MPEG_buffer_circular
Contributors
- ISO/IEC SC29 WG3 (MPEG Systems) - Scene Description Breakout Group
- Contacts
- Thomas Stockhammer (MPEG-I Scene Description BoG Chair, tsto@qti.qualcomm.com)
Status
Based on ISO/IEC FDIS 23090-14
Dependencies
Written against the glTF 2.0 spec.
glTF Schema Updates
In order to support timed data access, the buffer element is extended to provide functionality of a circular buffer. The MPEG_buffer_circular may be included as part of the buffer. buffer that provides access to timed data shall include the MPEG_buffer_circular extension.
MPEG_buffer_circular Properties
| Type | Description | Required | |
|---|---|---|---|
| count | integer | This provides the recommended number of sequential buffer frames. | No, default: 2 |
| media | integer | The index of the media entry in the MPEG_media extension | ✓ Yes |
| tracks | integer [1-*] | The array of indices of tracks the MPEG_media entry. | No |
| extensions | object | JSON object with extension-specific objects. | No |
| extras | any | Application-specific data. | No |
Additional properties are allowed.
- JSON schema: MPEG_buffer_circular.schema.json
MPEG_buffer_circular.count
The count field provides the recommended number of sequential buffer frames to be offered by a circular buffer to the presentation engine. This information may be used by the application to setup the circular buffer towards the presentation engine.
- Type:
integer - Required: No, default:
2 - Minimum: ` >= 2`
MPEG_buffer_circular.media
Index of the media entry in the MPEG_media extension, which is used as the source for the input data to the buffer.
- Type:
integer - Required: ✓ Yes
- Minimum: ` >= 0`
MPEG_buffer_circular.tracks
The array of indices of a track of a media entry, indicated by media and listed by MPEG_media extension, used as the source for the input data to this buffer. When tracks element is not present, the media pipeline should perform the necessary processing of all tracks of the MPEG_media entry, referenced by the media property, to generate the requested data format of the buffer. When tracks array contains multiple tracks, the media pipeline should perform the necessary processing of all referenced tracks to generate the requested data format of the buffer. If the track attribute is present and there are multiple alternatives (i.e. indicating equivalent content) in the referenced media, then the selected track shall be present in all alternatives. When more than one track is listed by tracks element, the corresponding buffer is in active state and the application is informed that the corresponding tracks are needed as source for the input buffer, then the application can optimize the delivery of multiple tracks.
- Type:
integer[1-*]- Each element in the array MUST be greater than or equal to
0.
- Each element in the array MUST be greater than or equal to
- Required: No
MPEG_buffer_circular.extensions
JSON object with extension-specific objects.
- Type:
object - Required: No
- Type of each property: Extension
MPEG_buffer_circular.extras
Application-specific data.
- Type:
any - Required: No
Known Implementations
Resources
- ISO/IEC FDIS 23090-14, Information technology — Coded representation of immersive media — Part 14: Scene Description
- ISO/IEC WD 23090-24, Information technology — Coded representation of immersive media — Part 24: Conformance and Reference Software for Scene Description for MPEG Media
License
Copyright ISO/IEC 2022
The use of the “MPEG scene description extensions” is subject to the license as accessible here: https://standards.iso.org/ and is subject to the IPR policy as accessible here: https://www.iso.org/iso-standards-and-patents.html.