WP7 Mp3MediaStreamSource 演示不起作用 [英] WP7 Mp3MediaStreamSource demo not working

问题描述

我在 http://archive.msdn.microsoft.com/ManagedMediaHelpers 上下载了 Mp3MediaStreamSource 演示但可以让它与我的流一起工作，你能帮帮我吗?

I dowloaded Mp3MediaStreamSource demo on http://archive.msdn.microsoft.com/ManagedMediaHelpers but can get it worked with my stream, can you help me?

我的流:

private static string mediaFileLocation = "http://server2.fmstreams.com:8011/spin103";

如果 1 没有调用 RequestCallback:

In case 1 is RequestCallback not called:

request.AllowReadStreamBuffering = true; 
IAsyncResult result = request.BeginGetResponse(new AsyncCallback(this.RequestCallback), null);

如果 2 调用了 RequestCallback 但我收到错误:当缓冲被禁用时，主线程不支持读取.

In case 2 is RequestCallback called but I'm getting error: Read is not supported on the main thread when buffering is disabled.

request.AllowReadStreamBuffering = false;
IAsyncResult result = request.BeginGetResponse(new AsyncCallback(this.RequestCallback), null);

推荐答案

您需要在不同的线程中阅读标题.

You need to read the header in a different thread.

public class Mp3MediaStreamSource : MediaStreamSource
{
    /// <summary>
    ///  ID3 version 1 tags are 128 bytes at the end of the file.
    ///  http://www.id3.org/ID3v1
    /// </summary>
    private const int Id3Version1TagSize = 128;

    /// <summary>
    /// Buffer for decoding audio frames into.  4096 should be larger than we'll ever need, right? (144*448*1000/44100)
    /// </summary>
    private static byte[] buffer = new byte[4096];

    /// <summary>
    /// The Mp3 stream being played back.
    /// </summary>
    private Stream audioStream;

    /// <summary>
    /// Description of the Mp3 Stream being played back which includes the
    /// MpegLayer3WaveFormat structure serialized out as a string of hex 
    /// characters.
    /// </summary>
    private MediaStreamDescription audioStreamDescription;

    /// <summary>
    /// The position in the stream where the current MpegFrame starts.
    /// For purposes of this code, the frame starts with the header and
    /// not after the header.
    /// </summary>
    private long currentFrameStartPosition;

    /// <summary>
    /// The length of the audiostream as determined via the constructors.
    /// </summary>
    private long audioStreamLength;

    /// <summary>
    /// Holds the duration of the track
    /// </summary>
    private TimeSpan trackDuration;

    /// <summary>
    /// The current frame to parse
    /// </summary>
    private MpegFrame currentFrame;

    private MpegFrame mpegLayer3Frame;

    private bool readHeaderFail = false;

    /// <summary>
    /// Initializes a new instance of the Mp3MediaStreamSource class with a pre-determined length.
    /// This is useful for wrapping an IO stream that may not be seekable (and thus won't have a .Length)
    /// but for which you already know the length (e.g. a CryptoStream from an IsolatedStorageFileStream with a byte count,
    /// or an HTTP stream which has a specified content-length)
    /// </summary>
    /// <param name="audioStream">Non-seekable Stream containing Mp3 data</param>
    /// <param name="length">Length of non-seekable stream</param>
    public Mp3MediaStreamSource(Stream audioStream, long length)
    {
        this.audioStream = audioStream;
        this.audioStreamLength = length;
    }

    /// <summary>
    /// Gets the MpegLayer3WaveFormat structure which represents this Mp3 file.
    /// </summary>
    public MpegLayer3WaveFormat MpegLayer3WaveFormat { get; private set; }

    /// <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. Should
    /// probably do something a bit more robust at some point.
    /// </summary>
    /// <returns>
    /// The first MpegFrame in the audio stream.
    /// </returns>
    public MpegFrame ReadPastId3V2Tags()
    {
        /* 
         * 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;

            // 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);
        }
        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);
        }

        return mpegFrame;

        // 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");
    }

    /// <summary>
    /// Parses the passed in MediaStream to find the first frame and signals
    /// to its parent MediaElement that it is ready to begin playback by calling
    /// ReportOpenMediaCompleted.
    /// </summary>
    protected override void OpenMediaAsync()
    {
        // Initialize data structures to pass to the Media pipeline via the MediaStreamSource
        Dictionary<MediaSourceAttributesKeys, string> mediaSourceAttributes = new Dictionary<MediaSourceAttributesKeys, string>();
        Dictionary<MediaStreamAttributeKeys, string> mediaStreamAttributes = new Dictionary<MediaStreamAttributeKeys, string>();
        List<MediaStreamDescription> mediaStreamDescriptions = new List<MediaStreamDescription>();

        ThreadStart ts = new ThreadStart(ReadHeader);
        Thread t = new Thread(ts);
        t.Start();

        do
        {
            System.Threading.Thread.Sleep(10);
        }
        while (mpegLayer3Frame == null && !readHeaderFail);

        if (mpegLayer3Frame == null)
            throw new InvalidOperationException("Header is unreadable");

        // Mp3 frame validity check.
        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();
        this.MpegLayer3WaveFormat.WaveFormatExtensible = wfx;

        this.MpegLayer3WaveFormat.WaveFormatExtensible.FormatTag = 85;
        this.MpegLayer3WaveFormat.WaveFormatExtensible.Channels = (short)((mpegLayer3Frame.Channels == Channel.SingleChannel) ? 1 : 2);
        this.MpegLayer3WaveFormat.WaveFormatExtensible.SamplesPerSec = mpegLayer3Frame.SamplingRate;
        this.MpegLayer3WaveFormat.WaveFormatExtensible.AverageBytesPerSecond = mpegLayer3Frame.Bitrate / 8;
        this.MpegLayer3WaveFormat.WaveFormatExtensible.BlockAlign = 1;
        this.MpegLayer3WaveFormat.WaveFormatExtensible.BitsPerSample = 0;
        this.MpegLayer3WaveFormat.WaveFormatExtensible.ExtraDataSize = 12;

        this.MpegLayer3WaveFormat.Id = 1;
        this.MpegLayer3WaveFormat.BitratePaddingMode = 0;
        this.MpegLayer3WaveFormat.FramesPerBlock = 1;
        this.MpegLayer3WaveFormat.BlockSize = (short)mpegLayer3Frame.FrameSize;
        this.MpegLayer3WaveFormat.CodecDelay = 0;

        mediaStreamAttributes[MediaStreamAttributeKeys.CodecPrivateData] = this.MpegLayer3WaveFormat.ToHexString();
        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.ReportOpenMediaCompleted(mediaSourceAttributes, mediaStreamDescriptions);

        this.currentFrame = mpegLayer3Frame;
        this.currentFrameStartPosition = MpegFrame.FrameHeaderSize;
    }

    private void ReadHeader()
    {
        try
        {
            mpegLayer3Frame = this.ReadPastId3V2Tags();
        }
        catch
        {
            readHeaderFail = true;
        }
    }

    /// <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)
    {
        try
        {
            Dictionary<MediaSampleAttributeKeys, string> emptyDict = new Dictionary<MediaSampleAttributeKeys, string>();
            MediaStreamSample audioSample = null;

            if (this.currentFrame != null)
            {
                // Calculate our current position
                double ratio = (double)this.currentFrameStartPosition / (double)this.audioStreamLength;
                TimeSpan currentPosition = new TimeSpan((long)(this.trackDuration.Ticks * ratio));

                // 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.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.ReportGetSampleCompleted(audioSample);
            }
        }
        catch (Exception ex)
        {

        }
    }

    /// <summary>
    ///  TODO FILL ME IN LATER
    /// </summary>
    protected override void CloseMedia()
    {
        try
        {
            this.audioStream.Close();
        }
        catch (CryptographicException)
        {
            // Ignore these, they are thrown when abruptly closing a
            // stream (i.e. skipping tracks) where the source is a
            // CryptoStream
        }
        catch (Exception e)
        {
            Debug.Assert(false, e.StackTrace);
        }
    }

    /// <summary>
    ///  TODO FILL ME IN LATER
    /// </summary>
    /// <param name="diagnosticKind">
    ///  TODO FILL ME IN LATER . . .
    /// </param>
    protected override void GetDiagnosticAsync(MediaStreamSourceDiagnosticKind diagnosticKind)
    {
        throw new NotImplementedException();
    }

    /// <summary>
    /// <para>
    /// Effectively a Null-Op for when a MediaElement requests a seek at the beginning
    /// of the stream. This makes the stream semi-unseekable.
    /// </para>
    /// <para>
    /// In a fuller MediaStreamSource, the logic here would be to actually seek to
    /// the correct mpeg frame matching the seekToTime passed in.
    /// </para>
    /// </summary>
    /// <param name="seekToTime">
    ///  The time to seek to in nanosecond ticks.
    /// </param>
    protected override void SeekAsync(long seekToTime)
    {
        this.ReportSeekCompleted(seekToTime);
    }

    /// <summary>
    ///  TODO FILL ME IN LATER
    /// </summary>
    /// <param name="mediaStreamDescription">
    ///  TODO FILL ME IN LATER . . .
    /// </param>
    protected override void SwitchMediaStreamAsync(MediaStreamDescription mediaStreamDescription)
    {
        throw new NotImplementedException();
    }
}

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