ApsaraVideo Live:Time shifting

Enable time shifting

You can enable time shifting for a live stream in the ApsaraVideo Live console or through the API. After you enable the feature, the configuration takes effect only for newly ingested streams.

 
// Replace placeholders 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 of the live content. Unit: days. Valid values: 1 to 30. Default value: 7.
openLiveShiftRequest.setVision("<7>");
// Specify whether to ignore the time-shifting 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 playback

After you enable the time shifting feature for a live stream, ApsaraVideo Live stores the TS segments of the live stream for a specified period. Viewers can send playback requests with time-shifting parameters to access the previously streamed content. 

The playback request is formed by appending the following parameters to the end of the M3U8 URL of a live stream:

• aliyunols=on: This parameter is required if the playback request is sent over Alibaba Cloud CDN.

• Time-shifting parameter: The structure is lhs_{type}_{format}_{unit}_{zone}.

  The following table describes the variables in the time-shifting parameter.

  Variable	Description
  type	The type of time-shifting parameter. Valid values: start: the start time of the playback. end: the end time of the playback in live mode. vodend: the end time of the playback in video-on-demand (VOD) mode. In VOD mode, the server returns a manifest that contains all TS segments in the requested timeframe and an endlist tag. This allows viewers to fast forward and rewind the video as desired.  offset: the amount of time by which the live stream is rewound from the time of request. Important You must specify a start parameter or an offset parameter. If both are specified, the playback prioritizes the offset parameter.  The end and vodend parameters are optional. If neither of them is specified, the end of the manifest grows as the live content progresses. If both are specified, the playback prioritizes the vodend parameter.
  format	The time format. Valid values: unix: Unix timestamp. human: human-readable time in yyyyMMddHHmmss format.
  unit	The unit of time. Valid values: s: seconds. ms: milliseconds.
  zone	The time zone. Valid values: 0 to 9. For example, a value of 8 indicates UTC+8. Set this variable to 0 if the format is unix.

Request example 1

http://<DomainName>/<AppName>/<StreamName.m3u8>?aliyunols=on&lhs_offset_unix_s_0=300&auth_key=3sdda******

In this example, the time-shifting parameter is lhs_offset_unix_s_0=300, which indicates rewinding the live stream by 300 seconds.

Request example 2

http://<DomainName>/<AppName>/<StreamName.m3u8>?aliyunols=on&lhs_start_human_s_8=20171024160220&lhs_end_human_s_8=20171024160420

In this example, the time-shifting parameters are lhs_start_human_s_8=20171024160220 and lhs_end_human_s_8=20171024160420, which indicates playing live content from 16:02:20 to 16:04:20 on October 24, 2017.

Query the timeline of a live stream

If you want to know which periods are accessible for time-shifted viewing, you can send an HTTP Get request to query the timeline of a live stream. 

Sample code

// Replace placeholders with actual values.
http://<DomainName>/openapi/timeline/query?aliyunols=on&app=<AppName>&stream=<StreamName>&format=ts&lhs_start_unix_s_0=<StartTime>&lhs_end_unix_s_0=<endTime>&auth_key=<auth_key>

The following table describes the parameters.

Sample response

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

Time shifting for transcoded streams

To allow viewers to access transcoded streams for time-shifted viewing, enable time shifting for transcoded streams.

Procedure

1. Configure transcoding for the source stream. For more information, see Live stream transcoding.

2. Enable time shifting for the source stream and transcoded streams. Sample code:

// Specify whether to ignore the time-shifting data of transcoded streams. Valid values: true and false. Default value: true.
openLiveShiftRequest.setIgnoreTranscode("<false>"); 

3. Add the time-shifting parameters to the URL of a transcoded stream to rewind the transcoded stream. Sample URL:

http://<DomainName>/<AppName>/<StreamName_transcoding template ID.m3u8>?aliyunols=on&lhs_offset_unix_s_0=300&auth_key=3sdda******

Time shifting for encapsulated streams

You can utilize time shifting with live stream encapsulation.

To rewind an encapsulated stream, add the time-shifting parameters to its URL. Sample URL:

http://<DomainName>/<AppName>/<StreamName-Container format.m3u8>?aliyunols=on&lhs_offset_unix_s_0=300&auth_key=3sdda******

References

• For information about the APIs related to the time shifting feature, see Time shifting.

• To ensure a stable and smooth time-shifted viewing experience, we recommend that you use ApsaraVideo Player. For more information, see ApsaraVideo Live Player SDK.