Constraints on Dolby AC-4 elementary streams within MPEG-DASH ISO base media file format segments

A Dolby AC-4 elementary stream must meet certain conditions to be delivered via MPEG-DASH.

Annex E of ETSI TS 103 190-2 describes the constraints that must be applied to the Dolby AC-4 bitstream for storage within the ISO base media file format. Additionally, for MPEG-DASH applications that use the ISO base media file format, these constraints apply:

  • The value of the bitstream_version parameter must be 2.

  • The value of the frame_rate_index parameter must remain constant.

  • The value of the presentation_config parameter must remain constant.

  • The value of the fs_index parameter must remain constant.

  • The value of the channel_mode parameter must remain constant.

  • The value of the content_classifier parameter must remain constant.

  • The Dolby AC-4 random access points must be encoded correctly to ensure compliance with the requirements described in Packetizing the Dolby AC-4 bitstream.

  • We strongly recommend that Dolby AC-4 elementary streams be encoded with the same frame rate as the associated video frame rate to ensure constant alignment of video and audio access units in order to utilize the features of A/V alignment.

If a Dolby AC-4 elementary stream does not meet the requirements stated in this specification, the multiplexer may halt processing and inform the user that the bitstream is not compliant.