ApsaraVideo Live:Time shifting

How time shifting works

Time shifting is based on the HTTP Live Streaming (HLS) protocol. HLS breaks down a live stream into TS segments and generates an M3U8 index file to record the order of the TS segments in real time. When you request the live stream, the index file that contains the URLs of the TS segments is returned. Generally, TS segments and the corresponding URLs are not stored. Therefore, you cannot rewind a live stream to view previously streamed content. To resolve this issue, you can enable time shifting to store TS segments in an Object Storage Service (OSS) bucket and the corresponding URLs in a dataset for up to 30 days. For information about how to specify the retention period, see Configure time shifting.

Usage notes

The feature allows up to 100,000 viewers to watch a live stream at the same time. If you want to raise the upper limit, submit a ticket. For more information, see Contact us.

Enable time shifting

To enable time shifting, use one of the following methods:

Method 1: Enable time shifting in the ApsaraVideo Live console. For more information, see Configure time shifting.

Method 2: Call the OpenLiveShift operation.

The following sample code provides an example on how to call the API operation by using the server SDK for Java:

 
// Replace the placeholder values with actual values.
DefaultProfile profile = DefaultProfile.getProfile("<regionId>", "<ALIBABA_CLOUD_ACCESS_KEY_ID>", "<ALIBABA_CLOUD_ACCESS_KEY_SECRET>");
IAcsClient client = new DefaultAcsClient(profile);
OpenLiveShiftRequest openLiveShiftRequest = new OpenLiveShiftRequest();
openLiveShiftRequest.setDomainName("<DomainName>");
openLiveShiftRequest.setAppName("<AppName>");
openLiveShiftRequest.setStreamName("<StreamName>");
// The retention period. Unit: day. Valid values: 1 to 30. Default value: 7.
openLiveShiftRequest.setVision("<5>");
// Specifies whether to ignore the time-shifted data of transcoded streams. Valid values: true and false. Default value: true.
openLiveShiftRequest.setIgnoreTranscode("<true>");
//
// Code for other features.
//

try {
    OpenLiveShiftResponse openLiveShiftResponse = client.getAcsResponse(openLiveShiftRequest);
    System.out.println(new Gson().toJson(openLiveShiftResponse));
    // todo something.
} catch (ServerException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (ClientException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

Send a request for time-shifted viewing

To construct a request for time-shifted viewing, add the required parameters to the HLS URL of a live stream. The required parameters are in the following format: lhs_{type}_{format}_{unit}_{zone}. Sample request:

http://example.com/AppName/StreamName.m3u8?aliyunols=on&lhs_start_human_s_8=20171024160220&lhs_end_human_s_8=20171024160420

The following table describes the required parameters.

Examples:

• lhs_start_human_s_8=20170809200010

• lhs_start_unix_s_0=1502280113

• lhs_end_human_s_8=20170809200010

• lhs_vodend_unix_s_0=1502280113

• lhs_offset_unix_ms_0=1800000: specifies to rewind the live stream by 30 minutes.

Query the valid time range for time-shifted viewing

You can send a request to query the valid time range for time-shifted viewing. The request is constructed by adding the required parameters to a request URL in the following format: http://{domain}/openapi/timeline/query. Examples:

// An unsigned URL
http://example.com/openapi/timeline/query?aliyunols=on&app=bbb&stream=cc&format=ts&lhs_end_unix_s_0=1513334270&lhs_start_unix_s_0=1513334255

// A signed URL
http://example.com/openapi/timeline/query?auth_key=1606204918-0-0-3e898a5f491fedb113d17aad7c091dde&aliyunols=on&app=zzb-test&stream=zzb-shiyi&format=ts&lhs_start_unix_s_0=1606200900&lhs_end_unix_s_0=1606202520

Sample response:

{
  "retCode": 0,
  "description": "success",
  "content": {
    "current": 1514269063,
    "timeline": [
      {
        "start": 1514269054,
        "end": 1514269058
      },
      {
        "start": 1514269058,
        "end": 1514269062
      }
    ]
  }
}