[ziffius]

I believe this is the part of the DLNA spec in question if it's of interest to anyone:

Media Format and Transport Model

The DLNA media format model is intended to achieve a baseline for network interoperability while encouraging continued innovation in media codec technology. Improvements in media codec technology result in better network bandwidth utilization and media quality for a given bit rate. DLNA requirements on media format support apply to media content that passes over the home network from a DMS or M-DMS device to a DMP or M-DMP device. The DLNA media format model defines a set of required media formats and a set of optional media formats for each of the three classes of media and for both device categories: image, audio, and video with audio (AV). Table 1 and Table 2 show the current set of required formats and optional formats as defined in the DLNA guidelines. The network interoperability model for media formats is as follows:

• All DMS, DMP, DMR, DMC, and DMPr devices, and their counterpart MHD devices, must support all formats designated in Table 1 and Table 2 as required for any of the media classes and device category they support. In the addition, all DMS/M-DMS and DMP/M-DMP/M-DMD devices may support any additional formats designated as optional for any of the media classes they support.

• Any DMP, M-DMP, DMR, M-DMD and DMPr device must be able to receive content from any DMS or M-DMS device. A DMS or M-DMS device may stream content in its native format if the receiving device supports such native format. Otherwise, that DMS or M-DMS device should transcode the native format to one of the applicable required formats or to a format understood by the rendering device.