The Descriptor provides information about the Audio Substreams that will be included in this IA Sequence. Each Audio Substream is identified by a unique audio_substream_id, which can either be implicit (i.e., defined within the OBU payload) or explicit (i.e., provided as part of the Descriptor).
To apply gain parameters to Audio Elements during mixing using an AnimatedParameterData() function template, one can follow these steps:
1. Define a set of parameter values for each subblock (i.e., time interval) in which the gain will be applied. This is done by specifying start_point_value, control_point_value, and end_point_value using ParamDefinition() function templates within the AnimatedParameterData() function template.
2. Define a set of timing information for each subblock using ParamBlockOBUs. The timing information should include the start time (subblock_start_time) and end time (subblock_end_time) of each subblock, as well as any control point times (control_point_relative_times).
3. Apply the gain parameters to the audio samples in each subblock using either linear or Bezier interpolation based on the animation type specified by animation_type. If animation_type is equal to LINEAR, the set of parameter values is linearly interpolated between start_point_value and end_point_value at a given point in time as:
[gain = (1 t) * start_point_value + t * end_point_value]
4. If animation_type is equal to BEZIER, the set of parameter values is interpolated following a quadratic Bezier curve between start_point_value and end_point_value at a given point in time as:
[gain = (1 t) * ((1 s) * start_point_value + s * control_point_value) + t * ((1 r) * control_point_value + r * end_point_value)]
5. To apply the gain parameters to the audio samples in each subblock without interpolation, one can first resample the parameter values to match the sample rate of the audio using:
[n = floor((t * audio_sample_rate) / parameter_rate)]
6. Then, compute the equivalent value of t for every n and apply the Bezier equations or linear equation as necessary to find the gain value at that time.
In terms of selecting a Mix Presentation from multiple options based on specific requirements and constraints, one can follow these guidelines:
1. Identify the desired loudspeaker layout or spatialization algorithm for the IA Sequence. This will help narrow down the available Mix Presentations to those that best match your needs.
2. Consider any compatibility issues with a particular rendering or processing engine. If there are specific requirements for how the audio should be processed, make sure that the selected Mix Presentation is compatible with those requirements.
3. Evaluate the performance and quality of each available Mix Presentation using appropriate metrics such as loudness, distortion, and signal-to-noise ratio (SNR). This will help ensure that you select a high-quality mix presentation that meets your needs.
4. Test the selected Mix Presentation in a real-world environment to verify its performance and quality under actual conditions. This can help identify any issues or limitations that may need to be addressed before finalizing the selection.