A data processing method comprises, using a media server during a first media session between a client device and the media server, determining a stable bitrate value for use as a rate of transmitting multimedia data from the client device to the media server; storing, in a database, the stable bitrate value for the client device in association with an identifier; receiving, from the client device, a request to establish a second media session; determining the identifier within the request; in response to the request, based on the identifier in the request, searching the database for the stable bitrate value that is associated with the identifier; in response to locating the stable bitrate value in the database, sending the stable bitrate value to the client device for use in estimating a bitrate for transmitting multimedia from the client device to the media server in the second media session; establishing, by the media server, the second media session, wherein the media server initially receives multimedia data from the client device at the stable bitrate.