/// <summary>
/// Parses the next sample from the requested stream and then calls ReportGetSampleCompleted
/// to inform its parent MediaElement of the next sample.
/// </summary>
/// <param name="mediaStreamType">
/// Should always be Audio for this MediaStreamSource.
/// </param>
protected override void GetSampleAsync(MediaStreamType mediaStreamType)
{
Dictionary<MediaSampleAttributeKeys, string> emptyDict = new Dictionary<MediaSampleAttributeKeys, string>();
MediaStreamSample audioSample = null;
this.Log("Yay! Sample requested!");
if (this.currentFrame != null)
{
// Calculate our current position based on the stream's length
//// double ratio = (double)this.currentFrameStartPosition / (double)this.audioStreamLength;
//// TimeSpan currentPosition = new TimeSpan((long)(this.trackDuration.Ticks * ratio));
// Calculate our current position instead based on the bitrate of the stream (more accurate?)
double position = (double)this.currentFrameStartPosition / (double)this.currentFrame.Bitrate;
TimeSpan currentPosition = TimeSpan.FromSeconds(position * 8 /* bits per Byte */);
// Create a MemoryStream to hold the bytes
// FrameSize includes the frame header which we've already read from the previous iteration, so just copy the
// header, and then read the remaining bytes
this.currentFrame.CopyHeader(buffer);
int audioSampleSize = this.currentFrame.FrameSize - MpegFrame.FrameHeaderSize;
int c = this.audioStream.Read(buffer, MpegFrame.FrameHeaderSize, audioSampleSize);
if (c != audioSampleSize)
{
// Ran out of bytes trying to read MP3 frame.
this.currentFrame = null;
audioSample = new MediaStreamSample(this.audioStreamDescription, null, 0, 0, 0, emptyDict);
this.ReportGetSampleCompleted(audioSample);
return;
}
this.currentFrameStartPosition += c;
using (MemoryStream audioFrameStream = new MemoryStream(buffer))
{
// Return the next sample in the stream
audioSample = new MediaStreamSample(this.audioStreamDescription, audioFrameStream, 0, this.currentFrame.FrameSize, currentPosition.Ticks, emptyDict);
this.ReportGetSampleCompleted(audioSample);
// Grab the next frame
MpegFrame nextFrame = new MpegFrame(this.audioStream);
if ((nextFrame.Version == 1 || nextFrame.Version == 2) && nextFrame.Layer == 3)
{
this.currentFrameStartPosition += MpegFrame.FrameHeaderSize;
this.currentFrame = nextFrame;
}
else
{
this.currentFrame = null;
}
}
}
else
{
// We're near the end of the file, or we got an irrecoverable error.
// Return a null stream which tells the MediaStreamSource & MediaElement to shut down
audioSample = new MediaStreamSample(this.audioStreamDescription, null, 0, 0, 0, emptyDict);
this.Log("Reporting GetSampleCompleted called");
this.ReportGetSampleCompleted(audioSample);
}
}
/// <summary>
/// Callback which handles setting up an MSS once the first MpegFrame after Id3v2 data has been read.
/// </summary>
/// <param name="mpegLayer3Frame"> First MpegFrame</param>
/// <param name="mediaStreamAttributes">Empty dictionary for MediaStreamAttributes</param>
/// <param name="mediaStreamDescriptions">Empty dictionary for MediaStreamDescriptions</param>
/// <param name="mediaSourceAttributes">Empty dictionary for MediaSourceAttributes</param>
private void ReadPastId3v2TagsCallback(
MpegFrame mpegLayer3Frame,
Dictionary<MediaStreamAttributeKeys, string> mediaStreamAttributes,
List<MediaStreamDescription> mediaStreamDescriptions,
Dictionary<MediaSourceAttributesKeys, string> mediaSourceAttributes)
{
if (mpegLayer3Frame.FrameSize <= 0)
{
throw new InvalidOperationException("MpegFrame's FrameSize cannot be negative");
}
// Initialize the Mp3 data structures used by the Media pipeline with state from the first frame.
WaveFormatExtensible wfx = new WaveFormatExtensible();
this.MpegLayer3WaveFormat = new MpegLayer3WaveFormat();
wfx.FormatTag = 0x55;//mp3
wfx.Channels = (short)((mpegLayer3Frame.Channels == Channel.SingleChannel) ? 1 : 2);
wfx.SamplesPerSec = mpegLayer3Frame.SamplingRate;
wfx.AverageBytesPerSecond = mpegLayer3Frame.Bitrate / 8;
wfx.BlockAlign = 1;
wfx.BitsPerSample = 0;
wfx.ExtraDataSize = 12;
this.MpegLayer3WaveFormat.WaveFormatExtensible = wfx;
this.MpegLayer3WaveFormat.Id = 1;
this.MpegLayer3WaveFormat.BitratePaddingMode = 0;
this.MpegLayer3WaveFormat.FramesPerBlock = 1;
this.MpegLayer3WaveFormat.BlockSize = (short)mpegLayer3Frame.FrameSize;
this.MpegLayer3WaveFormat.CodecDelay = 0;
var hexCodecData = MpegLayer3WaveFormat.ToHexString();
mediaStreamAttributes[MediaStreamAttributeKeys.CodecPrivateData] = hexCodecData;
this.audioStreamDescription = new MediaStreamDescription(MediaStreamType.Audio, mediaStreamAttributes);
mediaStreamDescriptions.Add(this.audioStreamDescription);
this.trackDuration = new TimeSpan(0, 0, (int)(this.audioStreamLength / MpegLayer3WaveFormat.WaveFormatExtensible.AverageBytesPerSecond));
mediaSourceAttributes[MediaSourceAttributesKeys.Duration] = this.trackDuration.Ticks.ToString(CultureInfo.InvariantCulture);
if (this.audioStream.CanSeek)
{
mediaSourceAttributes[MediaSourceAttributesKeys.CanSeek] = "1";
}
else
{
mediaSourceAttributes[MediaSourceAttributesKeys.CanSeek] = "0";
}
// Report that the Mp3MediaStreamSource has finished initializing its internal state and can now
// pass in Mp3 Samples.
this.Log("Reporting open Media completed");
this.ReportOpenMediaCompleted(mediaSourceAttributes, mediaStreamDescriptions);
this.currentFrame = mpegLayer3Frame;
this.currentFrameStartPosition = MpegFrame.FrameHeaderSize;
}
/// <summary>
/// Read off the Id3Data from the stream and return the first MpegFrame of the audio stream.
/// This assumes that the first bit of data is either an ID3 segment or an MPEG segment. Calls a separate thread
/// to read past ID3v2 data.
/// </summary>
/// <param name="callback">
/// Callback that can process the first MpegFrame and set up the MSS. Called back once the thread has skipped
/// over all of the Id3V2 tags.
/// </param>
public void ReadPastId3V2Tags(Action<MpegFrame> callback)
{
/*
* Since this code assumes that the first bit of data is either an ID3 segment or an MPEG segment it could
* get into trouble. Should probably do something a bit more robust at some point.
*/
MpegFrame mpegFrame;
// Read and (throw out) any Id3 data if present.
byte[] data = new byte[10];
if (this.audioStream.Read(data, 0, 3) != 3)
{
goto cleanup;
}
if (data[0] == 73 /* I */ &&
data[1] == 68 /* D */ &&
data[2] == 51 /* 3 */)
{
// Need to update to read the is footer present flag and account for its 10 bytes if needed.
if (this.audioStream.Read(data, 3, 7) != 7)
{
goto cleanup;
}
int id3Size = BitTools.ConvertSyncSafeToInt32(data, 6);
int bytesRead = 0;
//TODO:SS: try remove this Task.Run (we probably dont need threads in BG agent)
// Read through the ID3 Data tossing it out.)
while (id3Size > 0)
{
bytesRead = (id3Size - buffer.Length > 0)
? this.audioStream.Read(buffer, 0, buffer.Length)
: this.audioStream.Read(buffer, 0, id3Size);
id3Size -= bytesRead;
}
mpegFrame = new MpegFrame(this.audioStream);
callback(mpegFrame);
}
else
{
// No ID3 tag present, presumably this is streaming and we are starting right at the Mp3 data.
// Assume the stream isn't seekable.
if (this.audioStream.Read(data, 3, 1) != 1)
{
goto cleanup;
}
mpegFrame = new MpegFrame(this.audioStream, data);
callback(mpegFrame);
}
return;
// Cleanup and quit if you couldn't even read the initial data for some reason.
cleanup:
throw new Exception("Could not read intial audio stream data");
}
