如何调用ffmpeg.exe来转换Windows Azure上的音频文件？

Question

我在Windows Azure上运行Web角色以接收AAC音频文件(由base64字符串上传)并将它们存储到blob中.它现在工作正常.

接下来,我还必须将它们转换为MP3并将MP3存储到blob中.我决定使用像ffmpeg.exe -i path .aac path .mp3这样的东西.

问题是:

1. 如何在Web角色的Web服务中调用外部ffmpeg.exe？
2. 会是什么路？

如果你知道,请帮助我.先感谢您.

Answer 1

我建议你为webrole 使用本地存储资源,在那里你可以从blob存储下载AAC文件,并将它们转换为MP3.然后上传回blob存储.

另请注意,您还可以使用Path.GetTempFileName()来获取AAC/MP3文件的临时文件名,但我不鼓励这样做(即使我之前已经这样做过).

至于运行的执行ffmpeg,您可能想要浏览我之前构建的AzureVideoConv的代码.你会在那里找到很多有用的代码.

以下是实际ffmpeg调用的示例(请注意,我从blob存储中下载exe,以避免使用外部exe文件膨胀我的azure包,并在需要时轻松更新ffmpeg.exe):

        internal void ConvertFile(string inputFileName, Guid taskID)
    {
        string tmpName = string.Format(
            "{0}\\{1}.flv",
            Path.GetTempPath(), inputFileName.Substring(inputFileName.LastIndexOf("\\")+1));
        ProcessStartInfo psi = new ProcessStartInfo();
        psi.FileName = this._processorExecutable;
        psi.Arguments = string.Format(@"-i ""{0}"" -y ""{1}""", inputFileName, tmpName);
        psi.CreateNoWindow = true;
        psi.ErrorDialog = false;
        psi.UseShellExecute = false;
        psi.WindowStyle = ProcessWindowStyle.Hidden;
        psi.RedirectStandardOutput = true;
        psi.RedirectStandardInput = false;
        psi.RedirectStandardError = true;
        try
        {
            // Start the process with the info we specified.
            // Call WaitForExit and then the using statement will close.
            using (Process exeProcess = Process.Start(psi))
            {
                exeProcess.PriorityClass = ProcessPriorityClass.High;
                string outString = string.Empty;
                // use ansynchronous reading for at least one of the streams
                // to avoid deadlock
                exeProcess.OutputDataReceived += (s, e) => {
                    outString += e.Data;
                };
                exeProcess.BeginOutputReadLine();
                // now read the StandardError stream to the end
                // this will cause our main thread to wait for the
                // stream to close (which is when ffmpeg quits)
                string errString = exeProcess.StandardError.ReadToEnd();
                Trace.WriteLine(outString);
                Trace.TraceError(errString);
                byte[] fileBytes = File.ReadAllBytes(tmpName);
                if (fileBytes.Length > 0)
                {
                    this._sSystem.SaveOutputFile(
                        fileBytes, 
                        tmpName.Substring(tmpName.LastIndexOf("\\")+1),
                        taskID
                        );
                }
            }
        }
        catch (Exception e)
        {
            Trace.TraceError(e.Message);
        }
    }

注意项目的最后一次检入是使用Windows Azure SDK 1.3

Answer 2

非常感谢@astaykov.你做得好.虽然它不是特定于我的情况(我需要一段特定的代码而不是整个大型项目),但它确实激励了我.为了说明我的情况,我将自己回答这个问题 - 请注意,我是根据@ astaykov的代码在某处直接复制和粘贴的.

1. 首先,使用本地存储资源配置角色.然后通过这些代码得到它的路径:

       LocalResource converter_path = 
              RoleEnvironment.GetLocalResource("AudioConvertSpace");
       string rootPathName = converter_path.RootPath;
   

2. 在本地存储中获取ffmpeg.exe,xxx.aac和xxx.mp3的路径:

       string aac_path = rootPathName + "\\" + "fmwa-" + guidguid + ".aac";
       string mp3_path = rootPathName + "\\" + "fmwa-" + guidguid + ".mp3";
       string exe_path = rootPathName + "\\" + "ffmpeg.exe";
   

3. 将.aac文件写入本地存储:

       System.IO.File.WriteAllBytes(aac_path, decoded_audio_byte_array);
   

4. 请记住,本地存储不能保证稳定或持久,因此请检查ffmpeg.exe是否存在 - 如果不存在,请从blob下载.

       if (System.IO.File.Exists(exe_path) == false)
       {
           var exeblob = _BlobContainer.GetBlobReference("ffmpeg.exe");
           exeblob.DownloadToFile(exe_path, null);
       }
   

5. 初始化并运行ffmpeg.exe进程:

       ProcessStartInfo psi = new ProcessStartInfo();
       psi.FileName = exe_path;
       psi.Arguments = string.Format(@"-i ""{0}"" -y ""{1}""", 
                                          aac_path, mp3_path);
       psi.CreateNoWindow = true;
       psi.ErrorDialog = false;
       psi.UseShellExecute = false;
       psi.WindowStyle = ProcessWindowStyle.Hidden;
       psi.RedirectStandardOutput = true;
       psi.RedirectStandardInput = false;
       psi.RedirectStandardError = true;
       Process exeProcess = Process.Start(psi);
       exeProcess.PriorityClass = ProcessPriorityClass.High;
       string outString = string.Empty;
       exeProcess.OutputDataReceived += (s, e) => {
                   outString += e.Data;
               };
       exeProcess.BeginOutputReadLine();
       string errString = exeProcess.StandardError.ReadToEnd();
       Trace.WriteLine(outString);
       Trace.TraceError(errString);
       exeProcess.WaitForExit();
   

6. 将ffmpeg.exe的输出上传到blob存储中:

       byte[] mp3_audio_byte_array = System.IO.File.ReadAllBytes(mp3_path);
       var mp3blob = _BlobContainer.GetBlobReference("fmwa-"+guidguid+".mp3");
       mp3blob.Properties.ContentType = "audio/mp3";
       mp3blob.UploadByteArray(mp3_audio_byte_array);
   

7. 清理临时文件:

       System.IO.File.Delete(aac_path);
       System.IO.File.Delete(mp3_path);