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<div class="section" id="preset-options">
<h1>Preset Options<a class="headerlink" href="#preset-options" title="Permalink to this headline">¶</a></h1>
<div class="section" id="presets">
<span id="id1"></span><h2>Presets<a class="headerlink" href="#presets" title="Permalink to this headline">¶</a></h2>
<p>x265 has ten predefined <a class="reference internal" href="cli.html#cmdoption--preset"><code class="xref std std-option docutils literal"><span class="pre">--preset</span></code></a> options that optimize the
trade-off between encoding speed (encoded frames per second) and
compression efficiency (quality per bit in the bitstream). The default
preset is medium. It does a reasonably good job of finding the best
possible quality without spending excessive CPU cycles looking for the
absolute most efficient way to achieve that quality. When you use
faster presets, the encoder takes shortcuts to improve performance at
the expense of quality and compression efficiency. When you use slower
presets, x265 tests more encoding options, using more computations to
achieve the best quality at your selected bit rate (or in the case of
–crf rate control, the lowest bit rate at the selected quality).</p>
<p>The presets adjust encoder parameters as shown in the following table.
Any parameters below that are specified in your command-line will be
changed from the value specified by the preset.</p>
<table border="1" class="docutils">
<colgroup>
<col width="18%" />
<col width="11%" />
<col width="11%" />
<col width="10%" />
<col width="7%" />
<col width="5%" />
<col width="7%" />
<col width="5%" />
<col width="7%" />
<col width="10%" />
<col width="9%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head"> </th>
<th class="head">ultrafast</th>
<th class="head">superfast</th>
<th class="head">veryfast</th>
<th class="head">faster</th>
<th class="head">fast</th>
<th class="head">medium</th>
<th class="head">slow</th>
<th class="head">slower</th>
<th class="head">veryslow</th>
<th class="head">placebo</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>ctu</td>
<td>32</td>
<td>32</td>
<td>64</td>
<td>64</td>
<td>64</td>
<td>64</td>
<td>64</td>
<td>64</td>
<td>64</td>
<td>64</td>
</tr>
<tr class="row-odd"><td>min-cu-size</td>
<td>16</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
</tr>
<tr class="row-even"><td>bframes</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>4</td>
<td>4</td>
<td>4</td>
<td>4</td>
<td>8</td>
<td>8</td>
<td>8</td>
</tr>
<tr class="row-odd"><td>b-adapt</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
</tr>
<tr class="row-even"><td>rc-lookahead</td>
<td>5</td>
<td>10</td>
<td>15</td>
<td>15</td>
<td>15</td>
<td>20</td>
<td>25</td>
<td>30</td>
<td>40</td>
<td>60</td>
</tr>
<tr class="row-odd"><td>lookahead-slices</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>8</td>
<td>4</td>
<td>4</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>scenecut</td>
<td>0</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
<td>40</td>
</tr>
<tr class="row-odd"><td>ref</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>4</td>
<td>5</td>
<td>5</td>
</tr>
<tr class="row-even"><td>limit-refs</td>
<td>0</td>
<td>0</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>2</td>
<td>1</td>
<td>0</td>
</tr>
<tr class="row-odd"><td>me</td>
<td>dia</td>
<td>hex</td>
<td>hex</td>
<td>hex</td>
<td>hex</td>
<td>hex</td>
<td>star</td>
<td>star</td>
<td>star</td>
<td>star</td>
</tr>
<tr class="row-even"><td>merange</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>57</td>
<td>92</td>
</tr>
<tr class="row-odd"><td>subme</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>5</td>
</tr>
<tr class="row-even"><td>rect</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-odd"><td>amp</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>limit-modes</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>0</td>
</tr>
<tr class="row-odd"><td>max-merge</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>5</td>
</tr>
<tr class="row-even"><td>early-skip</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
</tr>
<tr class="row-odd"><td>fast-intra</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
</tr>
<tr class="row-even"><td>b-intra</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-odd"><td>sao</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>signhide</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-odd"><td>weightp</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>weightb</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-odd"><td>aq-mode</td>
<td>0</td>
<td>0</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-even"><td>cuTree</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="row-odd"><td>rdLevel</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>4</td>
<td>6</td>
<td>6</td>
<td>6</td>
</tr>
<tr class="row-even"><td>rdoq-level</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>0</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
</tr>
<tr class="row-odd"><td>tu-intra</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>3</td>
<td>4</td>
</tr>
<tr class="row-even"><td>tu-inter</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>3</td>
<td>4</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="tuning">
<span id="tunings"></span><h2>Tuning<a class="headerlink" href="#tuning" title="Permalink to this headline">¶</a></h2>
<p>There are a few <a class="reference internal" href="cli.html#cmdoption--tune"><code class="xref std std-option docutils literal"><span class="pre">--tune</span></code></a> options available, which are applied
after the preset.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <em>psnr</em> and <em>ssim</em> tune options disable all optimizations that
sacrafice metric scores for perceived visual quality (also known as
psycho-visual optimizations). By default x265 always tunes for
highest perceived visual quality but if one intends to measure an
encode using PSNR or SSIM for the purpose of benchmarking, we highly
recommend you configure x265 to tune for that particular metric.</p>
</div>
<table border="1" class="docutils">
<colgroup>
<col width="21%" />
<col width="79%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">–tune</th>
<th class="head">effect</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>psnr</td>
<td>disables adaptive quant, psy-rd, and cutree</td>
</tr>
<tr class="row-odd"><td>ssim</td>
<td>enables adaptive quant auto-mode, disables psy-rd</td>
</tr>
<tr class="row-even"><td>grain</td>
<td>improves retention of film grain. more below</td>
</tr>
<tr class="row-odd"><td>fastdecode</td>
<td>no loop filters, no weighted pred, no intra in B</td>
</tr>
<tr class="row-even"><td>zerolatency</td>
<td>no lookahead, no B frames, no cutree</td>
</tr>
</tbody>
</table>
<div class="section" id="film-grain-retention">
<h3>Film Grain Retention<a class="headerlink" href="#film-grain-retention" title="Permalink to this headline">¶</a></h3>
<p><a class="reference internal" href="cli.html#cmdoption--tune"><code class="xref std std-option docutils literal"><span class="pre">--tune</span></code></a> <em>grain</em> tries to improve the retention of film grain in
the reconstructed output. It disables rate distortion optimizations in
quantization, and increases the default psy-rd.</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--psy-rd"><code class="xref std std-option docutils literal"><span class="pre">--psy-rd</span></code></a> 0.5</li>
<li><a class="reference internal" href="cli.html#cmdoption--rdoq-level"><code class="xref std std-option docutils literal"><span class="pre">--rdoq-level</span></code></a> 0</li>
<li><a class="reference internal" href="cli.html#cmdoption--psy-rdoq"><code class="xref std std-option docutils literal"><span class="pre">--psy-rdoq</span></code></a> 0</li>
</ul>
</div></blockquote>
<p>It lowers the strength of adaptive quantization, so residual energy can
be more evenly distributed across the (noisy) picture:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--aq-strength"><code class="xref std std-option docutils literal"><span class="pre">--aq-strength</span></code></a> 0.3</li>
</ul>
</div></blockquote>
<p>And it similarly tunes rate control to prevent the slice QP from
swinging too wildly from frame to frame:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--ipratio"><code class="xref std std-option docutils literal"><span class="pre">--ipratio</span></code></a> 1.1</li>
<li><a class="reference internal" href="cli.html#cmdoption--pbratio"><code class="xref std std-option docutils literal"><span class="pre">--pbratio</span></code></a> 1.1</li>
<li><a class="reference internal" href="cli.html#cmdoption--qcomp"><code class="xref std std-option docutils literal"><span class="pre">--qcomp</span></code></a> 0.8</li>
</ul>
</div></blockquote>
<p>And lastly it reduces the strength of deblocking to prevent grain being
blurred on block boundaries:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--deblock"><code class="xref std std-option docutils literal"><span class="pre">--deblock</span></code></a> -2</li>
</ul>
</div></blockquote>
</div>
<div class="section" id="fast-decode">
<h3>Fast Decode<a class="headerlink" href="#fast-decode" title="Permalink to this headline">¶</a></h3>
<p><a class="reference internal" href="cli.html#cmdoption--tune"><code class="xref std std-option docutils literal"><span class="pre">--tune</span></code></a> <em>fastdecode</em> disables encoder features which tend to be
bottlenecks for the decoder. It is intended for use with 4K content at
high bitrates which can cause decoders to struggle. It disables both
HEVC loop filters, which tend to be process bottlenecks:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--no-deblock"><code class="xref std std-option docutils literal"><span class="pre">--no-deblock</span></code></a></li>
<li><a class="reference internal" href="cli.html#cmdoption--no-sao"><code class="xref std std-option docutils literal"><span class="pre">--no-sao</span></code></a></li>
</ul>
</div></blockquote>
<p>It disables weighted prediction, which tend to be bandwidth bottlenecks:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--no-weightp"><code class="xref std std-option docutils literal"><span class="pre">--no-weightp</span></code></a></li>
<li><a class="reference internal" href="cli.html#cmdoption--no-weightb"><code class="xref std std-option docutils literal"><span class="pre">--no-weightb</span></code></a></li>
</ul>
</div></blockquote>
<p>And it disables intra blocks in B frames with <a class="reference internal" href="cli.html#cmdoption--no-b-intra"><code class="xref std std-option docutils literal"><span class="pre">--no-b-intra</span></code></a>
since intra predicted blocks cause serial dependencies in the decoder.</p>
</div>
<div class="section" id="zero-latency">
<h3>Zero Latency<a class="headerlink" href="#zero-latency" title="Permalink to this headline">¶</a></h3>
<p>There are two halves to the latency problem. There is latency at the
decoder and latency at the encoder. <a class="reference internal" href="cli.html#cmdoption--tune"><code class="xref std std-option docutils literal"><span class="pre">--tune</span></code></a> <em>zerolatency</em>
removes latency from both sides. The decoder latency is removed by:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--bframes"><code class="xref std std-option docutils literal"><span class="pre">--bframes</span></code></a> 0</li>
</ul>
</div></blockquote>
<p>Encoder latency is removed by:</p>
<blockquote>
<div><ul class="simple">
<li><a class="reference internal" href="cli.html#cmdoption--b-adapt"><code class="xref std std-option docutils literal"><span class="pre">--b-adapt</span></code></a> 0</li>
<li><a class="reference internal" href="cli.html#cmdoption--rc-lookahead"><code class="xref std std-option docutils literal"><span class="pre">--rc-lookahead</span></code></a> 0</li>
<li><a class="reference internal" href="cli.html#cmdoption--no-scenecut"><code class="xref std std-option docutils literal"><span class="pre">--no-scenecut</span></code></a></li>
<li><a class="reference internal" href="cli.html#cmdoption--no-cutree"><code class="xref std std-option docutils literal"><span class="pre">--no-cutree</span></code></a></li>
<li><a class="reference internal" href="cli.html#cmdoption--frame-threads"><code class="xref std std-option docutils literal"><span class="pre">--frame-threads</span></code></a> 1</li>
</ul>
</div></blockquote>
<p>With all of these settings x265_encoder_encode() will run synchronously,
the picture passed as pic_in will be encoded and returned as NALs. These
settings disable frame parallelism, which is an important component for
x265 performance. If you can tolerate any latency on the encoder, you
can increase performance by increasing the number of frame threads. Each
additional frame thread adds one frame of latency.</p>
</div>
</div>
</div>
</div>
</div>
</div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Preset Options</a><ul>
<li><a class="reference internal" href="#presets">Presets</a></li>
<li><a class="reference internal" href="#tuning">Tuning</a><ul>
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