[MPlayer-users] udp sync over wifi

[Ron Johnson]

On 07/19/2012 08:12 AM, Richard Markiewicz wrote:
> 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?
>

You can test it by plugging the laptop into the wired net.

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