ISO BMFF Byte Stream Format

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

It defines the MIME-type parameters used to signal codecs, and provides the necessary format specific definitions for initialization segments, media segments, and random access points required by the Byte Stream Formats section of the Media Source Extensions™ specification.

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

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

An ISO BMFF initialization segment 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 append error algorithm 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.

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 initialization segment in this specification.

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

An ISO BMFF media segment 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 initialization segment.

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

The user agent MUST run the append error algorithm 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 media segment or the File Type Box in the initialization segment if a Segment Type Box is not present.
2. This media segment contains a Segment Type Box that is not compatible with the File Type Box in the initialization segment.
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.
  Note

  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.

A random access point as defined in this specification corresponds to a Stream Access Point of type 1 or 2 as defined in Annex I of [ISOBMFF].

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words MAY, MUST, and SHOULD in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.