ppsspp/ios/iOSCoreAudio.mm

// Copyright (c) 2012- PPSSPP Project.

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 2.0 or later versions.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
// GNU General Public License 2.0 for more details.

// A copy of the GPL 2.0 should have been included with the program.
// If not, see http://www.gnu.org/licenses/

// Official git repository and contact information can be found at
// https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.

// This code implements the emulated audio using CoreAudio for iOS
// Originally written by jtraynham

#include "iOSCoreAudio.h"

#include "Common/Log.h"

#include <AudioToolbox/AudioToolbox.h>
#import <AVFoundation/AVFoundation.h>


#define SAMPLE_RATE 44100

AudioComponentInstance audioInstance = nil;

int NativeMix(short *audio, int num_samples);

OSStatus iOSCoreAudioCallback(void *inRefCon,
							  AudioUnitRenderActionFlags *ioActionFlags,
							  const AudioTimeStamp *inTimeStamp,
							  UInt32 inBusNumber,
							  UInt32 inNumberFrames,
							  AudioBufferList *ioData)
{
	// see if we have any sound to play
	short *output = (short *)ioData->mBuffers[0].mData;
	UInt32 framesReady = NativeMix(output, inNumberFrames);
	
	if (framesReady == 0) {
		// oops, we don't currently have any sound, so return silence
		*ioActionFlags |= kAudioUnitRenderAction_OutputIsSilence;
	}
	
	/* 
	 * You'd think iOS would want to know how many frames were
	 * actually generated in case it was less than asked for, but
	 * apparently that causes micro-stuttering and everything just
	 * works better if we lie and say we successfully generated as
	 * many frames as it wanted... weird. We still get micro-stuttering
	 * but it's less noticeable this way.
	 */ 
	//UInt32 bytesReady = framesReady * sizeof(short) * 2;
	UInt32 bytesReady = inNumberFrames * sizeof(short) * 2;
	ioData->mBuffers[0].mDataByteSize = bytesReady;
	
	return noErr;
}

void iOSCoreAudioInit()
{
	NSError *error = nil;
	AVAudioSession *session = [AVAudioSession sharedInstance];
	if (![session setActive:YES error:&error]) {
		ERROR_LOG(SYSTEM, "Failed to activate AVFoundation audio session");
		if (error.localizedDescription) {
			NSLog(@"%@", error.localizedDescription);
		}
		if (error.localizedFailureReason) {
			NSLog(@"%@", error.localizedFailureReason);
		}
	}
	
	if (!audioInstance) {
		OSErr err;
		
		// first, grab the default output
		AudioComponentDescription defaultOutputDescription;
		defaultOutputDescription.componentType = kAudioUnitType_Output;
		defaultOutputDescription.componentSubType = kAudioUnitSubType_RemoteIO;
		defaultOutputDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
		defaultOutputDescription.componentFlags = 0;
		defaultOutputDescription.componentFlagsMask = 0;
		AudioComponent defaultOutput = AudioComponentFindNext(NULL, &defaultOutputDescription);
		
		// create our instance
		err = AudioComponentInstanceNew(defaultOutput, &audioInstance);
		if (err != noErr) {
			audioInstance = nil;
			return;
		}
		
		// create our callback so we can give it the audio data
		AURenderCallbackStruct input;
		input.inputProc = iOSCoreAudioCallback;
		input.inputProcRefCon = NULL;
		err = AudioUnitSetProperty(audioInstance,
								   kAudioUnitProperty_SetRenderCallback,
								   kAudioUnitScope_Input,
								   0,
								   &input,
								   sizeof(input));
		if (err != noErr) {
			AudioComponentInstanceDispose(audioInstance);
			audioInstance = nil;
			return;
		}
		
		// setup the audio format we'll be using (stereo pcm)
		AudioStreamBasicDescription streamFormat;
		memset(&streamFormat, 0, sizeof(streamFormat));
		streamFormat.mSampleRate = SAMPLE_RATE;
		streamFormat.mFormatID = kAudioFormatLinearPCM;
		streamFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
		streamFormat.mBitsPerChannel = sizeof(short) * 8;
		streamFormat.mChannelsPerFrame = 2;
		streamFormat.mFramesPerPacket = 1;
		streamFormat.mBytesPerFrame = (streamFormat.mBitsPerChannel / 8) * streamFormat.mChannelsPerFrame;
		streamFormat.mBytesPerPacket = streamFormat.mBytesPerFrame * streamFormat.mFramesPerPacket;
		err = AudioUnitSetProperty(audioInstance,
								   kAudioUnitProperty_StreamFormat,
								   kAudioUnitScope_Input,
								   0,
								   &streamFormat,
								   sizeof(AudioStreamBasicDescription));
		if (err != noErr) {
			AudioComponentInstanceDispose(audioInstance);
			audioInstance = nil;
			return;
		}
		
		// k, all setup, so init
		err = AudioUnitInitialize(audioInstance);
		if (err != noErr) {
			AudioComponentInstanceDispose(audioInstance);
			audioInstance = nil;
			return;
		}
		
		// finally start playback
		err = AudioOutputUnitStart(audioInstance);
		if (err != noErr) {
			AudioUnitUninitialize(audioInstance);
			AudioComponentInstanceDispose(audioInstance);
			audioInstance = nil;
			return;
		}
		
		// we're good to go
	}
}

void iOSCoreAudioShutdown()
{
	if (audioInstance) {
		AudioOutputUnitStop(audioInstance);
		AudioUnitUninitialize(audioInstance);
		AudioComponentInstanceDispose(audioInstance);
		audioInstance = nil;
	}
}