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Hi Ernesto,<br>
<br>
The "bitrate" option to the movie command creates a constant bit
rate encoding while the "qscale" option creates a variable bit rate
encoding. Generally a variable bit rate is better because it allows
the video to use a high bit rate when there is lots of motion and
low bit rate when there is little motion. This can produce the
highest quality with the smallest file size. So I recommend using
the qscale option. The qscale values range from 1 (highest quality)
to 31 (lowest quality) and the Chimera default if no qscale or
bitrate is given is qscale 8. I think 8 gives a medium quality in
most cases. It may depend on the video size in pixels. If you
specify qscale, then bitrate is ignored. My impression is that
qscale 3 or less gives very high quality. Of course higher quality
means bigger file size. So the quality choice depends on how you
will use your movie. If it is for viewing on the web you may need
to use a lower quality and smaller window size because the bandwidth
for your viewer may not be high enough, or they don't want to wait
for a large file to download. Likewise if you are using it as
supplementary material for a paper you might need to go with lower
quality or smaller window size so the download is not too slow. If
I am showing a video during a talk I sometimes use qscale 1 (very
highest quality) and large video size because my laptop can handle
the very high bit rate. I have the impression that PowerPoint tends
to choke playing large high bitrate videos but why PowerPoint
decides to refuse to play a video is always a mystery. You just
have to test it to know.<br>
<br>
Tom<br>
<br>
<br>
<blockquote type="cite">Hi Tom,<br>
<br>
Thank you so much for your quick reply. A 5000kb bitrate sounds
reasonable to you? Which value would you use for a medium-high
quality movie?<br>
<br>
Thanks again for your help and congratulations for the really good
job that you're doing with chimera.<br>
Ernesto.</blockquote>
<br>
<blockquote cite="mid:4F04A4B2.6050909@sonic.net" type="cite">
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Hi Ernesto,<br>
<br>
I see that Chimera daily builds are incorrectly giving the
option "-qscale 8" to ffmpeg, the program included in Chimera that
does the movie encoding. The "-qscale 8" conflicts and apparently
overrides the "-b 5000kb" bit rate setting you requested. Both
Chimera 1.5.3 and daily builds use qscale 8 which is variable bit
rate encoding if you do not specify bitrate. Recent changes to
Chimera movie defaults broke the movie quality handling. I have
fixed it. The fix will be in tonight's daily build, dated Jan 5
on the download page<br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.cgl.ucsf.edu/chimera/download.html#daily">http://www.cgl.ucsf.edu/chimera/download.html#daily</a><br>
<br>
Thanks for identifying the problem.<br>
<br>
Tom<br>
<br>
<blockquote
cite="mid:CAMfeskBUA=G_2MRPiGU9GhNR9P2EGc-reoh8fdEeSVuJFZWNiw@mail.gmail.com"
type="cite">Hi everyone,<br>
<br>
I've made some movies using the current Chimera alpha version
(alpha version 1.6 build 35109, 2011-12-24) in an ubuntu 10.04
laptop. I've noticed that the quality of the movies is worse
that in the version 1.5.3, and I have generated the movies using
the same chimera session and the same script. I've seen this for
at least avi and mp4 formats. <br>
<br>
The movie options I'm using in the script are:<br>
<i>movie record supersample 3<br>
movie encode output movie.avi bitrate 5000 framerate 25
mformat avi</i><br>
<br>
Does anybody know why the quality is worse in the newer Chimera
version?<br>
Thanks in advance,<br>
Ernesto.<br>
</blockquote>
<br>
<br>
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