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Audio Selector in Services

Specify which audio track or PID is used for transcription in a service using the Audio Selection feature.

The Audio Selection are now part of  Step 2 - Input Media - SRT or HLS in the Create Service Wizard.

NOTE: Audio Selection is only available for SRT and HLS PULL

SRT

To access the Audio Selection, navigate to Step 2: Input Media - SRT when creating or editing a Service, and click the Audio Selection dropdown on the page. Use Audio Selection when your input stream contains multiple audio tracks (e.g., different languages, commentary feeds, or isolated audio sources) and you need to specify which track and channels to use for transcription. 

Please see Step 2: Input Media (SRT) - How do I use SRT as an Input source for my Service using the new UI? for more information

Audio Selector Enabled: Toggle this option ON to enable audio track and channel selection. When disabled, the Service will automatically use the default audio from your input stream.

Audio Track: Enter the audio track you want to use for transcription. This is useful when your input stream contains multiple audio tracks (such as different languages or audio feeds).

TIP: The audio index starts from 1. The track order is determined by the Program Map Table (PMT) in your MPEG transport stream. PIDs should be specified like `PID 255`, `#255`, `PID 0xFF`, or `0xFF`. Default is the first audio track.

Audio Channels: Select which audio channels within the selected audio track should be used for processing. You can choose from:

  • Not Set - Use the default channel configuration.
  • Included - Opens a channel selector where you can specify one or more channels to include. Click Add Item to add additional channel selections, and use the text field to specify channel indices (starting from 0). Use the delete (trash) icon to remove channel selections. Leave empty to select all channels in the track.

HLS

To access the Audio Selection, navigate to Step 2: Input Media - HLS PULL when creating or editing a Service, and click the Audio Selection dropdown on the page. Use Audio Selection when your input stream contains multiple audio tracks (e.g., different languages, commentary feeds, or isolated audio sources) and you need to specify which track and channels to use for transcription.

Please see Step 2: Input Media (HLS) - How do I use HLS as an Input source for my Service using the new UI? for more information

Audio Selector Enabled: Toggle this option ON to enable audio variant selection. When disabled, the Service will automatically use the default audio from your input stream.



Audio Group Id: Enter the audio variant group ID from your HLS manifest. This field identifies the group of audio variants available in your stream. The Group ID corresponds to the GROUP-ID attribute in the HLS manifest's EXT-X-MEDIA tag.

Audio Variant Name: Enter the audio variant name that should be used for transcription. This field identifies the specific audio variant within the group. The variant name corresponds to the NAME attribute in the HLS manifest's EXT-X-MEDIA tag.

NOTE: These values must match the audio group and variant identifiers in your HLS manifest. Check your HLS manifest file to find the correct Group ID and Variant Name values for your desired audio track. To view your HLS manifest, open the .m3u8 URL in a text editor or browser. Look for lines beginning with #EXT-X-MEDIA to find your audio variants.

NOTES:

  • The Audio Selection option only works when you choose HLS PULL as the Input Stream Type

  • HLS PUSH automatically uses the default audio from your stream