[MEncoder-users] Terrible results with x264

[Grozdan]

On Thu, Dec 23, 2010 at 6:55 PM, belcampo <belcampo at zonnet.nl> wrote:
> Grozdan wrote:
>>
>> On Thu, Dec 23, 2010 at 2:13 PM, belcampo <belcampo at zonnet.nl> wrote:
>>>
>>> Joseph Miller wrote:
>>>>
>>>> On Wed, Dec 22, 2010 at 4:19 PM, Jason Cumiskey
>>>> <jason.cumiskey at gmail.com> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I have just started using x264 to encode my dvds.  I am going for
>>>>> quality, not speed.  I am basing my -x264encopts off of the
>>>>> recommendations from
>>>>> http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-x264.html
>>>>>
>>>>> Here are the commands I issue (I am using 2 pass encode):
>>>>> mencoder -dvd-device /dev/dvd1 dvd://1 -alang eng -aid 128 -oac mp3lame
>>>>> -lameopts cbr:br=128:vol=7 -vf
>>>>> pullup,softskip,crop=704:480:10:0,hqdn3d=2:1:2,harddup -ovc x264
>>>>> -x264encopts
>>>>>
>>>>>
>>>>> pass=1:bitrate=1400:subq=1:partitions=all:8x8dct:me=umh:frameref=1:bframes=3:b_pyramid=normal:weight_b:threads=auto
>>>>> -o movie.h264
>>>>>
>>>>> # Pass 2
>>>>> mencoder -dvd-device /dev/dvd1 dvd://1 -alang eng -aid 128 -oac mp3lame
>>>>> -lameopts cbr:br=128:vol=7 -vf
>>>>> pullup,softskip,crop=704:480:10:0,hqdn3d=2:1:2,harddup -ovc x264
>>>>> -x264encopts
>>>>>
>>>>>
>>>>> pass=2:bitrate=1400:subq=6:partitions=all:8x8dct:me=umh:frameref=6:bframes=3:b_pyramid=normal:weight_b:threads=auto
>>>>> -o movie.h264
>>>>>
>>>>>
>>>>> On pass 2, I change subq to 6 and frameref to 6 (as recommended in the
>>>>> docs link above to speed up 1st pass and have higher quality for 2nd
>>>>> pass).Can anyone see anything obviously wrong in my command chain?  The
>>>>> resulting video is heavily pixelated and mplayer shows a bitrate of
>>>>> 0kbps.
>>>>>
>>> FYI. multi-pass does NOT add any quality, it's only usefull when you have
>>> a
>>> hard-limit of size to obey. If you need to put the result on a
>>> cd/usb-stick/DVD or something like that, then you can get max-quality
>>> given
>>> a fixed size.
>>> If that is not the case use a qp=16-26 for very good to very acceptable
>>> quality. You can leave out the bitrate when you choose Quality instead of
>>> Size.
>>>>
>>>> My experience has been that the bitrate option either doesn't work
>>>> very well, or I don't know how to use it.  Use qp=20 or so and you'll
>>>> get good quality.  I have just started using the presets as well and
>>>> preset=placebo gives very nice results.  Something like
>>>> qp=20:preset=placebo:pass=1 then switching to pass=3 for 2nd encoding
>>>> gives nice results and decent filesize.  I'm assuming that
>>>> preset=[veryslow|slower|slow] would probably also give good results.
>>>>
>>>> -Joseph
>>>> _______________________________________________
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>>>> MEncoder-users at mplayerhq.hu
>>>> https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
>>>
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>>
>> Why are you both recommending qp? How many times do experienced
>> encoders and the devs themselves need to mention that qp should NOT be
>> used since it's "very dumb" compared to crf, which is the preferred
>> option?
>
> I would like to learn how dumb I am. My observations:
> qp gives the most 'constant' quality, less quality variations than crf
> qp encodes 'significantly' faster than crf.

Well, not to attack you or anything, but you're not very bright if you
couldn't get the sentence above where the "very dumb" appears...
Please re-read it again and think about whether it's about you or
whether it's about the mode itself... Wait, I'll answer it for you.

IT'S ABOUT THE MODE ITSELF..... the qp mode is very dumb which means
it can't do "intelligent" decisions on how much bitrate to allocate or
not thus wasting where you could have come around with (much) lesser
bitrate and couldn't see the difference if you compared the crf with
the qp encode! The "very dumb" has absolutely nothing to do with you
but apparently it was too hard to see.

And in the world of encoding, it's not only about "the most constant
quality". There's an equally important factor or you wouldn't be
encoding, unless if you want to shift formats for some reason. It's
also about size. Why would you allocate, say, 1000kbps if you could
have come around with 800 only on that specific frame and absolutely
couldn't see the difference between the two?

about the being faster, I just asked Jason (x264 main dev). The only
case where qp is faster than crf is if lookahead doesn't matter or
isn't necessary. So why would you disable lookahead which improves
quality just to gain a little bit of speed?

And finally, I'll repeat what Jason often mentions.... [quote] qp is
only there for testing purposes. crf is the preferred mode for
encoding if you go for constant quality. [/quote]

 Every knowledgeable self-respected encoder uses and recommends crf.
If you think you're smarter than the devs or code itself, you're free
to use whatever you believe (how unlikely it may be) provides better
quality or speed.

>>
>> Gee, people, stop giving bad advice or just keep quiet if you don't know
>> :)
>>
>> About multipass, I do not have any issues with it nor get pixelated
>> results
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>
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