An audio mixer on a first device receives one or more incoming audio streams. Each of the one or more incoming audio streams has an associated timestamp. The audio mixer generates a mixed audio stream from the one or more incoming audio streams. The audio mixer determines differences in the time base of each of the one or more incoming audio streams and the time base for the mixed audio stream. The audio mixer generates mapping parameters associated with the determined differences and transforms the timestamp of each of the one or more incoming audio streams to a corresponding output timestamp associated with the mixed audio stream according to the mapping parameters. the mapping parameters are provided to a video mixer for similar processing and transformation such that the mixed audio stream is in synchronization with a mixed video stream.