Quoting James Almer (2023-12-05 23:43:55)
> diff --git a/libavutil/iamf.h b/libavutil/iamf.h
> new file mode 100644
> index 0000000000..bc0363153d
> --- /dev/null
> +++ b/libavutil/iamf.h
> +/**
> + * @file
> + * Immersive Audio Model and Formats API header
> + * @see <a href="https://aomediacodec.github.io/iamf/";>Immersive Audio Model
> and Formats</a>
> + */
> +
> +#include <stdint.h>
> +#include <stddef.h>
> +
> +#include "attributes.h"
> +#include "avassert.h"
> +#include "channel_layout.h"
> +#include "dict.h"
> +#include "rational.h"
> +
> +/**
> + * @defgroup lavf_iamf_params Parameter Definition
> + * @{
> + * Parameters as defined in section 3.6.1 and 3.8 of IAMF.
> + * @}
> + * @defgroup lavf_iamf_audio Audio Element
> + * @{
> + * Audio Elements as defined in section 3.6 of IAMF.
> + * @}
> + * @defgroup lavf_iamf_mix Mix Presentation
> + * @{
> + * Mix Presentations as defined in section 3.7 of IAMF.
> + * @}
> + *
> + * @}
> + * @addtogroup lavf_iamf_params
> + * @{
> + */
> +enum AVIAMFAnimationType {
> + AV_IAMF_ANIMATION_TYPE_STEP,
> + AV_IAMF_ANIMATION_TYPE_LINEAR,
> + AV_IAMF_ANIMATION_TYPE_BEZIER,
> +};
> +
> +/**
> + * Mix Gain Parameter Data as defined in section 3.8.1 of IAMF.
> + *
> + * Subblocks in AVIAMFParamDefinition use this struct when the value or
> + * @ref AVIAMFParamDefinition.param_definition_type param_definition_type is
> + * AV_IAMF_PARAMETER_DEFINITION_MIX_GAIN.
This is the wrong place for this second paragraph. IMO it should go into
doxy for either param_definition_type, or
AV_IAMF_PARAMETER_DEFINITION_MIX_GAIN.
> +/**
> + * Parameters as defined in section 3.6.1 of IAMF.
It's not immediately obvious how the contents are structured, so I'd
extend it with something like:
The struct is allocated along with an array of subblocks, which are
either AVIAMFMixGain, AVIAMFDemixingInfo, or AVIAMFReconGain depending
on the value of param_definition_type. This array is placed
subblocks_offset bytes after the start of this struct.
> + */
> +typedef struct AVIAMFParamDefinition {
> + const AVClass *av_class;
> +
> + size_t subblocks_offset;
Offset in bytes from the start of this struct, at which the subblocks
array is located.
> + size_t subblock_size;
Size in bytes of each element in the subblocks array.
> +
> + enum AVIAMFParamDefinitionType param_definition_type;
This struct is already called ParamDefinition, so this could be just
type. Also:
Parameters type. Determines the type of the subblock elements.
> + unsigned int nb_subblocks;
Number of subblocks in the array.
> +
> + unsigned int parameter_id;
> + unsigned int parameter_rate;
> + unsigned int param_definition_mode;
> + unsigned int duration;
> + unsigned int constant_subblock_duration;
These should be documented.
> +typedef struct AVIAMFLayer {
> + const AVClass *av_class;
> +
> + AVChannelLayout ch_layout;
> +
> + /**
> + * A bitmask which may contain a combination of AV_IAMF_LAYER_FLAG_*
> flags.
> + */
> + unsigned int flags;
> + /**
> + * Output gain channel flags as defined in section 3.6.2 of IAMF.
> + *
> + * This field is defined only if @ref
> AVIAMFAudioElement.audio_element_type
> + * "the parent's Audio Element type" is
> AV_IAMF_AUDIO_ELEMENT_TYPE_CHANNEL,
> + * must be 0 otherwise.
> + */
> + unsigned int output_gain_flags;
> + /**
> + * Output gain as defined in section 3.6.2 of IAMF.
> + *
> + * Must be 0 if @ref output_gain_flags is 0.
> + */
> + AVRational output_gain;
> + /**
> + * Ambisonics mode as defined in section 3.6.3 of IAMF.
> + *
> + * This field is defined only if @ref
> AVIAMFAudioElement.audio_element_type
> + * "the parent's Audio Element type" is AV_IAMF_AUDIO_ELEMENT_TYPE_SCENE.
> + *
> + * If AV_IAMF_AMBISONICS_MODE_MONO, channel_mapping is defined implicitly
> + * (Ambisonic Order) or explicitly (Custom Order with ambi channels) in
> + * @ref ch_layout.
> + * If AV_IAMF_AMBISONICS_MODE_PROJECTION, @ref demixing_matrix must be
> set.
> + */
> + enum AVIAMFAmbisonicsMode ambisonics_mode;
> +
> + /**
> + * Demixing matrix as defined in section 3.6.3 of IAMF.
> + *
> + * May be set only if @ref ambisonics_mode ==
> AV_IAMF_AMBISONICS_MODE_PROJECTION,
> + * must be NULL otherwise.
> + */
> + AVRational *demixing_matrix;
How many elements are in the array?
--
Anton Khirnov
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