[streaming] Re: Streaming bitrate tolerance (transcoding options)

[Benjamin Pracht]

On Wed, Jul 06, 2005, Martin Forget wrote :
> Hi everyone,
> 
> i am trying to HTTP stream live video to bandwidth limited (3Mbps  
> DSL) clients.
> 
> 
> i am using the following transcoding line:
> vlc -vv udp://@{some multicast mpeg2ts feed} --sout \
> "#transcode 
> {vb=1600,width=640,bframes=2,noise_reduction=250,vt=100000,bt=100000,  
> hq=rd,trellis,height=480,deinterlace,vcodec=mp4v,keyint=150,mpeg4_matrix 
> ,strict_rc}:std{access=http,mux=ts,url={myserver:port}}"
> 
> 
> this line gives me impressively good quality at average bitrates  
> around 1.6Mbps
> 
> this problem is during hard to encode scenes, instead of degrading  
> the video quality, the bitrate increases  to 3 or even 5Mbps
> (monitoring with iptraf)  which creates video hang on the 3Mbps dsl  
> clients.
> 
> i have tried a bunch of combinaisons of vt and bt arguments but both  
> don't seem to have any effect.
> 
> 
> Does anyone has advice on how to get a more CBR stream?
> 

Well, ffmpeg sometimes have hard times with rate control in single pass
when the amount of activity changes fast in a scene indeed. There is not
much I can advise you, excpet perhaps to further try to tune ffmpeg's
parametters.

Also, the your command line tends to indicate that you are using a 0.7.x
version of VLC. Could you please try with 0.8.2, and a recent version of
ffmpeg ?

-- 
BigBen

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