[Solved] RTP Streaming using VLC - Getting huge transmit UDP packet loss on my PC - why?

[yansi]

I am getting strange problems on my Windows 7 PC: I have tried to setup VLC media player to stream audio through RTP*, however I am getting huge outbound UDP packet lost.

*using "Audio CD" profile, only RTP (payload type 10, L16 Stereo 44100)

After some debugging, I observed, my PC can absolutely fine receive the same streamed packets from a different PC (no inbound UDP loss), however when my PC is set-up to transmit the stream, I get over 26% UDP packet loss. Even when PCs are connected using a straight piece of CAT5 cable.

From some Wireshark poking, it seems my PC does not even send those packets, at all. Something is preventing them to be sent. What might be causing it? I have no clue.

It doesn't matter if the stream is unicast or multicast. Results are the same, always about 1/4 packets are missing and probably never sent.

Thank you for any hints for what may have gone wrong.

[Rémi Denis-Courmont]

I'd be guessing that the bursts are overflowing the IP stack's buffers.

[yansi]

That's what I guessed too. However finding the solution wasn't easy. First I raised the transmit buffers in the network controller settings (that did nothing). Then I have researched about how to configure the windows IP stack, a found this, which worked a charm!

Code: Select all

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \Afd \Parameters] DefaultReceiveWindow = 65536 DefaultSendWindow = 65536

These two registry keys were missing completely on my machine, which leads to windows using the default buffer size of 8 kByte. I increased it to 64kB, which seems to have fixed the problem completely.

Please note that if this registry key is missing, windows uses the default size of 8kB.

Now I am wondering, how does this registry key look on another PCs. Will have a look.