Real time pitch shift using Superpowered Android

Question

I am having problem in using the Superpowered time stretching function for real time pitch shift.

I have used this solution for my purpose. The problem is I am applying the change on the input buffer which is a short array and getting back noise after processing the buffer.

Here's the relevant code--

static bool audioProcessing(void * __unused clientdata, short int *audioInputOutput, int numberOfSamples, int __unused samplerate) {

        SuperpoweredAudiopointerList *outputBuffers = new SuperpoweredAudiopointerList(8, 16);

        // Create an input buffer for the time stretcher.
        SuperpoweredAudiobufferlistElement inputBuffer;
        inputBuffer.samplePosition = 0;
        inputBuffer.startSample = 0;
        inputBuffer.samplesUsed = 0;
        inputBuffer.endSample = numberOfSamples; // <-- Important!
        inputBuffer.buffers[0] = SuperpoweredAudiobufferPool::getBuffer(
                (unsigned int) (numberOfSamples * 8 + 64));
        inputBuffer.buffers[1] = inputBuffer.buffers[2] = inputBuffer.buffers[3] = NULL;

        // Convert the decoded PCM samples from 16-bit integer to 32-bit floating point.
        SuperpoweredShortIntToFloat(audioInputOutput, (float *)inputBuffer.buffers[0],
                                    (unsigned int) numberOfSamples);

        // Time stretching.
        timeStretch->process(&inputBuffer, outputBuffers);

        // Do we have some output?
        if (outputBuffers->makeSlice(0, outputBuffers->sampleLength)) {

            while (true) { // Iterate on every output slice.
                // Get pointer to the output samples.

                int _numSamples = 0;
                float *timeStretchedAudio = (float *)outputBuffers->nextSliceItem(&_numSamples);
                if (!timeStretchedAudio) break;

                SuperpoweredFloatToShortInt(timeStretchedAudio, audioInputOutput,
                                            (unsigned int) numberOfSamples);

            };

            // Clear the output buffer list.
            outputBuffers->clear();
        }

        return true;
    }

This is the audio processing function of the SuperpoweredAndroidAudioIO. I have defined the timeStretch in the initializing function.I am stuck at this point and need some help...

Thanks.

I think this reference involves every answer related to `Audio_Processing` whether it is *Pre-Processing* or *Post-Processing*: [Android_Audio_Processing_Using_WebRTC](https://github.com/mail2chromium/Android-Audio-Processing-Using-WebRTC), You can also visit this reference: https://stackoverflow.com/a/58546599/10413749 — Muhammad Usman Bashir, Apr 07 '20 at 08:48

score 0 · Answer 1 · answered Apr 10 '18 at 08:26

0

outputBuffers->makeSlice should ask for "numberOfSamples", not the entire "sampleLength". Also, when you put those samples into "audioInputOutput" in that iteration, make sure that "audioInputOutput" is also stepped, otherwise you will overwrite the same region (the beginning).

answered Apr 10 '18 at 08:26

Gabor Szanto

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putting "_numSamples" samples in "audioInputOutput" and increasing it by "_numsamples" inside the while loop. But no pitch shift is heard. – pR0 Apr 10 '18 at 09:52
output is stereo, increasing by _numsamples is just 1 channel – Gabor Szanto Apr 11 '18 at 09:33

Real time pitch shift using Superpowered Android

1 Answers1