/// <summary> /// Reads the next mp3 frame /// </summary> /// <returns>Next mp3 frame, or null if EOF</returns> private Mp3Frame ReadNextFrame(bool readData) { Mp3Frame frame = null; try { frame = Mp3Frame.LoadFromStream(mp3Stream, readData); if (frame != null) { tocIndex++; } } catch (EndOfStreamException) { // suppress for now - it means we unexpectedly got to the end of the stream // half way through } return(frame); }
/// <summary> /// Opens MP3 from a stream rather than a file /// Will not dispose of this stream itself /// </summary> /// <param name="inputStream">The incoming stream containing MP3 data</param> /// <param name="frameDecompressorBuilder">Factory method to build a frame decompressor</param> public Mp3FileReader(Stream inputStream, FrameDecompressorBuilder frameDecompressorBuilder) { if (inputStream == null) { throw new ArgumentNullException("inputStream"); } try { mp3Stream = inputStream; id3v2Tag = Id3v2Tag.ReadTag(mp3Stream); dataStartPosition = mp3Stream.Position; var firstFrame = Mp3Frame.LoadFromStream(mp3Stream); if (firstFrame == null) { throw new InvalidDataException("Invalid MP3 file - no MP3 Frames Detected"); } double bitRate = firstFrame.BitRate; xingHeader = XingHeader.LoadXingHeader(firstFrame); // If the header exists, we can skip over it when decoding the rest of the file if (xingHeader != null) { dataStartPosition = mp3Stream.Position; } // workaround for a longstanding issue with some files failing to load // because they report a spurious sample rate change var secondFrame = Mp3Frame.LoadFromStream(mp3Stream); if (secondFrame != null && (secondFrame.SampleRate != firstFrame.SampleRate || secondFrame.ChannelMode != firstFrame.ChannelMode)) { // assume that the first frame was some kind of VBR/LAME header that we failed to recognise properly dataStartPosition = secondFrame.FileOffset; // forget about the first frame, the second one is the first one we really care about firstFrame = secondFrame; } this.mp3DataLength = mp3Stream.Length - dataStartPosition; // try for an ID3v1 tag as well mp3Stream.Position = mp3Stream.Length - 128; byte[] tag = new byte[128]; mp3Stream.Read(tag, 0, 128); if (tag[0] == 'T' && tag[1] == 'A' && tag[2] == 'G') { id3v1Tag = tag; this.mp3DataLength -= 128; } mp3Stream.Position = dataStartPosition; // create a temporary MP3 format before we know the real bitrate this.Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate, firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate); CreateTableOfContents(); this.tocIndex = 0; // [Bit rate in Kilobits/sec] = [Length in kbits] / [time in seconds] // = [Length in bits ] / [time in milliseconds] // Note: in audio, 1 kilobit = 1000 bits. // Calculated as a double to minimize rounding errors bitRate = (mp3DataLength * 8.0 / TotalSeconds()); mp3Stream.Position = dataStartPosition; // now we know the real bitrate we can create an accurate MP3 WaveFormat this.Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate, firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate); decompressor = frameDecompressorBuilder(Mp3WaveFormat); this.waveFormat = decompressor.OutputFormat; this.bytesPerSample = (decompressor.OutputFormat.BitsPerSample) / 8 * decompressor.OutputFormat.Channels; // no MP3 frames have more than 1152 samples in them // some MP3s I seem to get double this.decompressBuffer = new byte[1152 * bytesPerSample * 2]; } catch (Exception) { if (ownInputStream) { inputStream.Dispose(); } throw; } }