Loudness adjustment for downmixed audio content
Audio content coded for a reference speaker configuration is downmixed to downmix audio content coded for a specific speaker configuration. One or more gain adjustments are performed on individual portions of the downmix audio content coded for the specific speaker configuration. Loudness measurements are then performed on the individual portions of the downmix audio content. An audio signal that comprises the audio content coded for the reference speaker configuration and downmix loudness metadata is generated. The downmix loudness metadata is created based at least in part on the loudness measurements on the individual portions of the downmix audio content.
1. A method for gain adjustments of audio signals based on encoder-generated loudness information, the method comprising:
receiving, by an audio decoder operating in a specific playback environment different from a reference channel configuration, an audio signal for the reference channel configuration, the audio signal including audio sample data and encoder-generated loudness metadata, the encoder-generated loudness metadata comprising a plurality of portions of loudness metadata for a plurality of playback environments, the plurality of portions of loudness metadata comprising one or more respective portions of loudness metadata for each playback environment in the plurality of playback environments;
selecting one or more portions of specific loudness metadata, based on the specific playback environment, from among the plurality of portions of loudness metadata for the plurality of playback environments, the one or more portions of specific loudness metadata relating to the specific playback environment;
determining loudness adjustment gains from the one or more portions of specific loudness metadata for the specific playback environment;
applying the loudness adjustment gains as a part of overall gains applied to the audio sample data to generate output audio data; and
applying loudness equalization to compensate an effect of a playback level on the tonal balance.
2. The method of claim 1 , wherein, the playback level is used to control one or more filters that are applied to a group of equalization filters.
3. The method of claim 2 , wherein the group of equalization filters are applied before and/or after the downmix.
4. The method of claim 2 , wherein the group of equalization filters is applied together with dynamic range control information and time-aligned with an equalized audio signal.
5. A non-transitory computer readable storage medium, storing software instructions, which when executed by one or more processors cause performing:
receiving, by an audio decoder operating in a specific playback environment different from a reference channel configuration, an audio signal for the reference channel configuration, the audio signal including audio sample data and encoder-generated loudness metadata, the encoder-generated loudness metadata comprising a plurality of portions of loudness metadata for a plurality of playback environments, the plurality of portions of loudness metadata comprising one or more respective portions of loudness metadata for each playback environment in the plurality of playback environments;
selecting one or more portions of specific loudness metadata, based on the specific playback environment, from among the plurality of portions of loudness metadata for the plurality of playback environments, the one or more portions of specific loudness metadata relating to the specific playback environment;
determining loudness adjustment gains from the one or more portions of specific loudness metadata for the specific playback environment;
applying the loudness adjustment gains as a part of overall gains applied to the audio sample data to generate output audio data; and
applying loudness equalization to compensate an effect of a playback level on the tonal balance.