x264 fast recompress

[gigah72]

i need sometimes to recompress a video that's a bit too big. exact filesize is not needed, just to save some gb of limited hdd-space.
for the moment i'm useing this, but is it possible to get it faster, with loseing much?

x264.exe --crf 20 --level 4 --keyint 24 --min-keyint 2 --mixed-refs --bframes 3 --weightb --subme 5 --partitions i4x4,i8x8 --8x8dct --ipratio 1.1 --pbratio 1.1 --vbv-bufsize 25000 --vbv-maxrate 25000 --qcomp 0.5 --merange 12 --threads auto --progress --no-psnr --mvrange 511 --aud --output "C:\_vd\tmp\video.264" "C:\_vd\tmp\video.avs"

[Blue_MiSfit]

I wouldn't adjust keyint, ipratio, bpratio, qcomp, VBV etc... if you don't really know what you're doing.

If you're just trying to save some space and playback on the PC, you can safely remove a lot of your restrictions, and get it down to something like this:

--crf 20 --bframes 3 --b-adapt 2 --subme 9 --refs 4 --mixed-refs --8x8dct --threads auto --thread-input


Okay, those aren't exactly FAST settings, but they're about all I'd ever use :)


--crf 20 --bframes 3 --subme 6 --8x8dct --refs 2 --mixed-refs --threads auto --thread-input


Would be a bit faster ;)

~MiSfit

[gigah72]

thanks Blue_MiSfit,
but this is the opposit of what i hoped to read :)
the encoded stuff is not ment for playback on pc, but blu-ray oder standalone decoder like WD HD TV or such, tv is 42-50" full hd plasma/lcd.

seems that i'm one of the rare ppl who don't want to wait ages for an encode to finish, i also believe that a 1080p encode with avg bitrates arround 15000 (this what i got for a reencode of batman - dark knight) with such low analyze settings somehow can't be such crap useing x264 ;)

maybe someone else has an idea how to speed things up a bit?

[Dark Shikari]

thanks Blue_MiSfit,
but this is the opposit of what i hoped to read :)
the encoded stuff is not ment for playback on pc, but blu-ray oder standalone decoder like WD HD TV or such, tv is 42-50" full hd plasma/lcd.

seems that i'm one of the rare ppl who don't want to wait ages for an encode to finish, i also believe that a 1080p encode with avg bitrates arround 15000 (this what i got for a reencode of batman - dark knight) with such low analyze settings somehow can't be such crap useing x264 ;)

maybe someone else has an idea how to speed things up a bit?Er, why not use BD Rebuilder for re-encoding your Blu-rays?

[gigah72]

thanks Dark Shikari,

but i wasn't looking for an app to do this or that, but how to speedup my cmdline. if none has a suggestion, i'll try myself what happens if i change settings.
in the thread for realtime 720p50 encoding are some settigs/ideas i'll try, too.

[7oby]

x264.exe --crf 20 --vbv-bufsize 25000 --vbv-maxrate 25000
And to quote Dark Shikari:
One-pass VBV quality is vastly inferior to twopass VBV.
[...]
Please stop recommending CRF with VBV.
http://forum.doom9.org/showthread.php?p=1244894#post1244894

I noticed the same when comparing results.

[gigah72]

thanks 7oby,

but this crf vbv stuff thing is not directly related to my question and this is confusing me.
i did some test and found what i wanted to know, i guess.

[neuron2]

i did some test and found what i wanted to know, i guess. The polite thing to do, since you've opened this thread to the world, is to tell us what you found.

[gigah72]

hello neuron2,

sorry, it was never ment to be impolite, but from the responses here, i just thought none gives a frak about this, all have quads&cuda ;)

x264.exe --crf 20 --level 4 --keyint 24 --min-keyint 2 --bframes 3 --filter -1:-1 --subme 4 --partitions i4x4,i8x8 --8x8dct --ipratio 1.1 --pbratio 1.1 --vbv-bufsize 25000 --vbv-maxrate 25000 --qcomp 0.5 --merange 12 --threads auto --progress --no-psnr --mvrange 511 --aud --output bla.264 bla.avs

i don't know if all switches matter.

if my understanding of how compression works isn't completly bs, my resulting file will just be "a little" bigger when with all features turned on, but not worse in quality, i hope so atleast.

p.s.
about crf vbv, is there a free tool that can check vbv violations?

[Dark Shikari]

about crf vbv, is there a free tool that can check vbv violations?x264 will warn about VBV violations.

The issue with CRF+VBV is the same as with 1-pass; quality is more likely to suffer as a result of VBV.

[audyovydeo]

i just thought none gives a frak about this, all have quads&cuda ;)



wrong. My own "fast" settings :

set fast=-r 1 -b 16 --me hex -m 1 -t 0 -A none --direct auto --b-pyramid -w

You'll notice I keep cabac. Also, on a tip from Dark Shikari I tried --me dia -m 3 (subme 1 seems to be held in very low esteem).

I might also add that I very rarely use these settings, mainly when I want to get an idea of the compressibility of some content I'm working on.

cheers
audyovydeo

[burfadel]

Yeah, if you cut the settings back to much you'll approach the quality of Apple's implementation :)

[audyovydeo]

Yeah, if you cut the settings back to much you'll approach the quality of Apple's implementation :)

'cept that Apple's H.264 is orders of magnitude slower, even at "fast" settings ;-)

cheers
a/v

[AnonCrow]

Bit of a bump but same topic from a different angle.

Fast recompress = use(|convert) motion vectors from (lossy) source video. Macroblock partitions copied over too as a result.

Double/halve vector lengths if doubling/halving target video resolution.
Any other change in resolution would require a few frames of lookahead for vectors to at least try and maintain quality.
Quality wise , it ought to provide similar motion vectors as (t)esa at a fraction of the speed of dia.

Would the end result still be comparable to even x264 'veryfast' preset , since using existing motion vectors would also somewhat limit IPB frame decision,
unless some more magic went into motion vector conversion.