[FFmpeg-devel] [DOC] FFSERVER Configuration Files.

[Michael Niedermayer]

Hi

On Wed, Aug 08, 2007 at 12:03:48PM -0700, Piero Bugoni wrote:
> 
> --- Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > On Wed, Aug 08, 2007 at 10:32:23AM -0700, Piero Bugoni wrote:
> > > 
> > > --- Michael Niedermayer <michaelni at gmx.at> wrote:
> > > 
> > > > > +#  Settings:
> > > > > +#
> > > > > +# The Q	value is pretty important here. Values of around 5 to 7.5
> > > > > +# give a reasonable compromise between stream width, and image quality.
> > > > > +# Make sure to match the settings in this file with those on the command line.
> > > > > +# in this instance values grater than 10 will probably make image indiscernable.
> > > > > +#
> > > > > +# Some additional settings for higher quality, but a fatter stream:
> > > > > +#
> > > > > +
> > > > > +# Qmin/Qmax=1, vbr~=12000, vbuf=52(min)
> > > > > +# Qmin/Qmax=2, vbr~=7100,  vbuf=33(min)
> > > > > +# Qmin/Qmax=3, vbr~=5200,  vbuf=22(min) good quality/stream compromise
> > > > > +# Qmin/Qmax=4, vbr~=4800,  vbuf=21(min)
> > > > > +# Qmin/Qmax=5, vbr~=4000,  vbuf=19(min)
> > > > > +# Qmin/Qmax=6, vbr~=3200,  vbuf=13(min)
> > > > 
> > > > constant qp encoding is not suitable for streaming over a channel with
> > > > limited bandwidth
> > > > 
> > > 
> > > OK.
> > > 
> > > (How limited)?  I have around 320Kb/s upload speed to the net.
> > 
> > you misunderstand
> > fixed qp encoding IS fundamentally not suitable for streaming, it does not
> > matter what bandwidth you have
> 
> Why is that?

because if you set qp high quality will be bad, if you set it low your
bandwidth will be insufficient if the video has the wrong content
your video might need the bitrates written above another might need 10x
the bitrate at the same qp (and i mean same resolution and framerate)


> 
> > if you do have 100mbit/sec you might get away with a 5 streams at constant
> > qp if the resolution isnt too high (dvd resolution or below)
> > 
> 
> Generally, the presumption with these files is that the resolution will be CIF size or smaller.
> 
> That being said, recommend some more appropriate Q values, and I will test them, and add them to
> the notes.
> 
> FFServer deals with QMin and QMax, but I do not know if a "QScale" option is available.
> 
> Recommend changes, and I'll put them in.

use bitrate and maxrate (and maxrate at least 30% higher than bitrate)
set qmin=2 qmax=31

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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