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Vladimir Mosgalin wrote:
<blockquote cite="mid20050625112331.GA8453@VM10124.spb.edu" type="cite">
<pre wrap="">Hi Phil Oleynik!
On 2005.06.25 at 01:06:26 +0400, Phil Oleynik wrote next:
</pre>
<blockquote type="cite">
<pre wrap="">*max_key_interval
Usually, no one will need it. However, in some cases scene changes
very rarely. To save details sharpness one may try to lower its value
from default.
</pre>
</blockquote>
<pre wrap=""><!---->
It doesn't do anything useful.
</pre>
</blockquote>
Once, I have compressed very slow scene-changing animation with many
details in scenes.<br>
When I looked at graph of I/K-frames, I noticed that about 30 percent
of them are just because<br>
of timeout, not associated with real scene change. I set it to 500,
file became smaller, some percents.<br>
<blockquote cite="mid20050625112331.GA8453@VM10124.spb.edu" type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">*keyframe_boost
If you encode cartoon/anime, you will need it to get sharper edges
with the same bitrate.
</pre>
</blockquote>
<pre wrap=""><!---->
You might add that recommended value is around 15, 10-20 for me.
It doesn't really hurt on real life video, but doesn't help too. Great
for animation, yes.
</pre>
</blockquote>
I usually set it to 50 when source is of high quality, and result
should keep the same level. On real video,<br>
or when keyframes are very frequent, your value is more sane.<br>
<blockquote cite="mid20050625112331.GA8453@VM10124.spb.edu" type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">*kfreduction
No human is able do distinguish how bad rapid flashing frames were
compressed, but it is hard task for codec. With this option only the
last frame from series of flashes will get full bitrate.
</pre>
</blockquote>
<pre wrap=""><!---->
I don't really understand why, but a lot of people advice to use 24 for
23.976/24/25 fps video and 30 (default) for 29.97/30 fps video.
</pre>
</blockquote>
This is quality percent-divisor, 24 and 30 it is maybe for kfthreshold?
<blockquote cite="mid20050625112331.GA8453@VM10124.spb.edu" type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">*(no)packed
One of best XviD features, frame swapping. If this is turned on, codec
will try to swap frames in order to get more quality. Price here is
DivX compatibility.
*(no)closed_gop
This option also may break compatibility. However, it may save a few bits.
</pre>
</blockquote>
<pre wrap=""><!---->
One of this options (or both, don't remember) actually break lavc
compatibility, it will display file with errors (maybe fixed in newer
versions, but..). They may reduce file a bit, but it doesn't worth it.
</pre>
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<pre wrap="">*qpel
Option, that should be used for high quality streams, it may do good,
or may do bad to your movie. Highly dependent from source material.
</pre>
</blockquote>
<pre wrap=""><!---->
Maybe it was me, but I never found cases where it was useful - not with
xvid, nor with lavc. The quality is always lower or at least the same.
</pre>
<blockquote type="cite">
<pre wrap="">*gmc
Also, highly dependent from source material. If you have many
panoramic scenes, this will save a great amount of bits using XviD
pan/zoom compressing features. This will make your movie decode slower
(640*480 24fps pan scene may become too hard for Celeron III 800, my
own exp.)
</pre>
</blockquote>
<pre wrap=""><!---->
Again, I tested it on a lot of material, it never helped.. though it
doesn't usually waste a lot of bitrate too, so the picture stays about
the same.
But maybe it would help in very low bitrate cases, I never tested this.
</pre>
</blockquote>
It helps great, when camera moves right-left-right-left-right... Slowly
and with sense, i.e. interframes<br>
are to be seen clear.<br>
<br>
<br>
Philipp<br>
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