/*
* All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
* its licensors.
*
* For complete copyright and license terms please see the LICENSE at the root of this
* distribution (the "License"). All use of this software is governed by the License,
* or, if provided, by the license below or the license accompanying this file. Do not
* remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*
*/

#include "Microphone_precompiled.h"

#include "SimpleDownsample.h"

#include <cmath>

AZStd::size_t GetDownsampleSize(AZStd::size_t sourceSize, AZ::u32 sourceSampleRate, AZ::u32 targetSampleRate)
{
	return (AZStd::size_t)round((float)sourceSize / ((float)sourceSampleRate / (float)targetSampleRate));
}

void Downsample(AZ::s16* inBuffer, AZStd::size_t inBufferSize, AZ::u32 inBufferSampleRate,
				AZ::s16* outBuffer, AZStd::size_t outBufferSize, AZ::u32 outBufferSampleRate)
{
	if(inBufferSampleRate == outBufferSampleRate)
	{
		return;	// nothing to do here!
	}

	if(inBufferSampleRate < outBufferSampleRate)
	{
		AZ_Error("SimpleDownsample", false, "Out buffer sample rate is higher than in buffer sample rate, must be lower");
		return;
	}

	float sampleRateRatio = (float)inBufferSampleRate / (float)outBufferSampleRate;
	AZStd::size_t offsetResult = 0;
	AZStd::size_t offsetBuffer = 0;
	while(offsetResult < outBufferSize)
	{
		AZStd::size_t nextOffsetBuffer = static_cast<AZStd::size_t>(round((float)(offsetResult + 1) * sampleRateRatio));
		AZ::s32 accum = 0;	// this must be int 32 so it doesn't overflow with multiple int 16's possibly at max
		AZStd::size_t count = 0;
		for(AZStd::size_t i = offsetBuffer; i < nextOffsetBuffer && i < inBufferSize; ++i)
		{
			accum += inBuffer[i];
			count++;
		}
		// do the math in floating point then convert to signed 16
		outBuffer[offsetResult] = (AZ::s16)((float)accum / (float)count);
		offsetResult++;
		offsetBuffer = nextOffsetBuffer;
	}
}