[MPlayer-users] udp sync over wifi

[Richard Markiewicz]

Ron Johnson <ron.l.johnson <at> cox.net> writes:

> 
> On 07/18/2012 02:19 PM, Richard Markiewicz wrote:
> > I'm evaluating the UDP sync feature of mplayer (1.1 release) on Windows.
> >
> > It's working great so far. My machines are wired on a gig-E network and
> > playback is perfectly in sync.
> >
> > I'd like to try it over WiFi. I tested with two machines:
> > - My desktop (master), wired to the network over gig-E
> > - My laptop (slave), connected wirelessly to the network over wireless G
> >
> > And performance is not good. In fact, it's nearly completely broken. The 
wifi
> > slave skips and jumps throughout the whole file.
> >
> > (I'm testing this scenario with a very simple, standard definition video 
that
> > the machines have no problem playing)
> >
> > Latency is very low on my wifi network. Ixia qcheck
> > (http://reviews.cnet.com/4520-6603_7-5020854-1.html) tests show that UDP
> > latency is around 1-3ms.
> >
> > So my question is - is wifi a supported/envisaged scenario? Is there an
> > underlying technical reason why this would not work? Perhaps some
> > configuration I can tweak that will help?
> >
> 
> Bandwidth is the first presumption.  802.11g has a max theoretical 
> throughput of only 6.75MBps, but can't actually reach that even at close 
> range with 5 bars.  What with router placement, distance from laptop to 
> router and what's in between the router and laptop, it gets worse very 
> quickly.
> 
> That's why I recently added a dual-band 802.11n router in AP mode 
> positioned more centrally in the building.  Note, though, that while 
> 5GHz N has much better bandwidth, it also has shorter range and is more 
> easily blocked than 2.4GHz.
> 

Thank you for your reply.

My understanding was that the datagram sent over the network contained only the 
time position within the file; and therefore should be quite small; and that 
latency was a bigger concern than bandwidth (from the man page: 
http://www.mplayerhq.hu/DOCS/HTML/en/networksync.html)

The measured latency on my network is (seems to be) very low. Have I made an 
incorrect assumption?

Thanks again