Playing video on a Windows server via rdesktop often results in audio and video being out of sync. Exactly how out of sync seems to vary with the video, but it ranges from just noticeable to a second or so. Historically this has been a protocol limitation, but Microsoft's own client does not exhibit the same issues so it is possible to do better. Test cases are Youtube in IE and Firefox, and Windows Media Player. Seen with both Windows 2012 R2 and Windows 2016.
A casual glance shows no new audio protocol, but there are references to syncing in the new video extension: [MS-RDPEVOR]: Remote Desktop Protocol: Video Optimized Remoting Virtual Channel Extension https://msdn.microsoft.com/en-us/library/hh554658.aspx "hnsTimestamp (8 bytes): UINT64 ([MS-DTYP] section 2.2.50). Timestamp of the current packet, in 100-ns intervals since the video presentation was started. This timestamp SHOULD be used to sync the video stream with an audio stream remoted using the Remote Desktop Protocol: Audio Output Virtual Channel Extension (see the dwAudioTimeStamp field in [MS-RDPEA] section 2.2.3.10)."
rdesktop (and associated tools) is being removed from the ThinLinc product.
