基于Node.js使用Azure Media Services转码生成HLS流的技术咨询

背景 #

原AWS架构通过Lambda触发Elastic Transcoder，将S3上传的视频转码为多画质HLS流。现已将S3替换为Azure Blob Storage，需基于Azure Media Services实现相同转码逻辑。

1. Node.js中使用Azure Media Services转码为HLS的示例 #

以下示例基于Azure Media Services v3 SDK（@azure/arm-mediaservices）实现，对应原AWS Lambda的转码逻辑：

前置准备 #

• 安装依赖：npm install @azure/arm-mediaservices @azure/identity @azure/storage-blob dotenv
• 配置环境变量：Azure订阅ID、资源组名、Media Services账户名、Blob存储连接字符串、存储账户名

代码示例 #

const { DefaultAzureCredential } = require("@azure/identity");
const { AzureMediaServices } = require("@azure/arm-mediaservices");
const { BlobServiceClient } = require("@azure/storage-blob");
const dotenv = require("dotenv");

dotenv.config();

// 初始化客户端
const credential = new DefaultAzureCredential();
const mediaServicesClient = new AzureMediaServices(
  credential,
  process.env.AZURE_SUBSCRIPTION_ID
);
const blobServiceClient = BlobServiceClient.fromConnectionString(
  process.env.AZURE_STORAGE_CONNECTION_STRING
);

// 核心转码函数
async function transcodeVideoToHLS(blobName, containerName) {
  const accountName = process.env.AZURE_MEDIA_SERVICES_ACCOUNT_NAME;
  const resourceGroupName = process.env.AZURE_RESOURCE_GROUP_NAME;
  
  // 1. 创建Media Services Asset（关联Blob存储中的源视频）
  const assetName = `input-asset-${Date.now()}`;
  const asset = await mediaServicesClient.assets.createOrUpdate(
    resourceGroupName,
    accountName,
    assetName,
    {
      description: "Input asset for video transcoding",
      storageAccountName: process.env.AZURE_STORAGE_ACCOUNT_NAME
    }
  );

  // 2. 将Blob中的视频复制到Asset对应的存储容器
  const sourceContainerClient = blobServiceClient.getContainerClient(containerName);
  const sourceBlobClient = sourceContainerClient.getBlobClient(blobName);
  const assetContainerClient = blobServiceClient.getContainerClient(asset.container);
  const destinationBlobClient = assetContainerClient.getBlobClient(blobName);
  await destinationBlobClient.syncCopyFromURL(sourceBlobClient.url);

  // 3. 创建或复用Transform（对应AWS Preset，定义转码规则）
  const transformName = "MultiBitrateHLS";
  try {
    await mediaServicesClient.transforms.get(resourceGroupName, accountName, transformName);
  } catch (err) {
    // 创建包含多画质HLS和MP4输出的Transform
    await mediaServicesClient.transforms.createOrUpdate(
      resourceGroupName,
      accountName,
      transformName,
      {
        description: "Multi-bitrate HLS + MP4 transcoding preset",
        outputs: [
          // HLS多码率自适应流（360p/480p/720p/1080p+64k音频）
          {
            preset: {
              "@odata.type": "#Microsoft.Media.StandardEncoderPreset",
              codecs: [
                {
                  "@odata.type": "#Microsoft.Media.H264Video",
                  keyFrameInterval: "PT2S",
                  complexity: "Balanced",
                  layers: [
                    { bitrate: 600000, width: "640", height: "360", label: "360p" },
                    { bitrate: 1500000, width: "854", height: "480", label: "480p" },
                    { bitrate: 3000000, width: "1280", height: "720", label: "720p" },
                    { bitrate: 6000000, width: "1920", height: "1080", label: "1080p" }
                  ]
                },
                {
                  "@odata.type": "#Microsoft.Media.AacAudio",
                  bitrate: 64000,
                  channels: 2
                }
              ],
              formats: [
                {
                  "@odata.type": "#Microsoft.Media.HlsFormat",
                  filenamePattern: "{Basename}_{Label}_{Bitrate}",
                  segmentsPerTsFile: 10 // 对应原SegmentDuration=10
                }
              ]
            }
          },
          // 额外MP4输出（对应原AWS的MP4 Preset）
          {
            preset: {
              "@odata.type": "#Microsoft.Media.StandardEncoderPreset",
              codecs: [
                {
                  "@odata.type": "#Microsoft.Media.H264Video",
                  keyFrameInterval: "PT2S",
                  complexity: "Balanced",
                  layers: [{ bitrate: 5000000, width: "1920", height: "1080" }]
                },
                {
                  "@odata.type": "#Microsoft.Media.AacAudio",
                  bitrate: 128000,
                  channels: 2
                }
              ],
              formats: [
                {
                  "@odata.type": "#Microsoft.Media.Mp4Format",
                  filenamePattern: "{Basename}_1080p.mp4"
                }
              ]
            }
          }
        ]
      }
    );
  }

  // 4. 创建转码Job
  const jobName = `transcode-job-${Date.now()}`;
  const outputAssetName = `output-asset-${Date.now()}`;
  await mediaServicesClient.jobs.create(
    resourceGroupName,
    accountName,
    transformName,
    jobName,
    {
      input: {
        "@odata.type": "#Microsoft.Media.JobInputAsset",
        assetName: assetName
      },
      outputs: [
        {
          "@odata.type": "#Microsoft.Media.JobOutputAsset",
          assetName: outputAssetName
        }
      ]
    }
  );

  console.log(`转码任务已启动：${jobName}`);
  console.log(`输出文件将存储在Asset：${outputAssetName}`);
}

// Azure Function触发器入口（监听Blob上传事件）
module.exports = async function (context, myBlob) {
  const blobName = context.bindingData.name;
  const containerName = context.bindingData.containerName;
  
  try {
    await transcodeVideoToHLS(blobName, containerName);
    context.done(null, "转码任务初始化成功");
  } catch (err) {
    context.log.error(err);
    context.done(err);
  }
};

2. 视频存储：Blob Storage还是Media Services Assets？ #

• 核心结论：转码操作必须基于Media Services Assets，但源视频可先存储在Blob Storage，再关联到Assets；转码后的输出默认存储在Assets对应的Blob容器中，也可复制到其他Blob容器用于分发。
• 详细说明：
  • Assets是Media Services的核心载体：Media Services的转码、流式处理等功能仅支持Assets作为输入输出，Assets本质是Blob Storage容器的逻辑封装，由Media Services管理权限和生命周期。
  • Blob Storage可作为源存储：用户上传的视频可直接存在Blob Storage中，无需迁移，只需将文件复制或关联到Media Services Asset即可触发转码。
  • 输出文件的处理：转码后的HLS流和MP4文件会自动保存到Output Asset对应的Blob容器，可直接通过Media Services流式终结点分发，也可复制到公共Blob容器配合CDN加速分发。

内容的提问来源于stack exchange，提问作者Ammar Abdul Aziz