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View Full Version : Lag-free 802.11n audio bridge?




cube
Sep 13, 2009, 08:24 AM
I hadn't seen this forum, which is probably more appropriate.


http://forums.macrumors.com/showthread.php?t=784491



FX120
Sep 13, 2009, 05:49 PM
Good luck.

The human brain can tell when an audio track is off sync with the video by just a few milliseconds, and on average any WiFi traffic will be delayed by a few milliseconds at each point, not to mention the delay present in normal network traffic.

Your best solution is to find a way to delay the video to match, or just find a way to run copper.

ChrisA
Sep 13, 2009, 09:00 PM
You simply can't have lag free transmission over a network connection. The network puts data in "packets". The bits of audio data are placed into a packet and then when the packet is filled it is sent over the interface. The minimum delay depends on the audio bit rate and the packet size. But then in any but the most simple networks (all machines on one wired Ethernet) the packets after they are send go through one or more "store and forward" operations. There will always be some delay.

There are other ways to send audio that do not have this problem. But IP networks are packetized.

FX120
Sep 13, 2009, 10:34 PM
You simply can't have lag free transmission over a network connection. The network puts data in "packets". The bits of audio data are placed into a packet and then when the packet is filled it is sent over the interface. The minimum delay depends on the audio bit rate and the packet size. But then in any but the most simple networks (all machines on one wired Ethernet) the packets after they are send go through one or more "store and forward" operations. There will always be some delay.

There are other ways to send audio that do not have this problem. But IP networks are packetized.
Networked audio over copper/fiber is getting to the point where even layer 3 protocols can offer usable performance even with multiple channels, see DANTE as an example.

The problem here is the wireless part. Packet loss over a high-quality and properly installed copper cable is low and stays reasonable as distances increase due to the noise rejecting nature of the balanced pairs, but over WiFi packet loss is much more of an issue, and only gets worse as distances increase, SNR decreases, and interference has a greater impact on signal. Every time a packet is lost, it has to be re-sent, not only delaying the next packet in line and stacking the delay.