TS discontinuity messages

[irkuck]

I downloaded latest vlc version
0.7.2-test2 and it plays fine in multicast over my home network.
Pictures are perfect, absolutely no loss of packets.

But to my surprise when I open
Add interfac->Console I see lots of messages like:

libdvbpsi error (PSI decoder): TS discontinuity (received 11 expected 9)

Messages are coming all the time and the numbers change.

Since I see no packet loss, what might be the reason for these messages?

[The DJ]

Some packets are delayed. VLC doesn't reorder UDP packets and when they arrive out of order, the ones that are late are just skipped by VLC. When you use good network equipment, they should be pretty much in the same order as they were sent, but UDP simply doesn't guarentee anything about the order in which UDP packets arrive and even not if they will arrive at all. To guarentee everything will arrive as it should you need to use tcp however then you cannot multicast

[irkuck]

I believe I have very good network equipment: HP 2524 hardware switch
with no other load and multicast set as high priority

If there would be packet loss I would see it as distortions on screen, but pictures are always perfect and there is
absolutely no loss visible

This leaves to me packet order as explanation. Is it so that using the RTP layer packets are reordered on the receiving side so even if they are coming in wrong order this is corrected

[The DJ]

Not with vlc, VLC does no packet reordering whatsoever. it just skips the ones that are late.

[Guest]

Not with vlc, VLC does no packet reordering whatsoever. it just skips the ones that are late.

Hmmm, so this would mean there is packet loss, but I don't see any erros made by it. Where is the
catch then

[The DJ]

There is no packet loss in the network, just incorrect order. Therefore VLC drops packets. That's why you get the TS discontinuity warnings.

[irkuck]

There is no packet loss in the network, just incorrect order. Therefore VLC drops packets. That's why you get the TS discontinuity warnings.

But if vlx drops packets then I would see errors in video, right?
But I don't.

[sash]

I would say that all depends on how big of packet you are sending. it could range from a frame to a alot frames I would adjust the packet size to some thing that runs the smoothest on your network. because I have broadcast HDTV over a network to another computer for broadcast viewing and I would loose very few frames if any.. but I would say it is a matter of balancing packets for your network situation

[Guest]

because I have broadcast HDTV over a network to another computer for broadcast viewing and I would loose very few frames if any.. but I would say it is a matter of balancing packets for your network situation

I am multicasting HDTV stream from
satellite in my home LAN which is not loaded and I have switch which is supposed to be very good. I get reports from vlc about packet loss in demux and this is probably because my client PC is loaded 100% when decoding HDTV. So this is OK.

But I never see packet loss ín decoded video on screen. I wonder why? It should be that occasionally important packet gets lost resulting in visible artefacts.

[balazer]

If VLC is truly dropping out-of-order UDP packets, then this is a huge flaw, and a broken implementation of a streaming UDP protocol. Packet order is simply not guaranteed with UDP, and the further apart the client and server are, the more likely packets are to be out of order.

It is the application's responsibility to buffer and re-order packets on the receiving end.

[The DJ]

The necessity of packet reordering is greatly exagerated.
I watch MPEG2 DVD streams over hundreds of km's without any visible artefacting. packetreordering lays a huge extra effort at the client side which in many cases is just not neceserry. Still having the option would be nice of course. I just don't think anyone requires it atm.

[evert]

I'm also getting these errors/warnings, but also no video at all! Does that mean there are too many discontinuities, or would the problem be elsewhere?