private static void ParsePicture(Stream fs, ref FlacInfo info)
{
var pictureType = fs.BEInt32();
var mimeStringLength = (int)fs.BEInt32();
var mimeType = Encoding.ASCII.GetString(fs.ReadBytes(mimeStringLength), 0, mimeStringLength);
var descriptionLength = (int)fs.BEInt32();
var description = Encoding.UTF8.GetString(fs.ReadBytes(descriptionLength), 0, descriptionLength);
var pictureWidth = fs.BEInt32();
var pictureHeight = fs.BEInt32();
var colorDepth = fs.BEInt32();
var indexedColorCount = fs.BEInt32();
var pictureDataLength = fs.BEInt32();
fs.Seek(pictureDataLength, SeekOrigin.Current);
info.HasCover = true;
if (pictureType > 20)
{
pictureType = 21;
}
Logger.Log($" | picture type: {PictureTypeName[pictureType]}");
Logger.Log($" | picture format type: {mimeType}");
if (descriptionLength > 0)
{
Logger.Log($" | description: {description}");
}
Logger.Log($" | attribute: {pictureWidth}px*{pictureHeight}px@{colorDepth}-bit");
if (indexedColorCount != 0)
{
Logger.Log($" | indexed-color color: {indexedColorCount}");
}
}
private static void ParseStreamInfo(Stream fs, ref FlacInfo info)
{
var minBlockSize = fs.BEInt16();
var maxBlockSize = fs.BEInt16();
var minFrameSize = fs.BEInt24();
var maxFrameSize = fs.BEInt24();
var buffer = fs.ReadBytes(8);
var br = new BitReader(buffer);
var sampleRate = br.GetBits(20);
var channelCount = br.GetBits(3) + 1;
var bitPerSample = br.GetBits(5) + 1;
var totalSample = br.GetBits(36);
var md5 = fs.ReadBytes(16);
info.RawLength = channelCount * bitPerSample / 8 * totalSample;
info.SampleRate = sampleRate;
info.BitPerSample = bitPerSample;
Logger.Log($" | minimum block size: {minBlockSize}, maximum block size: {maxBlockSize}");
Logger.Log($" | minimum frame size: {minFrameSize}, maximum frame size: {maxFrameSize}");
Logger.Log($" | Sample rate: {sampleRate}Hz, bits per sample: {bitPerSample}-bit");
Logger.Log($" | Channel count: {channelCount}");
var md5String = md5.Aggregate("", (current, item) => current + $"{item:X2}");
Logger.Log($" | MD5: {md5String}");
}
private static void ParseVorbisComment(Stream fs, ref FlacInfo info)
{
//only here in flac use little-endian
var vendorLength = (int)fs.LEInt32();
var vendorRawStringData = fs.ReadBytes(vendorLength);
var vendor = Encoding.UTF8.GetString(vendorRawStringData, 0, vendorLength);
info.Encoder = vendor;
Logger.Log($" | Vendor: {vendor}");
var userCommentListLength = fs.LEInt32();
for (var i = 0; i < userCommentListLength; ++i)
{
var commentLength = (int)fs.LEInt32();
var commentRawStringData = fs.ReadBytes(commentLength);
var comment = Encoding.UTF8.GetString(commentRawStringData, 0, commentLength);
var splitterIndex = comment.IndexOf('=');
var key = comment.Substring(0, splitterIndex);
var value = comment.Substring(splitterIndex + 1, comment.Length - 1 - splitterIndex);
info.VorbisComment[key] = value;
var summary = value.Length > 25 ? value.Substring(0, 25) + "..." : value;
Logger.Log($" | [{key}] = '{summary.Replace('\n', ' ')}'");
}
}
public static FlacInfo GetMetadataFromFlac(string flacPath)
{
Logger.Log(flacPath);
using (var fs = File.OpenRead(flacPath))
{
var info = new FlacInfo();
var id3Header = Encoding.ASCII.GetString(fs.ReadBytes(3), 0, 3);
fs.Seek(0, SeekOrigin.Begin);
if (id3Header == "ID3")
{
SkipID3Block(fs);
Logger.Log(Logger.Level.Warning, $"{flacPath} 文件在头部包含ID3v2标签！");
}
var flacBeginPosition = fs.Position;
var header = Encoding.ASCII.GetString(fs.ReadBytes(4), 0, 4);
if (header != "fLaC")
{
throw new InvalidDataException($"Except an flac but get an {header}" +
$"{Environment.NewLine}File name: {Path.GetFileName(flacPath)}");
}
//METADATA_BLOCK_HEADER
//1-bit Last-metadata-block flag
//7-bit BLOCK_TYPE
//24-bit Length
long metaLength = 4 /*header*/;
while (fs.Position < fs.Length)
{
var blockHeader = fs.BEInt32();
var lastMetadataBlock = blockHeader >> 31 == 0x1;
var blockType = (BlockType)((blockHeader >> 24) & 0x7f);
var length = blockHeader & 0xffffff;
var prePos = fs.Position;
metaLength += length + 4 /*length of METADATA_BLOCK_HEADER*/;
Logger.Log($"|+{blockType} with Length: {length}");
switch (blockType)
{
case BlockType.STREAMINFO:
Debug.Assert(length == 34);
ParseStreamInfo(fs, ref info);
break;
case BlockType.VORBIS_COMMENT:
ParseVorbisComment(fs, ref info);
break;
case BlockType.PICTURE:
ParsePicture(fs, ref info);
break;
case BlockType.PADDING:
case BlockType.APPLICATION:
case BlockType.SEEKTABLE:
case BlockType.CUESHEET:
fs.Seek(length, SeekOrigin.Current);
break;
default:
throw new ArgumentOutOfRangeException($"Invalid BLOCK_TYPE: 0x{blockType:X}");
}
Debug.Assert(fs.Position - prePos == length);
if (lastMetadataBlock)
{
break;
}
}
Debug.Assert(fs.Position == metaLength + flacBeginPosition);
info.TrueLength = fs.Length - fs.Position;
return(info);
}
}
