The working group maintains a list of all bug reports that the editors have not yet tried to address; there may also be related open bugs in the [[MEDIA-SOURCE]] repository.

Implementors should be aware that this specification is not stable. Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should track the GitHub repository and take part in the discussions.

Introduction

This specification defines segment formats for implementations of [[!MEDIA-SOURCE]] that choose to support the ISO Base Media File Format [[!ISOBMFF]].

MIME-type parameters

This section specifies the parameters that can be used in the MIME-type passed to or .

MIME-types for this specification MUST conform to the rules outlined for "audio/mp4" and "video/mp4" in [[RFC6381]].

Initialization Segments

An ISO BMFF is defined in this specification as a single File Type Box (ftyp) followed by a single Movie Box (moov).

The user agent MUST run the if any of the following conditions are met:

1. A File Type Box contains a major_brand or compatible_brand that the user agent does not support.
2. A box or field in the Movie Box is encountered that violates the requirements mandated by the major_brand or one of the compatible_brands in the File Type Box.
3. The tracks in the Movie Box contain samples (i.e., the entry_count in the stts, stsc or stco boxes are not set to zero).
4. A Movie Extends (mvex) box is not contained in the Movie (moov) box to indicate that Movie Fragments are to be expected.

The user agent MUST support setting the offset from media composition time to movie presentation time by handling an Edit Box (edts) containing a single Edit List Box (elst) that contains a single edit with media rate one. This edit MAY have a duration of 0 (indicating that it spans all subsequent media) or MAY have a non-zero duration (indicating the total duration of the movie including fragments).

The user agent MUST support codec configurations stored out-of-band in the sample entry, and for codecs which allow codec configurations stored inband in the samples themselves, the user agent SHOULD support codec configurations stored inband.

For example, for codecs which include SPS and PPS parameter sets, for maximum content interoperability, user agents are strongly advised to support both inband (e.g., as defined for avc3/avc4) and out-of-band (e.g., as defined for avc1/2) storage of the SPS and PPS.

Valid top-level boxes such as pdin, free, and sidx are allowed to appear before the moov box. These boxes MUST be accepted and ignored by the user agent and are not considered part of the in this specification.

The user agent MUST source attribute values for id, kind, label and language for , and objects as described for MPEG-4 ISOBMFF in the in-band tracks spec [[INBANDTRACKS]].

Media Segments

An ISO BMFF is defined in this specification as one optional Segment Type Box (styp) followed by a single Movie Fragment Box (moof) followed by one or more Media Data Boxes (mdat). If the Segment Type Box is not present, the segment MUST conform to the brands listed in the File Type Box (ftyp) in the .

Valid top-level boxes defined in other than ftyp, moov, styp, moof, and mdat are allowed to appear between the end of an or and before the beginning of a new . These boxes MUST be accepted and ignored by the user agent and are not considered part of the in this specification.

The user agent MUST run the if any of the following conditions are met:

1. A box or field in the Movie Fragment Box is encountered that violates the requirements mandated by the major_brand or one of the compatible_brands in the Segment Type Box in this or the File Type Box in the if a Segment Type Box is not present.
2. This contains a Segment Type Box that is not compatible with the File Type Box in the .
3. The Movie Fragment Box does not contain at least one Track Fragment Box (traf).
4. The Movie Fragment Box does not use movie-fragment relative addressing.
5. External data references are being used.
6. At least one Track Fragment Box does not contain a Track Fragment Decode Time Box (tfdt)
7. The Media Data Boxes do not contain all the samples referenced by the Track Fragment Run Boxes (trun) of the Movie Fragment Box.
8. Inband parameter sets are not present in the appropriate samples and parameter sets are not present in the last initialization segment appended.

A Movie Fragment Box uses movie-fragment relative addressing when the first Track Fragment Run(trun) box in each Track Fragment Box has the data-offset-present flag set and either of the following conditions are met:

• Every Track Fragment Box in a Movie Fragment Box has the default-base-is-moof flag set.

  This implies that the base-data-offset-present flag is not set.

• The Movie Fragment Box contains a single Track Fragment Box and that box does not have the base-data-offset-present flag set.

Random Access Points

A as defined in this specification corresponds to a Stream Access Point of type 1 or 2 as defined in Annex I of .

Acknowledgments