Android AAudioStream_write
Android AAudio is a low latency audio API introduced in Android 8.0 (API level 26). It provides a simplified and efficient way to write audio data to the audio output stream. In this article, we will explore the AAudioStream_write function and how to use it in an Android application.
AAudioStream_write Function
The AAudioStream_write function is used to write audio data to the output stream. It takes the following parameters:
- aaudio_stream: A pointer to the AAudioStream object representing the output stream.
- buffer: A pointer to the audio data buffer to be written.
- numFrames: The number of frames to be written.
- timeoutNanoseconds: The maximum time to wait for the write operation to complete.
The function returns the number of frames actually written, which may be less than the requested number of frames.
Example
Let's consider an example where we want to generate a sine wave audio and write it to the output stream using AAudioStream_write.
First, we need to create and open the AAudioStream object. We can use the AAudioBuilder class to simplify this process:
// Create an AAudioBuilder object
AAudioStreamBuilder builder = new AAudioStreamBuilder();
// Set the desired audio format, sample rate, and channel count
builder.setFormat(AudioFormat.ENCODING_PCM_16BIT)
.setSampleRate(44100)
.setChannelCount(2);
// Open the AAudioStream
AAudioStream stream = builder.build();
stream.open();
Next, we need to generate the audio data. In this example, we will generate a sine wave using the formula amplitude * sin(2 * pi * frequency * time):
double amplitude = Short.MAX_VALUE;
double frequency = 440.0;
double sampleRate = stream.getSampleRate();
short[] buffer = new short[stream.getBufferCapacityInFrames() * stream.getChannelCount()];
double time = 0.0;
for (int i = 0; i < buffer.length; i += stream.getChannelCount()) {
double value = amplitude * Math.sin(2 * Math.PI * frequency * time);
buffer[i] = (short) value;
buffer[i + 1] = (short) value;
time += 1.0 / sampleRate;
}
Finally, we can write the audio data to the output stream using the AAudioStream_write function:
int numFramesWritten = stream.write(buffer, buffer.length, 0);
It is important to note that the AAudioStream_write function may not write the requested number of frames due to various reasons such as buffer size limits or timeout. Therefore, it is recommended to check the return value to ensure the desired number of frames are written.
Conclusion
In this article, we have explored the Android AAudioStream_write function and how to use it to write audio data to the output stream. We have also provided a code example for generating a sine wave audio and writing it to the stream. By understanding and utilizing the AAudio API, developers can achieve low-latency and high-quality audio playback on Android devices.
