/*
Init()
- initialize the decoder with the given configuration
*/
int32_t
alac_decoder_init (ALAC_DECODER *p, void * inMagicCookie, uint32_t inMagicCookieSize)
{
int32_t status = ALAC_noErr;
ALACSpecificConfig theConfig;
uint8_t * theActualCookie = (uint8_t *)inMagicCookie;
uint32_t theCookieBytesRemaining = inMagicCookieSize;
// For historical reasons the decoder needs to be resilient to magic cookies vended by older encoders.
// As specified in the ALACMagicCookieDescription.txt document, there may be additional data encapsulating
// the ALACSpecificConfig. This would consist of format ('frma') and 'alac' atoms which precede the
// ALACSpecificConfig.
// See ALACMagicCookieDescription.txt for additional documentation concerning the 'magic cookie'
// skip format ('frma') atom if present
if (theActualCookie[4] == 'f' && theActualCookie[5] == 'r' && theActualCookie[6] == 'm' && theActualCookie[7] == 'a')
{
theActualCookie += 12;
theCookieBytesRemaining -= 12;
}
// skip 'alac' atom header if present
if (theActualCookie[4] == 'a' && theActualCookie[5] == 'l' && theActualCookie[6] == 'a' && theActualCookie[7] == 'c')
{
theActualCookie += 12;
theCookieBytesRemaining -= 12;
}
// read the ALACSpecificConfig
if (theCookieBytesRemaining >= sizeof(ALACSpecificConfig))
{
theConfig.frameLength = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->frameLength);
if (theConfig.frameLength > ALAC_FRAME_LENGTH)
return fALAC_FrameLengthError ;
theConfig.compatibleVersion = ((ALACSpecificConfig *)theActualCookie)->compatibleVersion;
theConfig.bitDepth = ((ALACSpecificConfig *)theActualCookie)->bitDepth;
theConfig.pb = ((ALACSpecificConfig *)theActualCookie)->pb;
theConfig.mb = ((ALACSpecificConfig *)theActualCookie)->mb;
theConfig.kb = ((ALACSpecificConfig *)theActualCookie)->kb;
theConfig.numChannels = ((ALACSpecificConfig *)theActualCookie)->numChannels;
theConfig.maxRun = Swap16BtoN(((ALACSpecificConfig *)theActualCookie)->maxRun);
theConfig.maxFrameBytes = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->maxFrameBytes);
theConfig.avgBitRate = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->avgBitRate);
theConfig.sampleRate = Swap32BtoN(((ALACSpecificConfig *)theActualCookie)->sampleRate);
p->mConfig = theConfig;
RequireAction( p->mConfig.compatibleVersion <= kALACVersion, return kALAC_ParamError; );
extern "C" int apple_alac_decode_frame(unsigned char *sampleBuffer, uint32_t bufferLength,
unsigned char *dest, int *outsize) {
uint32_t numFrames = 0;
BitBuffer theInputBuffer;
BitBufferInit(&theInputBuffer, sampleBuffer, bufferLength);
theDecoder->Decode(&theInputBuffer, dest, Swap32BtoN(cookie.config.frameLength),
cookie.config.numChannels, &numFrames);
*outsize = numFrames;
return 0;
}
