[MEncoder-users] (work-in-progress) XviD encoding guide

[Dominik 'Rathann' Mierzejewski]

On Tuesday, 21 June 2005 at 15:54, Guillaume POIRIER wrote:
> Hello,
> 
> Here's a work-in-progress encoding guide for XviD MPEG4-ASP codec that
> should one day make its way to our documentation.
> As the world of video encoding is one of those areas where using this
> or that set of options is often a matter of choice, I'd like to hear
> what you may have to say about that document.
> 
> It still lacks some option, and says almost nothing about the PSNR
> (in/de)crease to expect from using each option. If you have those
> figures on hand, please feel free to send them to me.
> 
> It also lack encoding examples, and information about custom
> quantization matrices, though it seems to me this subject is too
> controversial to get engraved in stone in an official documentation.
> 
> All feedbacks are welcome, either technical, or about my louzy English

"lousy" ;)

> that you wish to improve.
> 
> Regards,
> Guillaume
> 
> ------------------------
> <sect1 id="menc-feat-xvid">
> <title>Encoding with the <systemitem class="library">XviD</systemitem>
> codec</title>
> <para>
>   <systemitem class="library">XviD</systemitem> is a free library for
>   encoding MPEG-4 ASP video streams.
>   Before starting to encode, you need to <link linkend="xvid">
>   set up <application>MEncoder</application> to support it</link>.
> </para>
> <para>
>   This guide mainly aims at featuring the same kind of information
>   as x264's encoding guide.
>   Therefore, please begin by reading
>   <link linkend="menc-feat-x264-intro">the first part</link> of that
>   guide.
> </para>
> 
> <sect2 id="menc-feat-xvid-intro">
> <title>What options should I use to get the best results?</title>
> 
> <para>
>   Please begin by reviewing the
>   <systemitem class="library">XviD</systemitem> section of
>   <application>MPlayer</application>'s man page.
>   This section is intended to be a supplement to the man page.
> </para>
> <para>
>   The XviD's default settings are already a good trade off speed vs.

"tradeoff/trade-off between speed and ..."

>   quality, therefore, if you can safely stick to them if the

scratch the ", if"

>   following section puzzles you.
> </para>
> </sect2>
> 
> <sect2 id="menc-feat-xvid-encoding-options">
> <title>Encoding options of <systemitem class="library">XviD</systemitem></title>
> 
> <itemizedlist>
> 
> <listitem><para>
>   <emphasis role="bold">vhq</emphasis>
>     Default setting may safely be used on every encode, when higher

"... may be safely used for/during every encode, while higher..."

>     settings always help quality, but are significantly slower.
>     Turning it off will noticeably speed-up encode if you need speed.

"... speed-up encoding..."

> </para></listitem>
> 
> <listitem><para>
>   <emphasis role="bold">bvhq</emphasis>
>     This does the same job as vhq, but does it on B-frames.
>     It has a negligible impact on speed, and slightly improves quality
>     (around +0.1dB PSNR).
> </para></listitem>
> 
> <listitem><para>
>   <emphasis role="bold">max_bframes</emphasis>
>     A higher number of consecutive allowed B-frames usually improves
>     compressibility while this may lead to more blocking artifacts.
>     Default setting is a good trade-off of compressability vs. quality,

"trade-off between compress_i_bility and quality"

>     but you may increase it up to 3 if you're bitrate-shorted, while
>     you may also decrease it to 1 or 0 if you're aiming at perfect

"short on bitrate/bitrate-starved. You may also decrease it..."

>     quality though this might waste more bits than the increased of
>     subjective quality is worth.

Either "increase of quality" or "increased quality". Either way, the whole
sentence sounds awkward.

> </para></listitem>
> <listitem><para>
>   <emphasis role="bold">bf_threshold</emphasis>
>     This controls the B-frame sensibility of the encoder, where a higher
>     value leads to more b-frames being used (and vice versa).
>     This setting is to be used together with <option>max_bframes</option>,
>     so that if you are bitrate-shorted, you should increase both

"so if you are short on bitrate/bitrate-starved"

>     <option>max_bframes</option> and <option>bf_threshold</option>,
>     while you may <option>max_bframes</option> and reduce

while you may... what?

>     <option>bf_threshold</option> so that the encoder may use more
>     B-frames in places that only really need them.
>     A low number of <option>max_bframes</option> and a high value of
>     <option>bf_threshold</option> is probably not a wise choice as it
>     will force the encoder to put B-frames in places that would not
>     benefit from them, therefore reducing visual quality.
>     However, if you need to be compatible with standalone players that
>     only supports DivX profiles (which only supports up to 1 consecutive
>     B-frame), this would be you only possibility to increase
>     compressibility through using B-frames.
> </para></listitem>
> 
> <listitem><para>
>   <emphasis role="bold">trellis</emphasis>
>     Optimizes the motion estimation and allows significant bit saving
>     which would be spent elsewhere on the video, raising overall visual
>     quality.
>     You can safely leave it on as its impact on quality is very sensible,
>     but if you're looking for speed, only disable it if you have turn

turned

Not too bad, otherwise. ;)
I'm sure The Wanderer will find more than I did.

Regards,
R.

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