menc-feat-xvid.html

MPlayer-mingw32-1.0rc2.zip 经典播放器源码

  This setting is to control the precision of the motion estimation.
  The higher <tt class="option">me_quality</tt>, the more
  precise the estimation of the original motion will be, and the
  better the resulting clip will capture the original motion.
  </p><p>
  The default setting is best in all cases;
  thus it is not recommended to turn it down unless you are
  really looking for speed, as all the bits saved by a good motion
  estimation would be spent elsewhere, raising overall quality.
  Therefore, do not go any lower than 5, and even that only as a last
  resort.
  </p></li><li><p>
  <span class="bold"><strong>chroma_me</strong></span>
  Improves motion estimation by also taking the chroma (color)
  information into account, whereas <tt class="option">me_quality</tt>
  alone only uses luma (grayscale).
  This slows down encoding by 5-10% but improves visual quality
  quite a bit by reducing blocking effects and reduces filesize by
  around 1.3%.
  If you are looking for speed, you should disable this option before
  starting to consider reducing <tt class="option">me_quality</tt>.
</p></li><li><p>
  <span class="bold"><strong>chroma_opt</strong></span>
  Is intended to increase chroma image quality around pure
  white/black edges, rather than improving compression.
  This can help to reduce the "red stairs" effect.
</p></li><li><p>
  <span class="bold"><strong>lumi_mask</strong></span>
  Tries to give less bitrate to part of the picture that the
  human eye cannot see very well, which should allow the encoder
  to spend the saved bits on more important parts of the picture.
  The quality of the encode yielded by this option highly depends
  on personal preferences and on the type and monitor settings
  used to watch it (typically, it will not look as good if it is
  bright or if it is a TFT monitor).
</p></li><li><p>
  <span class="bold"><strong>qpel</strong></span>
  Raise the number of candidate motion vectors by increasing
  the precision of the motion estimation from halfpel to
  quarterpel.
  The idea is to find better motion vectors which will in return
  reduce bitrate (hence increasing quality).
  However, motion vectors with quarterpel precision require a
  few extra bits to code, but the candidate vectors do not always
  give (much) better results.
  Quite often, the codec still spends bits on the extra precision,
  but little or no extra quality is gained in return.
  Unfortunately, there is no way to foresee the possible gains of
  <tt class="option">qpel</tt>, so you need to actually encode with and
  without it to know for sure.
  </p><p>
  <tt class="option">qpel</tt> can be almost double encoding time, and
  requires as much as 25% more processing power to decode.
  It is not supported by all standalone players.
  </p></li><li><p>
  <span class="bold"><strong>gmc</strong></span>
  Tries to save bits on panning scenes by using a single motion
  vector for the whole frame.
  This almost always raises PSNR, but significantly slows down
  encoding (as well as decoding).
  Therefore, you should only use it when you have turned
  <tt class="option">vhq</tt> to the maximum.
  <code class="systemitem">Xvid</code>'s GMC is more
  sophisticated than DivX's, but is only supported by few
  standalone players.
</p></li></ul></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="menc-feat-xvid-encoding-profiles"></a>14.4.3.聽Encoding profiles</h3></div></div></div><p>
Xvid supports encoding profiles through the <tt class="option">profile</tt> option,
which are used to impose restrictions on the properties of the Xvid video
stream such that it will be playable on anything which supports the
chosen profile.
The restrictions relate to resolutions, bitrates and certain MPEG-4
features.
The following table shows what each profile supports.
</p><div class="informaltable"><table border="1"><colgroup><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"><col align="center"></colgroup><tbody><tr><td align="center">聽</td><td colspan="4" align="center">Simple</td><td colspan="6" align="center">Advanced Simple</td><td colspan="6" align="center">DivX</td></tr><tr><td align="center">Profile name</td><td align="center">0</td><td align="center">1</td><td align="center">2</td><td align="center">3</td><td align="center">0</td><td align="center">1</td><td align="center">2</td><td align="center">3</td><td align="center">4</td><td align="center">5</td><td align="center">Handheld</td><td align="center">Portable NTSC</td><td align="center">Portable PAL</td><td align="center">Home Theater NTSC</td><td align="center">Home Theater PAL</td><td align="center">HDTV</td></tr><tr><td align="center">Width [pixels]</td><td align="center">176</td><td align="center">176</td><td align="center">352</td><td align="center">352</td><td align="center">176</td><td align="center">176</td><td align="center">352</td><td align="center">352</td><td align="center">352</td><td align="center">720</td><td align="center">176</td><td align="center">352</td><td align="center">352</td><td align="center">720</td><td align="center">720</td><td align="center">1280</td></tr><tr><td align="center">Height [pixels]</td><td align="center">144</td><td align="center">144</td><td align="center">288</td><td align="center">288</td><td align="center">144</td><td align="center">144</td><td align="center">288</td><td align="center">288</td><td align="center">576</td><td align="center">576</td><td align="center">144</td><td align="center">240</td><td align="center">288</td><td align="center">480</td><td align="center">576</td><td align="center">720</td></tr><tr><td align="center">Frame rate [fps]</td><td align="center">15</td><td align="center">15</td><td align="center">15</td><td align="center">15</td><td align="center">30</td><td align="center">30</td><td align="center">15</td><td align="center">30</td><td align="center">30</td><td align="center">30</td><td align="center">15</td><td align="center">30</td><td align="center">25</td><td align="center">30</td><td align="center">25</td><td align="center">30</td></tr><tr><td align="center">Max average bitrate [kbps]</td><td align="center">64</td><td align="center">64</td><td align="center">128</td><td align="center">384</td><td align="center">128</td><td align="center">128</td><td align="center">384</td><td align="center">768</td><td align="center">3000</td><td align="center">8000</td><td align="center">537.6</td><td align="center">4854</td><td align="center">4854</td><td align="center">4854</td><td align="center">4854</td><td align="center">9708.4</td></tr><tr><td align="center">Peak average bitrate over 3 secs [kbps]</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">800</td><td align="center">8000</td><td align="center">8000</td><td align="center">8000</td><td align="center">8000</td><td align="center">16000</td></tr><tr><td align="center">Max. B-frames</td><td align="center">0</td><td align="center">0</td><td align="center">0</td><td align="center">0</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">0</td><td align="center">1</td><td align="center">1</td><td align="center">1</td><td align="center">1</td><td align="center">2</td></tr><tr><td align="center">MPEG quantization</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td></tr><tr><td align="center">Adaptive quantization</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td></tr><tr><td align="center">Interlaced encoding</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td></tr><tr><td align="center">Quaterpixel</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td></tr><tr><td align="center">Global motion compensation</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">X</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td><td align="center">聽</td></tr></tbody></table></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="menc-feat-xvid-example-settings"></a>14.4.4.聽Encoding setting examples</h3></div></div></div><p>
The following settings are examples of different encoding
option combinations that affect the speed vs quality tradeoff
at the same target bitrate.
</p><p>
All the encoding settings were tested on a 720x448 @30000/1001 fps
video sample, the target bitrate was 900kbps, and the machine was an
AMD-64 3400+ at 2400 MHz in 64 bits mode.
Each encoding setting features the measured encoding speed (in
frames per second) and the PSNR loss (in dB) compared to the "very
high quality" setting.
Please understand that depending on your source, your machine type
and development advancements, you may get very different results.
</p><div class="informaltable"><table border="1"><colgroup><col><col><col><col></colgroup><thead><tr><th>Description</th><th>Encoding options</th><th>speed (in fps)</th><th>Relative PSNR loss (in dB)</th></tr></thead><tbody><tr><td>Very high quality</td><td><tt class="option">chroma_opt:vhq=4:bvhq=1:quant_type=mpeg</tt></td><td>16fps</td><td>0dB</td></tr><tr><td>High quality</td><td><tt class="option">vhq=2:bvhq=1:chroma_opt:quant_type=mpeg</tt></td><td>18fps</td><td>-0.1dB</td></tr><tr><td>Fast</td><td><tt class="option">turbo:vhq=0</tt></td><td>28fps</td><td>-0.69dB</td></tr><tr><td>Realtime</td><td><tt class="option">turbo:nochroma_me:notrellis:max_bframes=0:vhq=0</tt></td><td>38fps</td><td>-1.48dB</td></tr></tbody></table></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="menc-feat-enc-libavcodec.html">Prev</a>聽</td><td width="20%" align="center"><a accesskey="u" href="encoding-guide.html">Up</a></td><td width="40%" align="right">聽<a accesskey="n" href="menc-feat-x264.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">14.3.聽Encoding with the <code class="systemitem">libavcodec</code>
  codec family聽</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">聽14.5.聽Encoding with the
  <code class="systemitem">x264</code> codec</td></tr></table></div></body></html>