUFFER_SIZE);
}
}
This uses reflection to check if the getProperty method is available, because this method was introduced in API level 17. If you are developing for a specific device type, you might want to experiment with various buffer sizes and sample rates. The defaults that I use as a fallback are;
private static final int DEFAULT_SAMPLE_RATE = 22050;
private static final int DEFAULT_BUFFER_SIZE = 1024;
Additionally I check the various SR by seeing if getMinBufferSize returns a reasonable value for use;
private static List<DeviceValues> getValidSampleRates(Context context) {
List<DeviceValues> available = new ArrayList<DeviceValues>();
for (int rate : new int[] {8000, 11025, 16000, 22050, 32000, 44100, 48000, 96000}) { // add the rates you wish to check against
int bufferSize = AudioRecord.getMinBufferSize(rate, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
if (bufferSize > 0 && bufferSize < 2048) {
available.add(new DeviceValues(rate, bufferSize * 2));
}
}
return available;
}
This depends on the logic that if getMinBufferSize returns 0, the sample rate is not available in the device. You should experiment with these values for your particular use case.

Though it is an old question following solution will be helpful.
We can use MediaRecorder to record audio with ease.
private void startRecording() {
MediaRecorder recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
recorder.setAudioEncodingBitRate(96000)
recorder.setAudioSamplingRate(44100)
recorder.setOutputFile(".../audioName.m4a");
try {
recorder.prepare();
} catch (IOException e) {
Log.e(LOG_TAG, "prepare() failed");
}
recorder.start();
}
Note:
MediaRecorder.AudioEncoder.AAC is used as MediaRecorder.AudioEncoder.AMR_NB encoding is no longer supported in iOS. Reference
AudioEncodingBitRate should be used either 96000 or 128000 as required for clarity of sound.

How to get pcm from fm radio source on android?

I try to get raw data in PCM format form fm radio source. I do this:
int bufSize = AudioRecord.getMinBufferSize(SAMPLE_RATE_16kHz, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT);
mRecorder = new AudioRecord(AudioSource.FM_RX, SAMPLE_RATE_16kHz, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT, bufSize);
mBuffer = new short[bufSize / 2];
mRecorder.startRecording();
and when I call in a loop:
int ret = mRecorder.read(mBuffer, 0, mBuffer.length);
the value in ret is 0 and buffer is empty.
But if I change AudioSource.FM_RX to AudioSource.MIC I can get data form microphone. What I do wrong?

AudioSource.FM_RX might be available via CyanogenMod but not in the standard API (see e.g. this question).

Audio Recording in Stereo giving same data in Left and Right channels

I am trying to record and process audio data based on differences in what gets recorded in the left and right channel. For this I am using Audio Record class, with MIC as input and STEREO mode.
recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRate,
AudioFormat.CHANNEL_IN_STEREO,
AudioFormat.ENCODING_PCM_16BIT, bufferSize);
My issue is that I get exactly the same data in both the channels. (alternate samples are separated to get individual channel inputs). Please help. I am not sure why this is happening.

Using this configuration:
private int audioSource = MediaRecorder.AudioSource.MIC;
private static int sampleRateInHz = 48000;
private static int channelConfig = AudioFormat.CHANNEL_IN_STEREO;
private static int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
The data in the audio data is as follows.
leftChannel data: [0,1],[4,5]...
rightChannel data: [2,3],[6,7]...
So you need to seperate the data.
readSize = audioRecord.read(audioShortData, 0, bufferSizeInBytes);
for(int i = 0; i < readSize/2; i = i + 2)
{
leftChannelAudioData[i] = audiodata[2*i];
leftChannelAudioData[i+1] = audiodata[2*i+1];
rightChannelAudioData[i] = audiodata[2*i+2];
rightChannelAudioData[i+1] = audiodata[2*i+3];
}
Hope this helpful.

Here is a working example for capturing audio in stereo (tested with Samsung Galaxy S3 4.4.2 SlimKat):
private void startRecording() {
String filename = Environment.getExternalStorageDirectory().getPath()+"/SoundRecords/"+System.currentTimeMillis()+".aac";
File record = new File(filename);
recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
recorder.setAudioEncodingBitRate(128000);
recorder.setAudioSamplingRate(96000);
recorder.setAudioChannels(2);
recorder.setOutputFile(filename);
t_filename.setText(record.getName());
try {
recorder.prepare();
recorder.start();
} catch (IOException e) {
e.printStackTrace();
}
}
If your phone supports stereo capturing, then this should work :)

You cannot obtain a stereo input in this way on your device.
Although the Nexus 4 has two microphones, they are not intended for stereo recording, but instead are likely for background noise cancellation.
See https://groups.google.com/forum/#!topic/android-platform/SptXI964eEI where various low-level modifications of the audio system are discussed in an attempt to accomplish stereo recording.

split two channels of AudioRecord of CHANNEL_IN_STEREO

I'm working on a project using stereo record of the Android phones (note 3). But I need to split the data from different channels (right, left). Any idea of how to perform that?
Now, I use AudioRecord to record the sound of internal microphones. And I can record, save the sound to .raw and .wav files.
Some codes as follows.
private int audioSource = MediaRecorder.AudioSource.MIC;
private static int sampleRateInHz = 44100;
private static int channelConfig = AudioFormat.CHANNEL_IN_STEREO;
private static int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
bufferSizeInBytes = AudioRecord.getMinBufferSize(sampleRateInHz,
channelConfig, audioFormat);
audioRecord = new AudioRecord(audioSource, sampleRateInHz,
channelConfig, audioFormat, bufferSizeInBytes);
// some other codes....
//get the data from audioRecord
readsize = audioRecord.read(audiodata, 0, bufferSizeInBytes);

Finally, I got the answers. I used stereo record of android phone. And the audioFormat is PCM_16BIT.
private int audioSource = MediaRecorder.AudioSource.MIC;
private static int sampleRateInHz = 48000;
private static int channelConfig = AudioFormat.CHANNEL_IN_STEREO;
private static int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
which means the data stored in buffer as follows.
leftChannel data: [0,1],[4,5]...
rightChannel data: [2,3],[6,7]...
So the code of splitting data of stereo record.
readSize = audioRecord.read(audioShortData, 0, bufferSizeInBytes);
for(int i = 0; i < readSize/2; i = i + 2)
{
leftChannelAudioData[i] = audiodata[2*i];
leftChannelAudioData[i+1] = audiodata[2*i+1];
rightChannelAudioData[i] = audiodata[2*i+2];
rightChannelAudioData[i+1] = audiodata[2*i+3];
}
Then you can write the data to file.
leftChannelFos = new FileOutputStream(rawLeftChannelDataFile);
rightChannelFos = new FileOutputStream(rawRightChannelDataFile);
leftChannelBos = new BufferedOutputStream(leftChannelFos);
rightChannelBos = new BufferedOutputStream(rightChannelFos);
leftChannelDos = new DataOutputStream(leftChannelBos);
rightChannelDos = new DataOutputStream(rightChannelBos);
leftChannelDos.write(leftChannelAudioData);
rightChannelDos.write(rightChannelAudioData);
Happy coding!

Why does AudioRecord.getMinBufferSize return ERROR_BAD_VALUE (-2)?

I am testing this on a Samsung Galaxy S i9000.
int sampleRate = 44100;
int bufferSize = AudioRecord.getMinBufferSize(sampleRate,
AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_8BIT);
It returns -2 ERROR_BAD_VALUE.
The native sample rate is 44100Hz, as returned by
AudioTrack.getNativeOutputSampleRate(AudioManager.STREAM_SYSTEM).
I have tried setting sampleRate to 1000, 8000, 22100 and 44100. I have also tried changing AudioFormat.CHANNEL_IN_MONO to AudioFormat.CHANNEL_CONFIGURATION_MONO. I have also tried STEREO (both IN_STEREO and CONFIGURATION_STEREO). I have also tried 16 bit encoding instead of 8 bit.
Update: my Manifest has AUDIO_RECORD as permission.
I keep getting -2 as a result. Why is this happening?

From the platform source file AudioRecord.java:
static public int getMinBufferSize(int sampleRateInHz, int channelConfig, int audioFormat) {
...
// PCM_8BIT is not supported at the moment
if (audioFormat != AudioFormat.ENCODING_PCM_16BIT) {
loge("getMinBufferSize(): Invalid audio format.");
return AudioRecord.ERROR_BAD_VALUE;
}
...
}
Looks like your choice is 16-bit or nothing. :\

In emulator it will always return -2. With the same code it will ok on real mobile.