AC4SpecificBox and Dolby AC-4 bitstream parameter conflicts

The AC4SpecificBox is intended to be used by the system for information purposes only.

For example, the system might use the AC4SpecificBox for any of these scenarios:

  • Informing the onscreen display of the channel configuration of the audio stream
  • Offering the user the ability to select between the different audio services that are being carried (in the case where multiple independent substreams are present)
  • Recovering errors (if there is an interruption in audio data delivery and the system cannot ascertain the configuration of the complete Dolby AC-4 bitstream from the substream structure in the MP4 sample due to CRC errors)

Because it is possible that differences may occur between the AC4SpecificBox and the parameters of the Dolby AC-4 bitstream, the information from the AC4SpecificBox must not be used to configure the audio decoder or the audio subsystem of the device. If the device encounters a conflict, the Dolby AC-4 bitstream parameter value must always take precedence over the value of the corresponding parameter in the AC4SpecificBox.