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From: Orchid XP v8
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 23 Aug 2008 14:42:00
Message: <48b059f8@news.povray.org>
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Stephen wrote:
> On 23 Aug 2008 13:24:35 -0400, Warp <war### [at] tag povray org> wrote:
>
>> (Another issue is that creating an mpeg video (regardless of the mpeg
>> version) is not an unambiguous process. Some mpeg codecs are able to
>> create noticeably better image quality at the exact same file sizes
>> than other, lower-quality codecs.)
>
> Would you expand on this, Warp?
The MPEG standard specifies *exactly* how to decode an MPEG file into
something that can be displayed. However, it leaves several parts of the
*encoding* process open to interpretation.
At least, that is my understanding of it.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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From: Warp
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 23 Aug 2008 15:06:31
Message: <48b05fb7@news.povray.org>
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Stephen <mcavoysAT@aoldotcom> wrote:
> > (Another issue is that creating an mpeg video (regardless of the mpeg
> >version) is not an unambiguous process. Some mpeg codecs are able to
> >create noticeably better image quality at the exact same file sizes
> >than other, lower-quality codecs.)
> Would you expand on this, Warp?
Let me present a closely related example:
A compressed zip file format is very well specified, and thus there are
tons of programs which can read zip files. However, *creating* the zip
file is far from unambiguous. There is no one single definitive perfect
algorithm to create an optimally minimal zip file for any given data.
For this reason there exist zip optimizer programs (such as for example
advzip) which do a better job than the basic zip compressor programs
(such as WinZip or Windows Explorer).
Creating an mpeg file is similarly ambiguous. There is no one single
optimal algorithm to do so, and thus some codecs do a better job than
others.
--
- Warp
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On 23 Aug 2008 15:06:31 -0400, Warp <war### [at] tag povray org> wrote:
>
> Creating an mpeg file is similarly ambiguous. There is no one single
>optimal algorithm to do so, and thus some codecs do a better job than
>others.
Sorry, I expressed myself badly. I was wondering which codices are the better
ones and which ones to avoid, for the windows platform.
--
Regards
Stephen
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On Sat, 23 Aug 2008 19:42:04 +0100, Orchid XP v8 <voi### [at] dev null> wrote:
>
>The MPEG standard specifies *exactly* how to decode an MPEG file into
>something that can be displayed. However, it leaves several parts of the
>*encoding* process open to interpretation.
>
>At least, that is my understanding of it.
Thanks Andrew but ... (see below :)
--
Regards
Stephen
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From: Darren New
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 24 Aug 2008 11:28:06
Message: <48b17e06$1@news.povray.org>
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Orchid XP v8 wrote:
> The MPEG standard specifies *exactly* how to decode an MPEG file into
> something that can be displayed. However, it leaves several parts of the
> *encoding* process open to interpretation.
Yep. And the parts that are left open are difficult to implement. For
example, one of the decoding commands is "take the block of pixels from
X1,Y1 in the previous frame and draw them at X2,Y2 in this frame."
(Called something like "motion compensation".) Which means you have to
look all over the current frame to try to find a block of pixels that
matches the previous frame somewhere. Works well for fast-moving
objects, like a car driving past, but computationally expensive.
Plus, there's I frames, P frames, and B frames. Normally it's encoded
something like
IbbPbbPbbIbbPbbPbbI....
where the I frames are basically jpeg, the P frames are differences from
the I frames, and the B frames are differences from both the previous
frame and the following frame. Lots and lots of encoders only go one
direction, so they don't even generate B frames, which are usually far
smaller than the other two types of frames. (The I frames are the ones
you can seek to, and the P frames are the ones you can show when you
"fast forward" basically. Usually, I frames are twice a second or so.)
You can check pretty easily by trying to compress some video that's
flattish (like, looking into cloudy water, say) and some that's moving
fast in lots of directions (like explosions) and see if you see artifacts.
--
Darren New / San Diego, CA, USA (PST)
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From: Darren New
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 24 Aug 2008 12:15:17
Message: <48b18915@news.povray.org>
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Darren New wrote:
> where the I frames are basically jpeg, the P frames are differences from
> the I frames,
Differences from the previous I frame only, that is... :-)
--
Darren New / San Diego, CA, USA (PST)
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From: scott
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 25 Aug 2008 02:53:56
Message: <48b25704$1@news.povray.org>
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> Sorry, I expressed myself badly. I was wondering which codices are the
> better
> ones and which ones to avoid, for the windows platform.
I use the h264 codec for high qualitiy high resolution videos from POV:
http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC
For Windows (and other OSs I guess) you can use a free program called x264
to make them.
http://en.wikipedia.org/wiki/X264
Or, if you don't like fiddling around with command line options (and there
are *a lot* for encoders like this) there are plenty of GUIs around. I
often use xvid4psp as it contains built-in profiles for making h264 videos
compatible with things like the PS3, xbox, PSP etc (it can be fiddly trying
to find out exactly which command line options are needed to make a video
file compatible with these devices).
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From: scott
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 25 Aug 2008 02:56:06
Message: <48b25786$1@news.povray.org>
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> It's not a question of how difficult it would be to implement. It's a
> question of whether you want povray to support creating lossy output or
> not. Nothing would be more aggravating than starting your final render,
> waiting 50 hours for it to finish, and then notice that you used the
> wrong compression settings and your video looks like absolute crap.
> At least if you have the lossless original frames, you can re-encode
> easily without having to re-render.
>
> (Another issue is that creating an mpeg video (regardless of the mpeg
> version) is not an unambiguous process. Some mpeg codecs are able to
> create noticeably better image quality at the exact same file sizes
> than other, lower-quality codecs.)
Sure, but of course the option of outputting individual frames shouldn't be
removed, it could just be another option. Would be useful, especially for
short quick-to-render animations. FOr the Windows version POV could just
give you a choice to use any currently installed codec (like most other
video compression programs do), I guess there is a similar thing for other
platforms.
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On Mon, 25 Aug 2008 08:53:55 +0200, "scott" <sco### [at] scott com> wrote:
>For Windows (and other OSs I guess)
Thanks Scot, you have made me rethink what I meant :)
What I really want is a good codec that almost everyone will have on their
machines. So that I can post small animations here without complaints that the
file cannot be opened. I know that I'm not asking much ;) This is too "on topic"
for this group, I think.
Having said that I realise that I've not posted in p.b.a for ages as most of my
files are too large to be accepted.
Again thanks.
--
Regards
Stephen
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From: scott
Subject: Re: Subject: Stupid Windows Movie Maker (and TMPGEnc) question
Date: 25 Aug 2008 06:56:16
Message: <48b28fd0$1@news.povray.org>
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> Having said that I realise that I've not posted in p.b.a for ages as most
> of my
> files are too large to be accepted.
You can always upload to a website like YouTube and post the link, the
latest "high quality" setting on YouTube doesn't seem to be that bad. IMO a
much better option than crippling your POV work down to 700KB with an old
codec to ensure compatibility.
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