IAMF Audio Elements supports various audio formats and layouts within a single media file, which can include popular codecs like AAC and MP3 as well as newer ones like Opus and Vorbis. This means that you can have high-quality surround sound for your main channels (like left, center, right, and height) while also including lower quality versions of the same content in other formats to accommodate different devices or bandwidth constraints.
For example, let’s say you have an input file with 5.1 surround sound audio that needs to be downmixed for playback on a stereo system. With Channel Grouping and Downmixing, IAMF Audio Elements can automatically generate a set of scalable audio channel groups with layouts that don’t include height channels (since they aren’t needed for stereo playback). This means you can have both high-quality surround sound and lower quality stereo versions in the same media file without any extra work or additional files.
In terms of downmixing, IAMF Audio Elements allows for various algorithms to be used depending on your needs. For example, you could choose a simple matrix-based approach that combines the left and right channels with the center channel to create a stereo output, or you could use more advanced techniques like binaural rendering or spatial audio processing to provide an immersive listening experience even in stereo mode.
Regarding recon gain, this feature is required only for scalable channel audio when there are multiple layers and when using Opus or mp4a codecs. It allows for the recovery of reduced sample values by applying a smoothed gain value to all de-mixed channels from the De-mixer module. The formula used for recon gain involves calculating the MA_gain, which is then multiplied with the current frame’s recon_gain value and applied to each audio sample using a hanning window function.
Overall, IAMF Audio Elements provides a flexible and powerful framework for handling different codecs and layouts within your media files, making it easy to create content that can be enjoyed on a wide range of devices and platforms without sacrificing quality or performance.
Regarding the Gain module in scalable channel audio processing: The Gain module is used to recover reduced sample values using output_gain(i) when its output_gain_is_present_flag(i) for Channel Group #i is set to 1. When it’s set to 0, then this module shall be bypassed for Channel Group #i. The value of output_gain(i) for Channel Group #i shall be applied to all samples of the mixed channels in Channel Group #i where a mixed channel means the channel audio for CL #n created by mixing multiple channels of an input channel audio when generating down-mixed audio from the input channel audio (i.e., the channel audio for CL #n).