GPAC’s contributions to MPEG 105th meeting

The 105th MPEG meeting was held in Vienna, Austria. The GPAC team presented many contributions (see below) to the Systems group related to the ISO Base Media File Format, the MPEG-2 Transport Stream or the MPEG-DASH standards. The contributions were largely well received. This post gives some details.

ISO Base Media File Format

  • We submitted a contribution to improve the efficiency of the file format regarding sample grouping, with a mechanism to signal default grouping of samples. The group agreed to include a slightly modified proposal into the Amendment 3 of the standard.
  • Another contribution was proposed to indicate track dependencies, for example between SVC, MVC, SHVC… tracks more efficiently than using extractors. The group decided to produce a Technology under Consideration document to document the use cases and proposed solution, and to welcome further feedback.
  • We also proposed a mechanism to describe HEVC tiles in the MP4 file format. The group agreed to use our document as a basis for amendment to the ISO Base Media File Format and to integrate modifications proposed by Ericsson and Sony.
  • We provided feedback from the implementation of the carriage of WebVTT in MP4 in GPAC. See more technical details on this here. This resulted in a formal resolution from MPEG: “The systems group thanks the GPAC team for their implementation and verification work related to ISO/IEC 14496-30 and for providing both valuable feedback about the specification and open-source implementation.”


  • We made also a proposal regarding low latency in DASH. The group discussed this proposal with other proposals from Sharp and Qualcomm and decided to add it as part of a Technology under Consideration document for a future amendment to MPEG-DASH.
  • In DASH, we proposed to add a ‘codec’ parameter to the MIME type to enable advanced signaling of the codecs used by a DASH presentation. The group prefered to rely only the ‘profiles’ parameter and to defer to the DASH IF to keep a catalogue of what profiles require what codecs.
  • We also had a contribution informing about the new features of GPAC related to MPEG-DASH, including DashCast and MSE (more details here).
  • Finally, we presented some ideas to improve DASH for eMBMS scenarios.


  • We presented a contribution in JCT-VC regarding HEVC, reporting a System/Video integration issue, regarding picture boundaries detection and independent slices processing order. The problem reported was acknowledged but due to deployment constraints it was not accepted as a corrigendum item in the HEVC standard but will be dealt with at the Systems level.


  • We presented a follow-up on hybrid MPEG-2 TS/broadband delivery scenarios with an updated proposed working draft and a contribution related to the carriage of packed SVC/MVC frames within a single PES in MPEG-2 TS.