+<a name="Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options"></a>
+<h3 class="subsection"><a href="ffmpeg.html#toc-Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options">10.1.4 Floating-Point-Only AC-3 Encoding Options</a></h3>
+
+<p>These options are only valid for the floating-point encoder and do not exist
+for the fixed-point encoder due to the corresponding features not being
+implemented in fixed-point.
+</p>
+<dl compact="compact">
+<dt> ‘<samp>-channel_coupling <var>boolean</var></samp>’</dt>
+<dd><p>Enables/Disables use of channel coupling, which is an optional AC-3 feature
+that increases quality by combining high frequency information from multiple
+channels into a single channel. The per-channel high frequency information is
+sent with less accuracy in both the frequency and time domains. This allows
+more bits to be used for lower frequencies while preserving enough information
+to reconstruct the high frequencies. This option is enabled by default for the
+floating-point encoder and should generally be left as enabled except for
+testing purposes or to increase encoding speed.
+</p><dl compact="compact">
+<dt> ‘<samp>-1</samp>’</dt>
+<dt> ‘<samp>auto</samp>’</dt>
+<dd><p>Selected by Encoder (default)
+</p></dd>
+<dt> ‘<samp>0</samp>’</dt>
+<dt> ‘<samp>off</samp>’</dt>
+<dd><p>Disable Channel Coupling
+</p></dd>
+<dt> ‘<samp>1</samp>’</dt>
+<dt> ‘<samp>on</samp>’</dt>
+<dd><p>Enable Channel Coupling
+</p></dd>
+</dl>
+
+</dd>
+<dt> ‘<samp>-cpl_start_band <var>number</var></samp>’</dt>
+<dd><p>Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a
+value higher than the bandwidth is used, it will be reduced to 1 less than the
+coupling end band. If <var>auto</var> is used, the start band will be determined by
+the encoder based on the bit rate, sample rate, and channel layout. This option
+has no effect if channel coupling is disabled.
+</p><dl compact="compact">
+<dt> ‘<samp>-1</samp>’</dt>
+<dt> ‘<samp>auto</samp>’</dt>
+<dd><p>Selected by Encoder (default)
+</p></dd>
+</dl>
+
+</dd>
+</dl>
+
+
+<a name="Video-Encoders"></a>
+<h1 class="chapter"><a href="ffmpeg.html#toc-Video-Encoders">11. Video Encoders</a></h1>
+
+<p>A description of some of the currently available video encoders
+follows.
+</p>
+<a name="libvpx"></a>
+<h2 class="section"><a href="ffmpeg.html#toc-libvpx">11.1 libvpx</a></h2>
+
+<p>VP8 format supported through libvpx.
+</p>
+<p>Requires the presence of the libvpx headers and library during configuration.
+You need to explicitly configure the build with <code>--enable-libvpx</code>.
+</p>
+<a name="Options-1"></a>
+<h3 class="subsection"><a href="ffmpeg.html#toc-Options-1">11.1.1 Options</a></h3>
+
+<p>Mapping from FFmpeg to libvpx options with conversion notes in parentheses.
+</p>
+<dl compact="compact">
+<dt> ‘<samp>threads</samp>’</dt>
+<dd><p>g_threads
+</p>
+</dd>
+<dt> ‘<samp>profile</samp>’</dt>
+<dd><p>g_profile
+</p>
+</dd>
+<dt> ‘<samp>vb</samp>’</dt>
+<dd><p>rc_target_bitrate
+</p>
+</dd>
+<dt> ‘<samp>g</samp>’</dt>
+<dd><p>kf_max_dist
+</p>
+</dd>
+<dt> ‘<samp>keyint_min</samp>’</dt>
+<dd><p>kf_min_dist
+</p>
+</dd>
+<dt> ‘<samp>qmin</samp>’</dt>
+<dd><p>rc_min_quantizer
+</p>
+</dd>
+<dt> ‘<samp>qmax</samp>’</dt>
+<dd><p>rc_max_quantizer
+</p>
+</dd>
+<dt> ‘<samp>bufsize, vb</samp>’</dt>
+<dd><p>rc_buf_sz
+<code>(bufsize * 1000 / vb)</code>
+</p>
+<p>rc_buf_optimal_sz
+<code>(bufsize * 1000 / vb * 5 / 6)</code>
+</p>
+</dd>
+<dt> ‘<samp>rc_init_occupancy, vb</samp>’</dt>
+<dd><p>rc_buf_initial_sz
+<code>(rc_init_occupancy * 1000 / vb)</code>
+</p>
+</dd>
+<dt> ‘<samp>rc_buffer_aggressivity</samp>’</dt>
+<dd><p>rc_undershoot_pct
+</p>
+</dd>
+<dt> ‘<samp>skip_threshold</samp>’</dt>
+<dd><p>rc_dropframe_thresh
+</p>
+</dd>
+<dt> ‘<samp>qcomp</samp>’</dt>
+<dd><p>rc_2pass_vbr_bias_pct
+</p>
+</dd>
+<dt> ‘<samp>maxrate, vb</samp>’</dt>
+<dd><p>rc_2pass_vbr_maxsection_pct
+<code>(maxrate * 100 / vb)</code>
+</p>
+</dd>
+<dt> ‘<samp>minrate, vb</samp>’</dt>
+<dd><p>rc_2pass_vbr_minsection_pct
+<code>(minrate * 100 / vb)</code>
+</p>
+</dd>
+<dt> ‘<samp>minrate, maxrate, vb</samp>’</dt>
+<dd><p><code>VPX_CBR</code>
+<code>(minrate == maxrate == vb)</code>
+</p>
+</dd>
+<dt> ‘<samp>crf</samp>’</dt>
+<dd><p><code>VPX_CQ</code>, <code>VP8E_SET_CQ_LEVEL</code>
+</p>
+</dd>
+<dt> ‘<samp>quality</samp>’</dt>
+<dd><dl compact="compact">
+<dt> ‘<samp><var>best</var></samp>’</dt>
+<dd><p><code>VPX_DL_BEST_QUALITY</code>
+</p></dd>
+<dt> ‘<samp><var>good</var></samp>’</dt>
+<dd><p><code>VPX_DL_GOOD_QUALITY</code>
+</p></dd>
+<dt> ‘<samp><var>realtime</var></samp>’</dt>
+<dd><p><code>VPX_DL_REALTIME</code>
+</p></dd>
+</dl>
+
+</dd>
+<dt> ‘<samp>speed</samp>’</dt>
+<dd><p><code>VP8E_SET_CPUUSED</code>
+</p>
+</dd>
+<dt> ‘<samp>nr</samp>’</dt>
+<dd><p><code>VP8E_SET_NOISE_SENSITIVITY</code>
+</p>
+</dd>
+<dt> ‘<samp>mb_threshold</samp>’</dt>
+<dd><p><code>VP8E_SET_STATIC_THRESHOLD</code>
+</p>
+</dd>
+<dt> ‘<samp>slices</samp>’</dt>
+<dd><p><code>VP8E_SET_TOKEN_PARTITIONS</code>
+</p>
+</dd>
+<dt> ‘<samp>Alternate reference frame related</samp>’</dt>
+<dd><dl compact="compact">
+<dt> ‘<samp>vp8flags altref</samp>’</dt>
+<dd><p><code>VP8E_SET_ENABLEAUTOALTREF</code>
+</p></dd>
+<dt> ‘<samp><var>arnr_max_frames</var></samp>’</dt>
+<dd><p><code>VP8E_SET_ARNR_MAXFRAMES</code>
+</p></dd>
+<dt> ‘<samp><var>arnr_type</var></samp>’</dt>
+<dd><p><code>VP8E_SET_ARNR_TYPE</code>
+</p></dd>
+<dt> ‘<samp><var>arnr_strength</var></samp>’</dt>
+<dd><p><code>VP8E_SET_ARNR_STRENGTH</code>
+</p></dd>
+<dt> ‘<samp><var>rc_lookahead</var></samp>’</dt>
+<dd><p>g_lag_in_frames
+</p></dd>
+</dl>
+
+</dd>
+<dt> ‘<samp>vp8flags error_resilient</samp>’</dt>
+<dd><p>g_error_resilient
+</p>
+</dd>
+</dl>
+
+<p>For more information about libvpx see:
+<a href="http://www.webmproject.org/">http://www.webmproject.org/</a>
+</p>
+<a name="libx264"></a>
+<h2 class="section"><a href="ffmpeg.html#toc-libx264">11.2 libx264</a></h2>
+
+<p>H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 format supported through
+libx264.
+</p>
+<p>Requires the presence of the libx264 headers and library during
+configuration. You need to explicitly configure the build with
+<code>--enable-libx264</code>.
+</p>
+<a name="Options-2"></a>
+<h3 class="subsection"><a href="ffmpeg.html#toc-Options-2">11.2.1 Options</a></h3>
+
+<dl compact="compact">
+<dt> ‘<samp>preset <var>preset_name</var></samp>’</dt>
+<dd><p>Set the encoding preset.
+</p>
+</dd>
+<dt> ‘<samp>tune <var>tune_name</var></samp>’</dt>
+<dd><p>Tune the encoding params.
+Deprecated in favor of <var>x264_opts</var>
+</p>
+</dd>
+<dt> ‘<samp>fastfirstpass <var>bool</var></samp>’</dt>
+<dd><p>Use fast settings when encoding first pass, default value is 1.
+Deprecated in favor of <var>x264_opts</var>.
+</p>
+</dd>
+<dt> ‘<samp>profile <var>profile_name</var></samp>’</dt>
+<dd><p>Set profile restrictions.
+Deprecated in favor of <var>x264_opts</var>.
+</p>
+</dd>
+<dt> ‘<samp>level <var>level</var></samp>’</dt>
+<dd><p>Specify level (as defined by Annex A).
+Deprecated in favor of <var>x264_opts</var>.
+</p>
+</dd>
+<dt> ‘<samp>passlogfile <var>filename</var></samp>’</dt>
+<dd><p>Specify filename for 2 pass stats.
+Deprecated in favor of <var>x264_opts</var>.
+</p>
+</dd>
+<dt> ‘<samp>wpredp <var>wpred_type</var></samp>’</dt>
+<dd><p>Specify Weighted prediction for P-frames.
+Deprecated in favor of <var>x264_opts</var>.
+</p>
+</dd>
+<dt> ‘<samp>x264opts <var>options</var></samp>’</dt>
+<dd><p>Allow to set any x264 option, see x264 manual for a list.
+</p>
+<p><var>options</var> is a list of <var>key</var>=<var>value</var> couples separated by
+":".
+</p></dd>
+</dl>
+
+<p>For example to specify libx264 encoding options with ‘<tt>ffmpeg</tt>’:
+</p><table><tr><td> </td><td><pre class="example">ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
+</pre></td></tr></table>
+
+<p>For more information about libx264 and the supported options see:
+<a href="http://www.videolan.org/developers/x264.html">http://www.videolan.org/developers/x264.html</a>
+</p>