> Date: Wed, 16 Apr 2008 02:08:29 +0200> From: [EMAIL PROTECTED]> To:
> [email protected]> Subject: Re: [libav-user] quality of encoding> > Hi
> Jasper,> > Jasper Leemans wrote:> > ---------------------------------------->
> > > >> Date: Tue, 15 Apr 2008 11:23:26 -0400> >> From: [EMAIL PROTECTED]> >>
> To: [email protected]> >> Subject: Re: [libav-user] quality of
> encoding> >>> >> Jasper Leemans a écrit :> >> > >>> Hi all,> >>>> >>> I`m
> encoding raw frames to an mpeg1 stream and I`m just wondering,> >>> is there
> a way to raise the quality, for example through the codec context> >>>> >>>
> c->quality = ...> >>>> >>> or lower the compression ratio.> >>>> >>> I can`t
> find anything similar in the c example code.> >>>> >>> wkr,> >>>> >>> Jasper>
> >>> _________________________________________________________________> >>>
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> https://lists.mplayerhq.hu/mailman/listinfo/libav-user> >>> > >>> > >> Hi> >>
> The first thing you should check is the bitrate. I think that by default > >>
> it's 200 kb/s. By increasing the bitrate you will for sure increase the > >>
> quality.> >> The compression ratio, by decreasing the gop you will add more
> key > >> frames and therefore have better quality there too.> >>> >> I would
> like to have feedback on this.> >> > >> >> > I decreased the gop from 10 to
> 1,> > I also changed the bitrate from 400kbit to 1000kbit, I notice these
> things:> >> > 1) when looking at the mpeg file info the bitrate went from
> 2600kbit to 3000kbit/s,> > so setting the bitrate with c->bitrate seems to
> have no real effect for me,> > as I seem to have no real control over it, it
> ignores the bitrate I set.> >> > 2) the file got bigger but I see no
> noticeable visual improvement.> > > > Always change _one_ parameter at the
> time to see what it influences...> > So, you should have kept the GOP-size at
> 10 and only modified the > bitrate. That should have shown a visual
> improvement, _except_ when the > bitrate is too low and libavcodec will use a
> higher bitrate anyway. So, > it also depends on the resolution of the video
> you are encoding: If you > were encoding 720p video, 400kbit would be way too
> low and changing it > wouldn't change much, as libavcodec would have probably
> used something > higher then 400kbit in the first run anyway.
Yes if I set it too low, or not at all, he outputs between 2 and 3 mbit,
I set it to 5mbit/sec, it works and with a big visual improvement,
thanks.
> > And, I have to disagree with the statement that decreasing the GOP >
> > increases the quality. Especially the way you are using it now. You've >
> > (almost) turned your MPEG encoder into an MJPEG encoder which will >
> > decrease the compression ratio, and therefore, for a certain fixed >
> > bitrate you'll get less quality.> > With friendly regards,> Takis>
> > _______________________________________________> libav-user mailing list>
> > [email protected]>
> > https://lists.mplayerhq.hu/mailman/listinfo/libav-user
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