Audio Channel Layout
A structure that defines the roles, spatial positions, arrangement, and playback relationships of audio channels is not the same as the number of channels in a file or the number of physical speakers.
Explanation
音频声道布局 Describes the roles and intended spatial positions of a set of channels, such as left, right, center, surround, top, and low-frequency effects. Simply recording “six channels” is insufficient to distinguish between 5.1, six independent mono channels, bilingual multitracks, or other arrangements; therefore, media formats typically also require channel masks, labels, or a default order specified by standards.
Layout, channel order, and speaker configuration are three related but distinct concepts. Layout describes semantics; order describes the arrangement of data in a bitstream or file; and speaker configuration describes the actual playback equipment. Different containers and interfaces may use different orders for the same 5.1 setup, and incorrect mapping can send the center, LFE, or surround channels to the wrong positions.
LFE and bass management should also be distinguished. LFE is a separate effects channel within the program, whereas bass management redirects low-frequency content from any main channel to a subwoofer based on speaker capabilities. The `.1` in the layout does not account for a physical subwoofer, nor does it imply that other channels lack low-frequency content.
Object-based and scene-based audio further decouple the program representation from fixed speaker configurations. Objects are positioned by metadata and then mapped to the actual layout by the renderer; the final device may display an output configuration such as 5.1.4, but the original audio stream does not necessarily contain only the corresponding number of fixed channels. When describing the database, the source layout, encoding format, and actual rendered layout should be stored separately.