Mencoder defaults may be wrong

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Mencoder defaults may be wrong

Postby en5ads » Tue Dec 29, 2009 11:25 pm

keyint=1:vqscale=1:vqmin=2 is the default, but according to the manual for mencoder,

vqscale=<0−31>
Constant quantizer / constant quality encoding (selects fixed quantizer mode). A lower value means better quality but larger files (default: −1). In case of snow codec, value 0 means lossless encoding. Since the other codecs do not support this, vqscale=0 will have an undefined effect. 1 is not recommended (see vqmin for details).

vqmin=<1−31>
minimum quantizer
1 Not recommended (much larger file, little quality difference and weird side effects: msmpeg4, h263 will be very low quality, ratecontrol will be confused resulting in lower quality and some decoders will not be able to decode it).
2 Recommended for normal mpeg4/mpeg1video encoding (default).
...

keyint=<0−300>
maximum interval between keyframes in frames (default: 250 or one keyframe every ten seconds in a 25fps movie. This is the recommended default for MPEG-4). Most codecs require regular keyframes in order to limit the accumulation of mismatch error. Keyframes are also needed for seeking, as seeking is only possible to a keyframe − but keyframes need more space than other frames, so larger numbers here mean slightly smaller files but less precise seeking. 0 is equivalent to 1, which makes every frame a keyframe. Values >300 are not recommended as the quality might be bad depending upon decoder, encoder and luck. It is common for MPEG-1/2 to use values <=30.

This means the default is a keyframe for every frame, which is a bit odd. I got better quality, lower cpu decoding with
keyint=25:vqscale=2:vqmin=2

Anthony
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Re: Mencoder defaults may be wrong

Postby ExSport » Tue Dec 29, 2009 11:59 pm

Code: Select all
keyint=1:vqscale=1:vqmin=2

Keyint can be up to 25 but then CPU usage is higher but bitrate lower. Keyint=1 is equivalent for best quality for lowest CPU usage when bitrate size is not problem.
Keyint=5 is best optimum.
vqscale=1 is/was not recommended because quality increase is not so high as bitrate so for encoding is not good because of its size.
But when you will not save it for storage but stream it on 1Gbit line to PS3, definitely it has better quality on HD videos(720p/1080p) where every bit is visible. Also this documentation is quite old so "undefined effect" was maybe in old versions of MEncoder but I suppose now it is more stable ;)
vqmin=1 has definitely side effects(on some videos with vqmin=1 buffer overflow is generated and video will freeze) so vqmin=2 is best optimum and also recommended.
So with good CPU and good line(100/1000Mbits) 5-1-2 or 1-1-2 is best optimum. Higher keyint, the better bitrate precision(lower bitrate/higher CPU load/no quality loss when no high values used)
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Re: Mencoder defaults may be wrong

Postby en5ads » Wed Dec 30, 2009 8:45 am

Well, decoding on XMBC definitely had some problems until I backed down the values. Perhaps it should be the best, but it wasn't.

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Re: Mencoder defaults may be wrong

Postby shagrath » Fri Jan 01, 2010 8:58 pm

en5ads wrote:This means the default is a keyframe for every frame, which is a bit odd. I got better quality, lower cpu decoding with
keyint=25:vqscale=2:vqmin=2


and slower encoding ? I know the values are wrong (especially the key frames) but that's not the point, the point was to be able to transcode 1080p videos on "average" computers (originally on my own actually :p)
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Re: Mencoder defaults may be wrong

Postby BigRed » Sun Jan 10, 2010 11:55 pm

I just tried the settings 5-1-2 because I wasn't satisfied with the results I got with 1-1-1.

I have an Intel dual core 3ghz, 4Gb ram (DDR2 - 1066 OC), asus ASUS P5QL-EM , Seagate ST 3500320AS as disk (500Mb, 32Mb cache), XP Pro, gigabit ethernet to the PS3.

My issue was that I got pixelization and sometimes the image started to be more and more fuzzier until it "reset" to a clear frame; after that, the process of "fuzzyfication" started again.

With the new settings I don't get the fuzzyfication anymore, I get a sharper image and more brilliant colors. I deselected also the "skips loop deblocking" but I don't know if that helped.

Hope that helps...
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Re: Mencoder defaults may be wrong

Postby DPT » Tue Mar 08, 2011 9:29 pm

Hmm sorry i dont understand this :(

Im using my ps3 media server most to see mkv files 1080p on a gigabit lan.

But i use 1-1-1 (Losseless quality)

But im getting some lag sometimes. Im on

AMD x4 955 3,20 Ghz
8 Gb Corsair Ram
1000 mbit lan (ps3 media server says 512 mbit)

What can you recormend?

Regards
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Re: Mencoder defaults may be wrong

Postby Coltaine79 » Wed Mar 09, 2011 5:03 am

I've been using 5-1-2 for the past 8 months and when I do a casual "does it look good test" it certainly passes ;)
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Re: Mencoder defaults may be wrong

Postby DPT » Wed Mar 09, 2011 9:29 am

Okay thanks.

It is just becaurse i want the BEST quality :)
So what options shall i use?
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Re: Mencoder defaults may be wrong

Postby meskibob » Wed Mar 09, 2011 2:15 pm

DPT wrote:Okay thanks.

It is just becaurse i want the BEST quality :)
So what options shall i use?

ExSport states it pretty clearly...
ExSport wrote:So with good CPU and good line(100/1000Mbits) 5-1-2 or 1-1-2 is best optimum. Higher keyint, the better bitrate precision(lower bitrate/higher CPU load/no quality loss when no high values used)
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Re: Mencoder defaults may be wrong

Postby DPT » Wed Mar 09, 2011 8:30 pm

So what is the diffrent between 5-1-2 or 1-1-2 ?

So 1-1-1 is not the best?

Regards DPT
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