[MEncoder-users] (work-in-progress) XviD encoding guide
Dominik 'Rathann' Mierzejewski
dominik at rangers.eu.org
Tue Jun 21 16:43:06 CEST 2005
On Tuesday, 21 June 2005 at 15:54, Guillaume POIRIER wrote:
> 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
> that you wish to improve.
> <sect1 id="menc-feat-xvid">
> <title>Encoding with the <systemitem class="library">XviD</systemitem>
> <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>.
> 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
> <sect2 id="menc-feat-xvid-intro">
> <title>What options should I use to get the best results?</title>
> 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.
> 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.
> <sect2 id="menc-feat-xvid-encoding-options">
> <title>Encoding options of <systemitem class="library">XviD</systemitem></title>
> <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..."
> <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).
> <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.
> <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.
> <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
> 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
Not too bad, otherwise. ;)
I'm sure The Wanderer will find more than I did.
MPlayer RPMs maintainer: http://rpm.greysector.net/mplayer/
"I am Grey. I stand between the candle and the star. We are Grey.
We stand between the darkness ... and the light."
-- Delenn in Grey Council in Babylon 5:"Babylon Squared"
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