A method for metadata-preserved audio object clustering, comprising: classifying a plurality of audio objects into a number of categories based on information to be preserved in metadata associated with the plurality of audio objects; assigning a predetermined number of clusters to the categories; and allocating an audio object in each of the categories to at least one of the clusters according to the assigning, wherein the assigning the predetermined number of clusters to the categories involves determining, for each category, a respective number of clusters to be assigned to that category, such that the overall number of clusters adds up to the predetermined number of clusters; wherein the method further comprises: combining audio objects in each cluster to obtain a clustered audio object; combining metadata of audio objects in each cluster to obtain metadata of the clustered audio object; and rendering the clustered audio object and the associated metadata of the clustered audio object to produce an audio signal; and wherein the assigning the predetermined number of clusters to the categories comprises: assigning the predetermined number of clusters to the categories based on reducing an overall spatial distortion for the categories, or wherein the assigning the predetermined number of clusters to the categories comprises: determining a predetermined number of audio objects from the plurality of audio objects based on an importance of each audio object relative to other audio objects; determining distribution of the predetermined number of audio objects among the categories; and assigning the predetermined number of clusters to the categories according to the distribution. classifying a plurality of audio objects into a number of categories based on information to be preserved in metadata associated with the plurality of audio objects; assigning a predetermined number of clusters to the categories; and allocating an audio object in each of the categories to at least one of the clusters according to the assigning, wherein the assigning the predetermined number of clusters to the categories involves determining, for each category, a respective number of clusters to be assigned to that category, such that the overall number of clusters adds up to the predetermined number of clusters; wherein the method further comprises: combining audio objects in each cluster to obtain a clustered audio object; combining metadata of audio objects in each cluster to obtain metadata of the clustered audio object; and rendering the clustered audio object and the associated metadata of the clustered audio object to produce an audio signal; and wherein the assigning the predetermined number of clusters to the categories comprises: assigning the predetermined number of clusters to the categories based on reducing an overall spatial distortion for the categories, or wherein the assigning the predetermined number of clusters to the categories comprises: determining a predetermined number of audio objects from the plurality of audio objects based on an importance of each audio object relative to other audio objects; determining distribution of the predetermined number of audio objects among the categories; and assigning the predetermined number of clusters to the categories according to the distribution. combining audio objects in each cluster to obtain a clustered audio object; combining metadata of audio objects in each cluster to obtain metadata of the clustered audio object; and rendering the clustered audio object and the associated metadata of the clustered audio object to produce an audio signal; and wherein the assigning the predetermined number of clusters to the categories comprises: assigning the predetermined number of clusters to the categories based on reducing an overall spatial distortion for the categories, or wherein the assigning the predetermined number of clusters to the categories comprises: determining a predetermined number of audio objects from the plurality of audio objects based on an importance of each audio object relative to other audio objects; determining distribution of the predetermined number of audio objects among the categories; and assigning the predetermined number of clusters to the categories according to the distribution. assigning the predetermined number of clusters to the categories based on reducing an overall spatial distortion for the categories, or wherein the assigning the predetermined number of clusters to the categories comprises: determining a predetermined number of audio objects from the plurality of audio objects based on an importance of each audio object relative to other audio objects; determining distribution of the predetermined number of audio objects among the categories; and assigning the predetermined number of clusters to the categories according to the distribution. determining a predetermined number of audio objects from the plurality of audio objects based on an importance of each audio object relative to other audio objects; determining distribution of the predetermined number of audio objects among the categories; and assigning the predetermined number of clusters to the categories according to the distribution.