BITSTREAM REPRESENTING AUDIO IN AN ENVIRONMENT

Abstract

:An (encoding) apparatus comprises a metadata generator (203) generating metadata for audio data for a plurality of audio elements representing audio sources in an environment. The metadata comprises acoustic environment data for the environment where the acoustic environment data describes properties affecting sound propagation for the audio sources in the environment. At least some of the acoustic environment data is applicable to a plurality of listening poses in the environment and the properties include both static and dynamic properties. A bitstream generator (205) generates the bitstream to include the metadata and often also audio data representing the audio elements for the audio sources in the environment. A decoding apparatus may comprise a receiver for receiving the bitstream and a renderer for rendering audio for the audio environment based on the acoustic environment data and on audio data for the audio elements.

Specification

WE CLAIM:
1. An apparatus for generating a bitstream, the apparatus comprising:
a metadata generator (203) arranged to generate metadata for audio data for a plurality of
audio elements representing audio sources in an environment, the metadata comprising acoustic
environment data for the environment, the acoustic environment data describing properties affecting
5 sound propagation for the audio sources in the environment, at least some of the acoustic environment
data being applicable to a plurality of listening poses in the environment and the properties including both
static and dynamic properties; and
a bitstream generator (205) arranged to generate the bitstream to include the metadata.
10 2. The apparatus of claim 1 wherein the acoustic environment data comprises a data group
describing a data format for at least part of a representation of property values for at least one property of
the properties affecting sound propagation and a plurality of data groups each comprising data describing
at least one property value using the representation.
15 3. The apparatus of any previous claim wherein the acoustic environment data comprises a
data group describing a frequency grid and a plurality of data groups each comprising data describing a
frequency dependent property of the properties using the frequency grid, and wherein the bitstream
comprises an indicator for indicating whether the bitstream comprises the data group describing the
frequency grid, and the data group comprises an indication of a format for data describing the frequency
20 grid, the data group comprising at least one of:
data providing an indication of a predetermined default grid;
data indicating a start frequency and a frequency range for at least some subranges of the
frequency grid; and
data indicating individual frequencies.
25
4. The apparatus of any previous claim wherein the acoustic environment data comprises a
data group describing an orientation representation format for representing orientation properties, and at
least one data group comprising data describing an orientation property of the properties using the
orientation representation format, the data group comprising at least one of:
30 data providing an indication of a predetermined default orientation representation;
data indicating a set of predetermined angles; and
data indicating angles on a quantized grid.

5. The apparatus of any previous claim wherein the acoustic environment data comprises a
first data field for first bits representing a value of a first property of the properties affecting sound
propagation and a second data field for an indication of whether the acoustic environment data comprises
5 an extension data field for second bits representing the value of a first property.
6. The apparatus of claim 5 wherein the second bits extend a range of possible values for the
first property.
10 7. The apparatus of claim 5 or 6 wherein the second bits increase a resolution of possible
values for the first property.
8. The apparatus of any previous claim wherein the metadata generator (203) is arranged to
generate the acoustic environment data to include a global indicator that the environment is a spatially
15 constrained environment and to restrict data values of the acoustic environment data to comply with a
predetermined restricted format for data values for the global indicator indicating that the environment is
spatially constrained.
9. The apparatus of any previous claim wherein the acoustic environment data includes an
20 animation indication for at least a first audio element, the animation indication indicating if at least one
property for the first audio element varies during a time interval; and the acoustic environment data for an
animation indication that the first audio element has at least one varying property comprises data
describing a variation of the at least one varying property.
25 10. The apparatus of any previous claim wherein the audio elements comprise a number of
sound effect elements and the acoustic environment data comprises data linking a user controlled change
to the environment with a first sound effect element of the number of sound effect elements

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