INTERNATIONAL ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND AUDIO

ISO/IEC JTC1/SC29/WG11 N1375
MPEG 96/
October 1996

Definition of a VM

A verification model (VM) is a completely defined encoding and decoding environment, composed of tools and algorithms, such that an experiment performed by multiple independent parties will produce essentially identical results. A VM specifies input and output formats for the uncoded data, and the format of the bitstream containing the coded data. It specifies an algorithm for encoding and decoding, including functionality, and elements of computational precision. A VM evolves through versions, during the core experiment process.

Construction of a VM

Construction of a VM shall be approved by consensus. A VM shall:

• be built on a cluster of functionalities, including as many functionalities as is practically feasible.
• be as broad (i.e. generic) as possible.
• fit into the MSDL paradigm.
• address a unique set of functionalities, and/or should use a unique technology.
• be built from a library of tools and algorithms.
• include tools and algorithms, based on the following evaluation criteria:
  1. subjective test results, when available
  2. efficacy in addressing the MPEG-4 new, improved, or standard functionalities
  3. added value, for example addressing functionalities not referred to in the Requirements Document
  4. adaptability to relevant changing conditions, such as different input (audio/video content), different (number of) objects, different and/or variable bit rates, different and/or changing error patterns, different temporal and spatial resolutions, or other kinds of adaptability
  5. margins for improvement
  6. complexity

After evaluation of the tool and algorithm proposals, VMs will be built. The number required is determined by the technical content and performance of the proposals received. If it cannot be determined which of two or more tools achieves the desired functionalities best, and the proposals cannot be implemented with a single VM, separate, VMs are needed for each proposal.

The Core Experiment Process

New tools brought to MPEG-4 will be evaluated using the core experiment process. A core experiment is proposed by one or more MPEG experts, and it is approved by consensus, provided that two or more independent experts carry out the experiment. Core experiments verify the inclusion of a new technique or set of techniques. At the heart of the core experiment process are multiple, independent, directly comparable experiments, performed to determine whether or not proposed algorithmic techniques have merits. A core experiment must be completely and uniquely defined, so that the results are unambiguous. In addition to the specification of the algorithmic technique(s) to be evaluated, a core experiment also specifies the parameters to be used (for example, audio sample rate or video resolution), so that the results can be compared.

Source code VM benefits collaboration and can reduce the time and effort associated with VM development. It can also reduce duplication of efforts and promote acceptance of the standard in the market place. Therefore, in addition to the traditional textual description of the VM, MPEG may decide that a source code description of the VM, decoder or both encoder and decoder, be developed and maintained.

In this case a participant in the core experiment process may choose to submit contributions in textual form and, optionally, in source code form. The acceptability of the submission shall be based on its technical merits and not on the form of the submission.

The following applies to the development and maintenance of a source code VM:

1. The architectures of the Audio-Video-Systems software VM are agreed and fully described in WG11 document and updated when necessary;
2. All modules and their interfaces are fully described in a WG11 document or the source code itself and updated when necessary. The source code VM shall be a WG11 document;
3. Modifications to current VM architectures and modules may have to be made to improve efficiency and readability. Such modifications are open to any member and not just the originators of the current programs;
4. All MPEG members are free to use any of the VM modules for the purposes of executing core experiments. One or more experimenters may decide to submit results of a technology used in a core experiment, without providing either textual or source code description. This is accepted for inclusion in the VM when it is judged to be beneficial and the corresponding source code is released and independently verified no later than the beginning of the following meeting. Until the moment the technology is accepted or needs to be verified the originator is allowed to withhold from MPEG disclosure of his/her source code. A textual description shall accompany the source code;
5. VM modules shall be written in well-documented machine-independent C or C++ for Audio, Video, MSDL and SNHC and Java for MSDL and APIs (no assembly or object code may be part of MPEG VM reference programs);
6. The copyright of decoder source code modules representing normative elements is released to ISO/IEC. Any patent needed to implement the VM in either hardware or software still applies;
7. ISO/IEC gives users of the standard free licence to use the normative elements of the VM decoder software or modifications thereof for use in hardware or software products claiming conformance to the standard. Copyright is not released for non MPEG-4 conforming products but the original developer retains full right to use the code for his own purposes and inhibit a third party from using the code for non MPEG-4 conforming products. ISO confirms that source code donators are relieved of any liability caused by third party use of their code in an implementation.

Model Copyright Disclaimer

(as amended in November 1996)

In the text <MPEG standard> should be replaced with the appropriate standard, e.g. MPEG-2 AAC (ISO/IEC 13818-7), MPEG-4 System (ISO/IEC 14496-1), MPEG-4 Video (ISO/IEC 14496-2), MPEG-4 Audio (ISO/IEC 14496-3) and MPEG-4 DMIF (ISO/IEC 14496-6).

<FN> = First Name, <LN> = Last name, <CN> = Company Name

"This software module was originally developed by <FN1> <LN1> (<CN1>) and edited by <FN2> <LN2> (<CN2>), <FN3> <LN3> (<CN3>), … in the course of development of the <MPEG standard>. This software module is an implementation of a part of one or more <MPEG standard> tools as specified by the <MPEG standard>. ISO/IEC gives users of the <MPEG standard> free license to this software module or modifications thereof for use in hardware or software products claiming conformance to the <MPEG standard>. Those intending to use this software module in hardware or software products are advised that its use may infringe existing patents. The original developer of this software module and his/her company, the subsequent editors and their companies, and ISO/IEC have no liability for use of this software module or modifications thereof. Copyright is not released for non <MPEG standard> conforming products. <CN1> retains full right to use the code for its own purpose, assign or donate the code to a third party and to inhibit third parties from using the code for non <MPEG standard> conforming products. This copyright notice must be included in all copies or derivative works. Copyright Ó 199_".