We are sending an MPEG2-TS/H264 video stream over the network. This video stream is received correctly over the LAN, instead on the other end of a private WAN video quality is poor, thus suggesting packet loss over the network.

However video received on the other end of the WAN has the upper area of the image with good quality, and the lower area with poor quality (e.g. missing blocks) i.e. the first N lines of the image are always good quality (with N randomly changing).

Does this suggest the possible causes for the issue? E.g. if we were experiencing random packet loss, I expected random missing blocks across the whole image, why the first N lines are always good quality instead?

  • as video data rate is far below link capacity, we believe packet loss is not as severe as the poor quality may suggest Why would you believe that? If you need reliable data delivery, don't use UDP, especially across a WAN. Sep 7, 2017 at 13:35
  • @AndrewHenle issue here is not reliable vs unreliable data delivery. Issue here is what's the reason for poor video quality
    – kuma
    Sep 7, 2017 at 15:50
  • Issue here is what's the reason for poor video quality If poor quality is because of packet loss, that would be the actual definition of unreliable data delivery, now wouldn't it? Sep 7, 2017 at 16:52
  • @AndrewHenle Probably I wasn't able to convey what I am interested in. Edited the question. I don't understand why the first lines of the image are good quality if simple random packet loss is experienced
    – kuma
    Sep 8, 2017 at 8:15

1 Answer 1


I answer my own question hoping this may be useful for other users who had similar issues.

The machine streaming the video had a NIC configured at 1Gbps, while some of the links across the WAN were at 100Mbps.
Changing the configuration of the host NIC to 100Mbps solved the issue.
My guess is that the weird image quality (i.e. first N lines good quality while all other lines affected by noise) were due to the poor performances of software application in charge of video encoding, which probably sent video packets with peak bandwidth > 100Mbps, even if video data rate is much much lower (10Mbps).

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