Azure媒体服务-3gp文件返回错误“；不支持文件类型或编解码器&”；

在Azure Media Services中尝试上传、转换/编码和准备.3gp视频文件时，我们会收到错误File type or codec not supported.。根据此信息，应该支持导入3gp。如何正确导入3gp并将其转换为MP4？

以下是我们的内部日志：

The job stopped due to cancellation or an error.
Job ID: nb:jid:UUID:6dc360df-de54-eb45-ae0d-bdc3d2c810fe
Job Name: Encoding and Packaging for dedf426e0b5b41199e8a111f27744890
Job State: Error
Error Details:  
Task Id: nb:tid:UUID:12424cbb-0013-4685-8e6b-b224d99db186
    Error Code: UserInput
    Error Message: File type or codec not supported.

我们的代码：

/// <summary>
/// This method performs all processing necessary to the media in question. This method will wait while processing is completed.
/// </summary>
/// <param name="fileName">Unique file name with extension</param>
/// <returns>IsSuccess</returns>
public bool ProcessMedia(string fileName)
{
    var mediaCloud = GetCloudMediaContext();
    string assetName = GetAssetNameFromFileName(fileName);
    var asset = mediaCloud.Assets.Where(a => a.Name == assetName).SingleOrDefault();
    IJob job = mediaCloud.Jobs.Create("Encoding and Packaging for " + asset.Name);
    var encoder = GetMediaProcessor(_mediaProcessorNameMap[MediaProcessors.WindowsAzureMediaEncoder]);
    /* Firing off a chain of encoding jobs
     * 1) Original Encoding -> MP4 (Direct download stream)
     * 2) MP4 -> IIS Smooth Streaming (Microsoft Silverlight)
     * 3) IIS -> HLS (Apple and IOS) */
    //MP4
    var mp4Task = job.Tasks.AddNew(String.Format("MP4 Encoding for {0}", asset.Name), encoder, "H264 Broadband 720p", TaskOptions.None);
    mp4Task.InputAssets.Add(asset);
    var mp4Asset = mp4Task.OutputAssets.AddNew(String.Format(MP4_ASSET_NAME_FORMAT, asset.Name), AssetCreationOptions.None);
    //Generate thumbnails from MP4
    foreach (ThumbnailTypes thumbnailType in Enum.GetValues(typeof(ThumbnailTypes)))
    {
        var thumbnailTask = job.Tasks.AddNew(String.Format("Thumbnail Generation for {0}", asset.Name), encoder, 
            String.Format(TASK_THUMBNAIL_GENERATION_FORMAT, thumbnailType, ImageProcessor.ThumbnailSizes[thumbnailType].Height), 
            TaskOptions.None);
        thumbnailTask.InputAssets.Add(mp4Asset);
        var thumnailAsset = thumbnailTask.OutputAssets.AddNew(String.Format(THUMBNAIL_ASSET_NAME_FORMAT, thumbnailType, asset.Name), AssetCreationOptions.None);
    }
    //IIS
    var encodingTask = job.Tasks.AddNew(String.Format("IIS Encoding for {0}", asset.Name), encoder, "H264 Smooth Streaming 720p", TaskOptions.None);
    encodingTask.InputAssets.Add(mp4Asset);
    var ssOutput = encodingTask.OutputAssets.AddNew(String.Format(IIS_ASSET_NAME_FORMAT, asset.Name), AssetCreationOptions.None);
    //HLS
    var packager = GetMediaProcessor(_mediaProcessorNameMap[MediaProcessors.WindowsAzureMediaPackager]);
    var conversionTask = job.Tasks.AddNew(String.Format("HLS Packaging for {0}", asset.Name), packager, TASK_MSMOOTH_TO_HLS, TaskOptions.None);
    conversionTask.InputAssets.Add(ssOutput);
    conversionTask.OutputAssets.AddNew(String.Format(HLS_ASSET_NAME_FORMAT, asset.Name), AssetCreationOptions.None);
    if (job.Tasks.Count() == 0) //no processing was required
        return true;
    job.StateChanged += new EventHandler<JobStateChangedEventArgs>(StateChanged);
    job.Submit();
    // Check job execution and wait for job to finish. 
    Task progressJobTask = job.GetExecutionProgressTask(CancellationToken.None);
    progressJobTask.Wait();
    return job.State == JobState.Finished;
}