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[AR]n900 - Low latency webcam stream?

Hi.

I want make a argumented reality car, controled by n900 accelerometer.
So i have a embedded debian board with makes a wlan-accesspoint, controls the car and sends a webcam stream to n900.

I have testet videostream from my laptop webcam to n900 (server and client = vlc) with 3 different ways:

Code:

server rtp:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,acodec=mpga}:rtp{dst=CLIENTADRESSE,port=5000,sdp=file:///home/andi/sdp.sdp,ttl=10,mux=ts,proto=udp}'



client rtp:

open sdp.sdp file, generated by server

vlc file:///sdp.sdp

Code:

server udp multicast:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,vb=800,scale=1,acodec=mpga,ab=128,channels=2,samplerate=44100}:std{access=udp,mux=ts,dst=239.255.23.23:1234}'



client:

vlc udp://@239.255.23.23:1234 :udp-caching=0

Code:

server mms stream:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,vb=64,scale=1,acodec=mpga,ab=8,channels=1}:std{access=mmsh,mux=asfh,dst=:8080}'



client (n900, kmplayer, gstreamer/mplayer):

mms://SERVER:8080

via vlc:

vlc mmsh://SERVER:8080

My problem is, delay between webcam and n900(kmplayer/vlc) is ~2 seconds, thats too long.
Any ideas to decrase this latency?

Regards, Andi

Re: [AR]n900 - Low latency webcam stream?

try to send uncompressed video, that should help, but wifi might be too slow for it.

Re: [AR]n900 - Low latency webcam stream?

Quote:

Originally Posted by AndiThebest (Post 924235)

Code:

server rtp:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,acodec=mpga}:rtp{dst=CLIENTADRESSE,port=5000,sdp=file:///home/andi/sdp.sdp,ttl=10,mux=ts,proto=udp}'



client rtp:

open sdp.sdp file, generated by server

vlc file:///sdp.sdp

Code:

server udp multicast:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,vb=800,scale=1,acodec=mpga,ab=128,channels=2,samplerate=44100}:std{access=udp,mux=ts,dst=239.255.23.23:1234}'



client:

vlc udp://@239.255.23.23:1234 :udp-caching=0

Code:

server mms stream:

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp2v,vb=64,scale=1,acodec=mpga,ab=8,channels=1}:std{access=mmsh,mux=asfh,dst=:8080}'



client (n900, kmplayer, gstreamer/mplayer):

mms://SERVER:8080

via vlc:

vlc mmsh://SERVER:8080

My problem is, delay between webcam and n900(kmplayer/vlc) is ~2 seconds, thats too long.
Any ideas to decrase this latency?

Regards, Andi

u can use my tune-up utilities! it optimize network stack and install iptables and iproute. Other than that reduce color of webcam or compute all data onboard ( do u need a life image anyway ? ).

BTW: do u have fleury or hierholzer algo in php? i really need it!

Re: [AR]n900 - Low latency webcam stream?

thanks for fast replys!

Quote:

Originally Posted by aligatro (Post 924241)

try to send uncompressed video, that should help, but wifi might be too slow for it.

Its not possible to stream without transcoding... when i use vlc without the transcode parameter:

Code:

vlc -vvv v4l2:///dev/video0 --sout '#std{access=udp,mux=ts,dst=239.255.23.23:1234}'

I'll get this output:

Code:

[0x29e1f68] main mux debug: adding a new input

[0x29e1f68] mux_ts mux debug: adding input codec=YUY2 pid=68

[0x29e1f68] main mux error: cannot add this stream

[0x29eb958] main packetizer error: cannot create packetizer output (YUY2)

Quote:

Do you know how can i reduce quality and colors of the webcam? yes i want to have a life image.
btw: i am a php newbie ;)

Re: [AR]n900 - Low latency webcam stream?

i don't know. it should be some sort of freq filter on the server site. can't u just pipe video device through mplayer on server first i.e. preproccesing and then stream it with vlc? i don't have a fast algo here. also if u use my script u can get very low latency ping and upload dunno how much u can increase throughput but if u are really into it u should try it?

Re: [AR]n900 - Low latency webcam stream?

I didn't test this, but it might work.

Modified your server settings to

vlc -vvv v4l2:///dev/video0 --sout '#transcode{vcodec=mp1v,acodec=mpga,fps=10,vb=200} :rtp{dst=CLIENTADRESSE,port=5000,sdp=file:///home/andi/sdp.sdp,ttl=10,mux=ts,proto=udp}'

Frames per second is 10, bitrate is 200 kb/s and changed codec to Mpeg1.