How to Convert PCM Samples in a Byte Array to Floating-Point Numbers Ranging from -1.0 to 1.0 and Vice Versa?

How can I convert PCM samples stored in a byte array to floating-point values within the range of -1.0 to 1.0 and then convert them back to PCM samples?

// Example Code to Convert PCM Bytes to Float
public static float[] convertPCMToFloat(byte[] pcmBytes) {
    int totalSamples = pcmBytes.length / 2;
    float[] floatArray = new float[totalSamples];

    for (int i = 0; i < totalSamples; i++) {
        // Convert bytes to short
        short sample = (short) ((pcmBytes[i * 2] & 0xFF) | (pcmBytes[i * 2 + 1] << 8));
        // Scale to float, from -1.0 to 1.0
        floatArray[i] = sample / 32768.0f;
    }
    return floatArray;
}

This guide explains the process of converting PCM (Pulse Code Modulation) samples stored in a byte array to floating-point numbers that fall within the range of -1.0 to 1.0. Additionally, we will cover how to convert these float values back to PCM samples. This conversion is critical for audio processing in various applications, including digital signal processing and audio effects.

// Code to Convert Float Back to PCM Bytes
public static byte[] convertFloatToPCM(float[] floatArray) {
    byte[] pcmBytes = new byte[floatArray.length * 2];

    for (int i = 0; i < floatArray.length; i++) {
        // Scale float to short
        short sample = (short) (floatArray[i] * 32768);
        pcmBytes[i * 2] = (byte) (sample & 0xFF);
        pcmBytes[i * 2 + 1] = (byte) ((sample >> 8) & 0xFF);
    }
    return pcmBytes;
}

Causes

• Understanding PCM format and bit depth (usually 16-bit) is essential for proper conversion.
• Improper handling of audio data can lead to distortion or data loss.
• Incorrect scaling factors can affect the audio playback quality.

Solutions

• To convert PCM data to floats, read bytes as signed shorts and scale them to the range of -1.0 to 1.0.
• For converting floats back to PCM, multiply the float values by 32768 to revert to the 16-bit signed integer range and handle byte conversion properly.

Mistake: Not converting between signed and unsigned values correctly.

Solution: Ensure you're using correct bit masking when converting between byte and short types.

Mistake: Overlooking potential precision loss when casting from float to byte.

Solution: Use proper scaling and clamping techniques to prevent distortion.

Mistake: Assuming all PCM values are 16-bit without checking.

Solution: Always confirm the bit depth of your PCM format before conversion.