How to convert m4a file to aac adts file in Xcode?
- by Bird Hsuie
I have a mp4 file copied from iPod lib and saved to my Document
for my next step, I need it to convert to .mp3 or .aac(ADTS type)
I use this code and failed...
-(IBAction)compressFile:(id)sender{
NSLog (@"handleConvertToPCMTapped");
// open an ExtAudioFile
NSLog (@"opening %@", exportURL);
ExtAudioFileRef inputFile;
CheckResult (ExtAudioFileOpenURL((__bridge CFURLRef)exportURL, &inputFile),
"ExtAudioFileOpenURL failed");
// prepare to convert to a plain ol' PCM format
AudioStreamBasicDescription myPCMFormat;
myPCMFormat.mSampleRate = 44100; // todo: or use source rate?
myPCMFormat.mFormatID = kAudioFormatMPEGLayer3 ;
myPCMFormat.mFormatFlags = kAudioFormatFlagsCanonical;
myPCMFormat.mChannelsPerFrame = 2;
myPCMFormat.mFramesPerPacket = 1;
myPCMFormat.mBitsPerChannel = 16;
myPCMFormat.mBytesPerPacket = 4;
myPCMFormat.mBytesPerFrame = 4;
CheckResult (ExtAudioFileSetProperty(inputFile, kExtAudioFileProperty_ClientDataFormat,
sizeof (myPCMFormat), &myPCMFormat),
"ExtAudioFileSetProperty failed");
// allocate a big buffer. size can be arbitrary for ExtAudioFile.
// you have 64 KB to spare, right?
UInt32 outputBufferSize = 0x10000;
void* ioBuf = malloc (outputBufferSize);
UInt32 sizePerPacket = myPCMFormat.mBytesPerPacket;
UInt32 packetsPerBuffer = outputBufferSize / sizePerPacket;
// set up output file
NSString *outputPath = [myDocumentsDirectory() stringByAppendingPathComponent:@"m_export.mp3"];
NSURL *outputURL = [NSURL fileURLWithPath:outputPath];
NSLog (@"creating output file %@", outputURL);
AudioFileID outputFile;
CheckResult(AudioFileCreateWithURL((__bridge CFURLRef)outputURL,
kAudioFileCAFType,
&myPCMFormat,
kAudioFileFlags_EraseFile,
&outputFile),
"AudioFileCreateWithURL failed");
// start convertin'
UInt32 outputFilePacketPosition = 0; //in bytes
while (true) {
// wrap the destination buffer in an AudioBufferList
AudioBufferList convertedData;
convertedData.mNumberBuffers = 1;
convertedData.mBuffers[0].mNumberChannels = myPCMFormat.mChannelsPerFrame;
convertedData.mBuffers[0].mDataByteSize = outputBufferSize;
convertedData.mBuffers[0].mData = ioBuf;
UInt32 frameCount = packetsPerBuffer;
// read from the extaudiofile
CheckResult (ExtAudioFileRead(inputFile,
&frameCount,
&convertedData),
"Couldn't read from input file");
if (frameCount == 0) {
printf ("done reading from file");
break;
}
// write the converted data to the output file
CheckResult (AudioFileWritePackets(outputFile,
false,
frameCount,
NULL,
outputFilePacketPosition / myPCMFormat.mBytesPerPacket,
&frameCount,
convertedData.mBuffers[0].mData),
"Couldn't write packets to file");
NSLog (@"Converted %ld bytes", outputFilePacketPosition);
// advance the output file write location
outputFilePacketPosition += (frameCount * myPCMFormat.mBytesPerPacket);
}
// clean up
ExtAudioFileDispose(inputFile);
AudioFileClose(outputFile);
// show size in label
NSLog (@"checking file at %@", outputPath);
[self transMitFile:outputPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputPath]) {
NSError *fileManagerError = nil;
unsigned long long fileSize = [[[NSFileManager defaultManager] attributesOfItemAtPath:outputPath
error:&fileManagerError]
fileSize];
}
any suggestion?.......thanks for your great help!
