When an AudioFormatReader is created via the AudioFormatManager using an InputStream, there is only one way to check which format it is, by trying to create a reader. In ogg & flac this can be done switftly by checking the “magic” doubleword at the beginning like:
public:
//==============================================================================
FlacReader (InputStream* const in)
: AudioFormatReader (in, formatName),
reservoir (2, 0),
reservoirStart (0),
samplesInReservoir (0),
scanningForLength (false),
ok (false),
decoder (0)
{
int64 oldPos = input->getPosition();
int32 flacMagic = input->readIntBigEndian();
bool seekOk = input->setPosition(oldPos);
if (flacMagic == 'fLaC' && seekOk)
{
lengthInSamples = 0;
decoder = FLAC__stream_decoder_new();and for the ogg reader:
public:
//==============================================================================
OggReader (InputStream* const inp)
: AudioFormatReader (inp, formatName),
reservoir (2, 2048),
reservoirStart (0),
samplesInReservoir (0)
{
memset( &ovFile, 0, sizeof(OggVorbis_File) );
int64 oldPos = input->getPosition();
int32 oggMagic = input->readIntBigEndian();
bool seekOk = input->setPosition(0);
if (oggMagic == 'OggS' && seekOk)
{
sampleRate = 0;
usesFloatingPointData = true;
callbacks.read_func = &oggReadCallback;
callbacks.seek_func = &oggSeekCallback;
callbacks.close_func = &oggCloseCallback;
callbacks.tell_func = &oggTellCallback;
const int err = ov_open_callbacks (input, &ovFile, 0, 0, callbacks);
if (err == 0)
{
vorbis_info* info = ov_info (&ovFile, -1);
lengthInSamples = (uint32) ov_pcm_total (&ovFile, -1);
numChannels = info->channels;
bitsPerSample = 16;
sampleRate = info->rate;
reservoir.setSize (numChannels,
(int) jmin (lengthInSamples, (int64) reservoir.getNumSamples()));
}
}
}
~OggReader()
{
if (ovFile.datasource != 0)
{
ov_clear (&ovFile);
}
}