public AudioInfo ReadAudioInfo(Stream stream)
{
Contract.Ensures(Contract.Result <AudioInfo>() != null);
var mp4 = new Mp4(stream);
uint dataSize = mp4.GetChildAtomInfo().Single(atom => atom.FourCC == "mdat").Size;
mp4.DescendToAtom("moov", "trak", "mdia", "minf", "stbl", "stts");
var stts = new SttsAtom(mp4.ReadAtom(mp4.CurrentAtom));
uint sampleCount = stts.PacketCount * stts.PacketSize;
mp4.DescendToAtom("moov", "trak", "mdia", "minf", "stbl", "stsd", "mp4a", "esds");
var esds = new EsdsAtom(mp4.ReadAtom(mp4.CurrentAtom));
if (esds.SampleRate > 0)
{
return(new AudioInfo(string.Format(CultureInfo.CurrentCulture, "{0}kbps MPEG 4 AAC",
esds.AverageBitrate > 0
? (int)esds.AverageBitrate / 1000
: CalculateBitRate(dataSize, sampleCount, esds.SampleRate)), esds.Channels, 0,
(int)esds.SampleRate, sampleCount));
}
// Apple Lossless files have their own atom for storing audio info:
mp4.DescendToAtom("moov", "trak", "mdia", "minf", "stbl", "stsd", "alac");
var alac = new AlacAtom(mp4.ReadAtom(mp4.CurrentAtom));
return(new AudioInfo("Apple Lossless", alac.Channels, alac.BitsPerSample, (int)alac.SampleRate,
sampleCount));
}
public MetadataDictionary ReadMetadata(Stream stream)
{
var mp4 = new Mp4(stream);
mp4.DescendToAtom("moov", "udta", "meta", "ilst");
return(new AtomToMetadataAdapter(mp4, mp4.GetChildAtomInfo()));
}
public void WriteMetadata(Stream stream, MetadataDictionary metadata, SettingsDictionary settings)
{
var originalMp4 = new Mp4(stream);
AtomInfo[] topAtoms = originalMp4.GetChildAtomInfo();
// Create a temporary stream to hold the new atom structure:
using (var tempStream = new MemoryStream())
{
var tempMp4 = new Mp4(tempStream);
// Copy the ftyp and moov atoms to the temporary stream:
originalMp4.CopyAtom(topAtoms.Single(atom => atom.FourCC == "ftyp"), tempStream);
originalMp4.CopyAtom(topAtoms.Single(atom => atom.FourCC == "moov"), tempStream);
// Move to the start of the list atom:
originalMp4.DescendToAtom("moov", "udta", "meta", "ilst");
tempMp4.DescendToAtom("moov", "udta", "meta", "ilst");
// Remove any copied ilst atoms, then generate new ones:
tempStream.SetLength(tempStream.Position);
byte[] ilstData = GenerateIlst(originalMp4, metadata, settings);
tempStream.Write(ilstData, 0, ilstData.Length);
// Update the ilst and parent atom sizes:
tempMp4.UpdateAtomSizes((uint)tempStream.Length - tempMp4.CurrentAtom.End);
// Update the creation times if they're being set explicitly:
DateTime creationTime;
if (!string.IsNullOrEmpty(settings["CreationTime"]))
{
if (DateTime.TryParse(settings["CreationTime"], out creationTime))
{
UpdateCreationTimes(creationTime, tempMp4);
}
else
{
throw new InvalidSettingException(string.Format(CultureInfo.CurrentCulture,
Resources.MetadataEncoderBadCreationTime, settings["CreationTime"]));
}
}
// Update the stco atom to reflect the new location of mdat:
var mdatOffset = (int)(tempStream.Length - topAtoms.Single(atom => atom.FourCC == "mdat").Start);
tempMp4.UpdateStco(mdatOffset);
// Copy the mdat atom to the temporary stream, after the moov atom:
tempStream.Seek(0, SeekOrigin.End);
originalMp4.CopyAtom(topAtoms.Single(atom => atom.FourCC == "mdat"), tempStream);
// Overwrite the original stream with the new, optimized one:
stream.SetLength(tempStream.Length);
stream.Position = 0;
tempStream.Position = 0;
tempStream.CopyTo(stream);
}
}
static byte[] GenerateIlst(Mp4 originalMp4, MetadataDictionary metadata, SettingsDictionary settings)
{
Contract.Requires(originalMp4 != null);
Contract.Requires(metadata != null);
Contract.Requires(settings != null);
Contract.Ensures(Contract.Result <byte[]>() != null);
using (var resultStream = new MemoryStream())
{
var adaptedMetadata = new MetadataToAtomAdapter(metadata, settings);
// "Reverse DNS" atoms may need to be preserved:
foreach (ReverseDnsAtom reverseDnsAtom in
from listAtom in originalMp4.GetChildAtomInfo()
where listAtom.FourCC == "----"
select new ReverseDnsAtom(originalMp4.ReadAtom(listAtom)))
{
switch (reverseDnsAtom.Name)
{
// Always preserve the iTunSMPB (gapless playback) atom:
case "iTunSMPB":
resultStream.Write(reverseDnsAtom.GetBytes(), 0, reverseDnsAtom.GetBytes().Length);
break;
// Preserve the existing iTunNORM atom if a new one isn't provided, and AddSoundCheck isn't explicitly False:
case "iTunNORM":
if (!adaptedMetadata.IncludesSoundCheck &&
string.Compare(settings["AddSoundCheck"], bool.FalseString,
StringComparison.OrdinalIgnoreCase) != 0)
{
resultStream.Write(reverseDnsAtom.GetBytes(), 0, reverseDnsAtom.GetBytes().Length);
}
break;
}
}
byte[] atomData = adaptedMetadata.GetBytes();
resultStream.Write(atomData, 0, atomData.Length);
return(resultStream.ToArray());
}
}