// --- ======== static builder ========= ---
/// <summary>
/// Parses the input arrays as a DecoderSpecificInfo, as used in MP4 containers.
/// </summary>
/// <param name="data"></param>
/// <returns>a DecoderConfig</returns>
public static DecoderConfig parseMP4DecoderSpecificInfo(byte[] data)
{
var inStream = new BitStream(data);
var config = new DecoderConfig();
try
{
config.profile = readProfile(inStream);
int sf = inStream.readBits(4);
config.sampleFrequency = sf == 0xf ? SampleFrequency.forFrequency(inStream.readBits(24)) : SampleFrequency.forInt(sf);
config.channelConfiguration = (ChannelConfiguration)inStream.readBits(4);
switch (config.profile.type)
{
case Profile.ProfileType.AAC_SBR:
{
config.extProfile = config.profile;
config.sbrPresent = true;
sf = inStream.readBits(4);
// TODO: 24 bits already read; read again?
//if(sf==0xF) config.sampleFrequency = SampleFrequency.forFrequency(inStream.readBits(24));
// if sample frequencies are the same: downsample SBR
config.downSampledSBR = config.sampleFrequency.getIndex() == sf;
config.sampleFrequency = SampleFrequency.forInt(sf);
config.profile = readProfile(inStream);
} break;
case Profile.ProfileType.AAC_MAIN:
case Profile.ProfileType.AAC_LC:
case Profile.ProfileType.AAC_SSR:
case Profile.ProfileType.AAC_LTP:
case Profile.ProfileType.ER_AAC_LC:
case Profile.ProfileType.ER_AAC_LTP:
case Profile.ProfileType.ER_AAC_LD:
{
// ga-specific info:
config.frameLengthFlag = inStream.readBool();
if (config.frameLengthFlag)
{
throw new AACException("config uses 960-sample frames, not yet supported"); //TODO: are 960-frames working yet?
}
config.dependsOnCoreCoder = inStream.readBool();
config.coreCoderDelay = config.dependsOnCoreCoder ? inStream.readBits(14) : 0;
config.extensionFlag = inStream.readBool();
if (config.extensionFlag)
{
if (config.profile.isErrorResilientProfile())
{
config.sectionDataResilience = inStream.readBool();
config.scalefactorResilience = inStream.readBool();
config.spectralDataResilience = inStream.readBool();
}
// extensionFlag3
inStream.skipBit();
}
if (config.channelConfiguration == ChannelConfiguration.CHANNEL_CONFIG_NONE || !config.channelConfiguration.ToString().StartsWith("CHANNEL_", StringComparison.Ordinal))
{
// TODO: is this working correct? -> ISO 14496-3 part 1: 1.A.4.3
inStream.skipBits(3); //PCE
throw new NotImplementedException();
//PCE pce = new PCE();
//pce.decode(inStream);
//config.profile = pce.getProfile();
//config.sampleFrequency = pce.getSampleFrequency();
//config.channelConfiguration = ChannelConfiguration.forInt(pce.getChannelCount());
}
if (inStream.getBitsLeft() > 10)
{
readSyncExtension(inStream, config);
}
} break;
default: throw new AACException("profile not supported: " + config.profile.type);
}
return(config);
}
finally
{
inStream.destroy();
}
}
