Streaming through 802.11b (WLAN)

[systest]

I want to use VLC to stream mpeg4 video through 802.11b. Following is my step:

1. Connect PC server with VLC (0.8.2/Linux) to a switch with multicast support
2. Use VLC to stream video to a multicast address (UDP)
3. Connect my laptop to the multicast switch, use VLC as client to receive multicast stream, it's OK, can play the stream normally.
4. Add an wireless AP to the multicast switch, at same time, disconnect the wire connection between switch and my laptop.
5. Use wireless card on my laptop to connect to the AP, ping the PC server(VLC streaming), get correct response.
6. Use VLC(on my laptop) as client to receive multicast stream, it can't work, can't access the multicast address, why?

PS: in the same topology, MS's media server/player can work normally, if VLC doesn't has a perfect multicast support?
Pls give me some suggestion!

[dionoea]

multicast over wireless networks usually doesn't work (and kills most APs)

[systest]

why? Any patch for this issue?

Or did you know which AP can provide a perfect support for multicast over wireless LAN?

[systest]

Now, multicast over 802.11b is OK(I change my laptop WLAN driver). The clicent side VLC can receive the SAP info and multicast video stream from wireless LAN, but the performance is too low, in log, "discontinuously received xxx" alway show.

But MS's multicast streaming solution(wmencoder/media service/media player) can touch a good performance on the same wireless LAN.

Is this the problem of my AP? Do you know any kind of AP can provide perfect support for multicasting over 802.11?
Following is a part of log file, FYI.

Code: Select all

main debug: looking for packetizer module main debug: probing 17 candidates packetizer_mpeg4video debug: opening with vol size:55 main debug: using packetizer module "packetizer_mpeg4video" main debug: thread 3672 (decoder) created at priority 0 (src/input/decoder.c:157) ts debug: * descriptor : unknown (0x1f) ts warning: first packet for pid=69 cc=0xb ts warning: discontinuity received 0x7 instead of 0x1 ts warning: discontinuity received 0x2 instead of 0x1 ts warning: discontinuity received 0x7 instead of 0x3 ts warning: discontinuity received 0x5 instead of 0x2 ts warning: discontinuity received 0xa instead of 0x8 ts warning: discontinuity received 0xe instead of 0xb ts warning: discontinuity received 0x8 instead of 0x5 ts warning: discontinuity received 0x2 instead of 0xf ts warning: discontinuity received 0xc instead of 0x9 ts warning: discontinuity received 0x7 instead of 0x3 ts warning: discontinuity received 0x4 instead of 0xb ts warning: discontinuity received 0x1 instead of 0xd

[The DJ]

VLC doesn't do packet reordering. perhaps MS does. I have no idea, because multicast with MS requires you to pay a ton for the WMserver, so i know no one who really ever tested with it. Also they use an encrypted (NSC) format announce, which to my knowledge so far hasn't been cracked.

Increasing buffering on client and server side of VLC might improve the situation a bit.

Still multicast on WLAN points is bull. You might just as well use unicast. (The AP still needs to setup seperate connections to each and every endpoint).

[jgg]

Hi there,

I recover this thread just to ask one question. I am having the same problem with 802.11g wireless networks. Unicast is received properly but multicast video playing is choppy with multiple "Discontinuity at reception" messages.

It has been said that VLC doesn't do any packet reordering and maybe with MS software it is done. I would like to know if this (VLC not reordering packets) applies for both unicast and multicast streaming or only to multicast (as unicast streaming works properly in the same networks where multicast is choppy).

I would like to know as well if anybody has checked that these multicast streaming errors only happen with VLC (so packet reordering might be the cause).


Thanks a lot.

[lowrid3r]

Hy, sorry for my English

I have the same problem.
I have a server computer and Airlive WH-5400CPE Access Point, witch connect to my switch. I want transfer video through 802.11g, to three other machine. Each of them connect to Airlive WH-5400CPE Client, there is a picture how it looks:

I could transfer video at http and udp/rtp unicast with perfect quality. The multicast worked too, but the quality was horrible.
The most important, why happend that and how could i fix it, if it possible?

Thanks.

[jgg]

Hi,

It seems there's no way to do it by now. Radio channel introduces lots of lost packets in multicast transmissions and, as there is no acknowledgment system from the access point to the client devices, there is no way to recover lost packets.

In order to improve the quality you should implement a reliable transport system based on FEC algorithms (like FLUTE protocol) or a acknowledgment procedure to deploy in this kind of transmissions.

However, that's why current 802.11 specifications are not prepared for video streaming services. Maybe 802.11n, WiMAX or MBMS for cellullar networks.

Good luck.

[lowrid3r]

Thanks the answer man, but i try to fix it.

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