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androidaudioplayback

Playing audio backwards

Hi I'd like to play audio backwards in Android. How do I accomplish it? Any pointers will be appreciated. Thanks.

Solution

  • there probably isn't a functionality in the apis for this.

    however, it's quite easy to play pcm audio data backwards.

    a demonstration using c++ style pseudo-code:

    /* assuming 1 channel (mono), 16 bit LPCM */
const int16_t* const audioFileBuffer = audioFile.audioBuffer();

/* forward */
for (int idx = 0, sampleCount = audioFile.sampleCount(); idx < sampleCount; ++idx) {
    outputBuffer[idx] = audioFileBuffer[idx];
}

/* reverse */
for (int idx = 0, sampleCount = audioFile.sampleCount(), read = audioFile.sampleCount() - 1; idx < sampleCount; ++idx, --read) {
    outputBuffer[idx] = audioFileBuffer[read];
}