Question

我正在使用Windows Azure Media Services .NET SDK 3来使用流媒体服务。我想检索视频的持续时间。如何使用Windows Azure Media Services .NET SDK 3检索视频的持续时间？

Answer 1

Azure会创建一些元数据文件（xml），可以在此期间查询这些文件。可以使用媒体服务扩展

访问这些文件

https://github.com/Azure/azure-sdk-for-media-services-extensions

获取资产元数据：

// The asset encoded with the Windows Media Services Encoder. Get a reference to it from the context.
IAsset asset = null;

// Get a SAS locator for the asset (make sure to create one first).
ILocator sasLocator = asset.Locators.Where(l => l.Type == LocatorType.Sas).First();

// Get one of the asset files.
IAssetFile assetFile = asset.AssetFiles.ToList().Where(af => af.Name.EndsWith(".mp4", StringComparison.OrdinalIgnoreCase)).First();

// Get the metadata for the asset file.
AssetFileMetadata manifestAssetFile = assetFile.GetMetadata(sasLocator);

TimeSpan videoDuration = manifestAssetFile.Duration;

Answer 2

在Azure Media Services SDK中，我们仅通过contentFileSize（https://msdn.microsoft.com/en-us/library/azure/hh974275.aspx）提供资产的大小。但是，我们不提供视频元数据（例如持续时间）。当您获得流媒体定位器时，该播放将告诉您视频资产的持续时间。

干杯，严明飞

Answer 3

如果您使用的是AMSv3，则AdaptiveStreaming作业将在输出资产中生成一个video_manifest.json文件。您可以对其进行解析以获取持续时间。这是一个示例：

public async Task<TimeSpan> GetVideoDurationAsync(string encodedAssetName)
{
    var encodedAsset = await ams.Assets.GetAsync(config.ResourceGroup, config.AccountName, encodedAssetName);
    if(encodedAsset is null) throw new ArgumentException("An asset with that name doesn't exist.", nameof(encodedAssetName));
    var sas = GetSasForAssetFile("video_manifest.json", encodedAsset, DateTime.Now.AddMinutes(2));
    var responseMessage = await http.GetAsync(sas);
    var manifest = JsonConvert.DeserializeObject<Amsv3Manifest>(await responseMessage.Content.ReadAsStringAsync());
    var duration = manifest.AssetFile.First().Duration;
    return XmlConvert.ToTimeSpan(duration);
}

对于Amsv3Manifest模型和示例video_manifest.json文件，请参阅：https://app.quicktype.io/?share=pAhTMFSa3HVzInAET5k4

您可以使用GetSasForAssetFile()的以下定义开始学习：

private string GetSasForAssetFile(string filename, Asset asset, DateTime expiry)
{
    var client = GetCloudBlobClient();
    var container = client.GetContainerReference(asset.Container);
    var blob = container.GetBlobReference(filename);

    var offset = TimeSpan.FromMinutes(10);
    var policy = new SharedAccessBlobPolicy
    {
        SharedAccessStartTime = DateTime.UtcNow.Subtract(offset),
        SharedAccessExpiryTime = expiry.Add(offset),
        Permissions = SharedAccessBlobPermissions.Read
    };
    var sas = blob.GetSharedAccessSignature(policy);
    return $"{blob.Uri.AbsoluteUri}{sas}";
}

private CloudBlobClient GetCloudBlobClient()
{
    if(CloudStorageAccount.TryParse(storageConfig.ConnectionString, out var storageAccount) is false)
    {
        throw new ArgumentException(message: "The storage configuration has an invalid connection string.", paramName: nameof(config));
    }

    return storageAccount.CreateCloudBlobClient();
}

如何从Azure媒体服务获取视频的持续时间？

3 个答案: