WMS: Player Reports Recovered and Lost Packets (296103)


The information in this article applies to:

  • Microsoft Windows Media Services 4.0
  • Microsoft Windows Media Services 4.1
  • Microsoft Windows Media Player 6.4
  • Microsoft Windows Media Player 7
This article was previously published under Q296103

SUMMARY

Sometimes Windows Media Player reports a certain number of recovered and lost packets during the course of streaming audio or video. This article explains what this means and why the packets are recovered or lost.

MORE INFORMATION

Windows Media Player and Windows Media Services negotiate connections over Transmission Control Protocol (TCP) port 1755. This negotiation over TCP occurs for both TCP and User Datagram Protocol (UDP) streaming. When the player and server negotiate a connection using UDP as the transport for the Microsoft Media Server (MMS) protocol, they use TCP port 1755 for control data and a random UDP port in the range of 1024-5000 for the multimedia data.

UDP packets are numbered sequentially so that they can maintain their order when the stream is reassembled in the player. UDP is connectionless, so by design it cannot initiate a packet resend on its own. However, Windows Media Player is able to keep track of the packet sequence because it has a buffer value for receiving packets that contain multimedia data.

When it detects packets arriving out of order, Windows Media Player sends a re-transmission request to the server through the MMS channel (TCP port 1755). If the packet is received in time to render it in the player (that is, within the buffer settings for that stream), the packet is added in sequence and the stream plays smoothly. If the missing packets cannot arrive at the player within the buffer's timeout value, or if the client computer does not have sufficient system resources to render the packets in a timely manner, the packets are dropped and are reported as lost packets.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

240396 Packet Loss Reported In Player When Multi-Bitrate Is Multicasted

Modification Type:MajorLast Reviewed:11/26/2003
Keywords:kbinfo KB296103
©2003 Microsoft Corporation. All rights reserved.