c# - 将通过 HTTP 流式传输的 wav 实时转换为 mp3

Question

背景:我正在使用一项返回 MIME 类型为 audio/wav 的数据的服务.我需要为此音频提供播放机制(目前构建为 MVC 应用程序)。例如，我的端点看起来像 https://audio.fooservice.com/GetAudio?audioId=123

音频为 8kHz，1 channel u-law。

由于在使用 HTML5 时跨浏览器支持的格式不同 <audio>标签，我无法使用原始的 u-law wav，因为 Internet Explorer 不会播放它。

我建议的解决方案是从源格式实时转换为 mp3。

我已经从这里和 NAudio 论坛中的各种其他问题中拼凑出一个部分可行的解决方案，但它引发了一个异常，如下面的评论所述:

private void NAudioTest(string url)
{
    Stream outStream = new MemoryStream();
    var format = WaveFormat.CreateMuLawFormat(8000, 1);

    using (Stream ms = new MemoryStream())
    {
        var request = (HttpWebRequest)WebRequest.Create(url);
        request.KeepAlive = false;
        request.ProtocolVersion = HttpVersion.Version10;

        using (Stream stream = request.GetResponse().GetResponseStream())
        {
            using (var reader = new RawSourceWaveStream(stream, format))
            {
                // reader is not seekable; we need to convert to a byte array to seek
                var bytes = reader.ToByteArray();

                // create a new stream from the byte aray
                var seekableStream = new MemoryStream(bytes);

                // instantiating a WaveFileReader as follows will throw an exception:
                // "System.FormatException: Not a WAVE file - no RIFF header"
                using (var waveReader = new WaveFileReader(seekableStream))
                {
                    using (var pcmStream = WaveFormatConversionStream.CreatePcmStream(waveReader))
                    {
                        var pcmBytes = pcmStream.ToByteArray();
                        var mp3 = pcmBytes.ToMp3();
                    }
                }
            }
        }
    }
}

public static class StreamExtensions
{
    public static byte[] ToByteArray(this Stream stream)
    {
        var ms = new MemoryStream();
        var buffer = new byte[1024];
        int bytes = 0;

        while ((bytes = stream.Read(buffer, 0, buffer.Length)) > 0)
            ms.Write(buffer, 0, bytes);

        return ms.ToArray();
    }
}

public static class ByteExtensions
{
    public static byte[] ToMp3(this byte[] bytes)
    {
        using (var outStream = new MemoryStream())
        {
            using (var ms = new MemoryStream(bytes))
            {
                using (var reader = new WaveFileReader(ms))
                {
                    using (var writer = new LameMP3FileWriter(outStream, reader.WaveFormat, 64))
                    {
                        reader.CopyTo(writer);
                        return outStream.ToArray();
                    }
                }
            }
        }
    }
}

一天中的大部分时间我都在研究这个问题，我觉得我正在将不必要的复杂性引入到一些看起来应该相当简单的事情中。

如有任何帮助，我们将不胜感激。

注意:我无法更改源格式，并且需要支持 IE。

编辑:我解决了 RIFF 异常并且能够生成 MP3 流，但它只是白噪声。希望我也能解决这个问题。我的新代码如下:

[HttpGet]
public ActionResult GetMp3(string url)
{
    if (String.IsNullOrWhiteSpace(url))
        return null;

    var muLawFormat = WaveFormat.CreateMuLawFormat(8000, 1);
    var compressedStream = new MemoryStream();

    using (var ms = new MemoryStream())
    {
        var request = (HttpWebRequest)WebRequest.Create(url);
        request.KeepAlive = false;
        request.ProtocolVersion = HttpVersion.Version10;

        using (Stream webStream = request.GetResponse().GetResponseStream())
        {
            var buffer = new byte[4096];
            int read;
            while (webStream != null && (read = webStream.Read(buffer, 0, buffer.Length)) > 0)
                ms.Write(buffer, 0, read);
        }

        ms.Position = 0;

        using (WaveStream wav = WaveFormatConversionStream.CreatePcmStream(new RawSourceWaveStream(ms, muLawFormat)))
        using (var mp3 = new LameMP3FileWriter(compressedStream, new WaveFormat(), LAMEPreset.MEDIUM_FAST))
            wav.CopyTo(mp3);
    }

    compressedStream.Seek(0, 0);
    return new FileStreamResult(compressedStream, "audio/mpeg");
}

Answer 1

这对我有用(我需要做你想做的事)。希望这对其他人也有帮助。我将 NAudio 与 LAME 一起使用。

您必须确保将 libmp3lamexx.dll 文件复制到网络服务器的 BIN 位置或 %PATH% 变量中的某个文件夹，否则它将无法工作。

        string sq = /* URL of WAV file (http://foo.com/blah.wav) */

        Response.ContentType = "audio/mpeg";

        using (WebClient wc = new WebClient())
        {
            if (!sq.ToLower().EndsWith(".wav"))
            {
                byte[] rawFile = wc.DownloadData(sq.Trim());
                Response.OutputStream.Write(rawFile, 0, rawFile.Length);
            }
            else
            {
                using (var wavReader = new WaveFileReader(new MemoryStream(wc.DownloadData(sq.Trim()))))
                {
                    try
                    {
                        using (var wavWriter = new LameMP3FileWriter(Response.OutputStream, wavReader.WaveFormat, LAMEPreset.ABR_128))
                        {
                            wavReader.CopyTo(wavWriter);
                        }
                    }
                    catch (ArgumentException)
                    {
                        var newFormat = new WaveFormat(wavReader.WaveFormat.SampleRate, 16, 2);

                        using (var pcmStream = new WaveFormatConversionStream(newFormat, wavReader))
                        {
                            using (var wavWriter = new LameMP3FileWriter(Response.OutputStream, pcmStream.WaveFormat, LAMEPreset.ABR_128))
                            {
                                pcmStream.CopyTo(wavWriter);
                            }
                        }
                    }
                }
            }

            Response.Flush();
            Response.End();
        }