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I have a cheap embedded linux NAS (a Seagate Central.) The device is certainly underpowered, but it's not entirely useless.

One thing that bugs me is that I can reliably copy a 300MB AVI file to my MacBook Air in 30 seconds (over WiFi) but if I try to watch that same file from the network share, after a few minutes of playback it locks the video player and the entire Finder.

This happens with both MPlayer OSX Extended and VLC; with various files; over both AFP and SMB. The video file that takes 30 seconds to copy is 30 minutes in playback time, so the network should be approximately 60 times faster than strictly needed. I've tried fiddling with the video players cache settings to no avail.

How would you debug this situation?

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  • "I can reliably copy ... in 30"" -- Thirty inches? Unless the context is a latitude/longitude, that's not a common symbol for a unit of time. – sawdust Sep 7 '14 at 23:45
  • I thought it was commonplace: ' = minutes, " = seconds. I edited the question. – Tobia Sep 8 '14 at 6:48
  • @Tobia No; outside of lat/long coordinates, when attached to numbers in English prose, ' is generally read to mean feet and " is likewise read to mean inches. – a CVn Sep 8 '14 at 7:15
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Copying a file and streaming it are two entirely different things.

Latency is one of the biggest stream killers. Run a ping to the NAS and see how long it takes to respond... run it for a few minutes... Is the repsonse time consistent?

Do you have a Thunderbolt to Ethernet adaptor? Try it over ethernet and see if the same problem occurs. Wifi introduces a lot of latency.

Next find out the bitrate of the video you are trying to stream. In VLC-> Window -> Media Information will show you the bitrate of the file. You could also open the Errors and Warnings window in the same menu and keep an eye on that.

Another way you can monitor the bitrate is by watching the network activity window in "Activity Monitor" (/Applications/Activity Monitor).

Do a speed test with BlackMagic Disk SpeedTest to your NAS drive to get an idea of the conistency and bandwidth you have available.

What version of OSX are you running? AFP has traditionally been faster but OSX 10.9 saw the implementation of SMB2 which improved performance drastically for devices that can support it.

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  • I'm running OS X 10.9, but unfortunately the crusty NAS does not have the latest Samba. I'll do the tests you suggested! – Tobia Sep 8 '14 at 6:50
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    @Tobia WiFi is also notorious for having lag that varies, due to on-the-air collisions. I would suggest running the ping also while copying the file (which stresses the network) and see what that does. If you see spikes then, consider moving to a different wifi channel and see if that helps; it's possible you're seeing the results of interference with a neighboring network. – a CVn Sep 8 '14 at 7:17

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