Extracted Audio-Only Stream (__a__)

When enabled in a Streaming configuration, the Edge server automatically generates an audio-only stream from one of your bit rate streams. You can use the __a__ query string to disable this feature on a per-stream basis. Possible values are on and off. For example:
uri/master.m3u8?__a__=off

This query string is only effective if you are using Media Services Live extracted audio-only stream. If Bit Rate Filtering and the Extracted Audio-Only features are simultaneously enabled, bit rate filtering is applied first, then audio-only extraction is applied to the remaining bit rates.