[MEncoder-users] Different versions, very different results

[Grozdan]

2009/7/25 Christian Ebert <blacktrash at gmx.net>:
> * Grozdan on Saturday, July 25, 2009 at 11:01:36 +0200
>> 2009/7/25 Matyas <mplayer.list at sustik.com>:
>>> While testing encoding settings I noticed that I get quite different results
>>> with different levels of mencoder.
>>>
>>> 1. The current SVN fails in the second pass with:
>>>  x264 [error]: bad frame number ...
>>>
>>> 2. Version r28850 determines a bitrate of 734 kb/s in the first pass.
>>>
>>> 3. Version r29108 determines a bitrate of 647 kb/s in the first pass.
>>>
>>> All the same parms.
>>>
>>> Was there a vast improvement in compression efficiency from r28850 to
>>> r29108?
>>
>> Compression efficiency has nothing to do with mencoder when you're
>> using H.264. It depends on the libx264 library which mencoder uses. A
>> few days ago, the x264 devs added a new VAQ which in many cases lowers
>> the bitrate of the encoding and in some cases increases it. It is not
>> enabled by default but if you used aq_mode=2  that may explain why you
>> get such different bitrate results. Of course, assuming you're using
>> the x264 revision which offers aq_mode=2
>
> Ah, thanks for pointing to this new parameter. From mediainfo I
> get that aq_mode=1 is the default (outputs aq=1:1.00 when I set
> neither aq_mode nor aq_strength). Shouldn't that be 0 from what
> you're saying? Also the manpage is misleading:

No, AQ is enabled by default and is set to 1 (old-AQ). If you want to
disable it (which I don't really recommend except in special cases),
you must explicitly do so by setting aq_mode=0. If you want to use the
*new* AQ, then again you must explicitly tell x264 by enabling it with
aq_mode=2

>
>       aq_mode=<0-2>
>              Defines how adaptive quantization (AQ) distributes bits:
>                 0    disabled
>                 1    Avoid moving bits between frames.
>                 2    Move bits between frames (by default).
>
> From this I would gather that 2 is the default.
>
> Which is it now ;-)

man page is outdated and incorrect

>
> c
> --
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