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<h1>Postprocessing Decoder</h1>

This example adds postprocessing to the simple decoder loop.

<h2>Initializing Postprocessing</h2>

You must inform the codec that you might request postprocessing at
initialization time. This is done by passing the VPX_CODEC_USE_POSTPROC
flag to <code>vpx_codec_dec_init</code>. If the codec does not support
postprocessing, this call will return VPX_CODEC_INCAPABLE. For
demonstration purposes, we also fall back to default initialization if
the codec does not provide support.

<pre class="c">/* Initialize codec */
res = vpx_codec_dec_init&#40;&amp;codec, interface, NULL,
 VPX_CODEC_USE_POSTPROC&#41;;
if&#40;res == VPX_CODEC_INCAPABLE&#41; &#123;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;NOTICE: Postproc not supported by %s\n&quot;,
 vpx_codec_iface_name&#40;interface&#41;&#41;;
 res = vpx_codec_dec_init&#40;&amp;codec, interface, NULL, flags&#41;;
&#125;
if&#40;res&#41;
 die_codec&#40;&amp;codec, &quot;Failed to initialize decoder&quot;&#41;;</pre>

<h2>Using Adaptive Postprocessing</h2>

VP6 provides &#8220;adaptive postprocessing.&#8221; It will automatically select the
best postprocessing filter on a frame by frame basis based on the amount
of time remaining before the user&#8217;s specified deadline expires. The
special value 0 indicates that the codec should take as long as
necessary to provide the best quality frame. This example gives the
codec 15ms (15000us) to return a frame. Remember that this is a soft
deadline, and the codec may exceed it doing its regular processing. In
these cases, no additional postprocessing will be done.

<pre class="c">/* Decode the frame with 15ms deadline */
if&#40;vpx_codec_decode&#40;&amp;codec, frame, frame_sz, NULL, 15000&#41;&#41;
 die_codec&#40;&amp;codec, &quot;Failed to decode frame&quot;&#41;;</pre>

<h2>Codec Specific Postprocessing Controls</h2>

Some codecs provide fine grained controls over their built-in
postprocessors. VP8 is one example. The following sample code toggles
postprocessing on and off every 15 frames.

<pre class="c">#if CONFIG_VP9_DECODER
if&#40;frame_cnt%30 == 1&#41; &#123;
 vp8_postproc_cfg_t pp = &#123;0, 0, 0&#125;;
&nbsp;
 if&#40;vpx_codec_control&#40;&amp;codec, VP8_SET_POSTPROC, &amp;pp&#41;&#41;
 die_codec&#40;&amp;codec, &quot;Failed to turn off postproc&quot;&#41;;
&#125; else if&#40;frame_cnt%30 == 16&#41; &#123;
 vp8_postproc_cfg_t pp = &#123;VP8_DEBLOCK | VP8_DEMACROBLOCK | VP8_MFQE, 4, 0&#125;;
&nbsp;
 if&#40;vpx_codec_control&#40;&amp;codec, VP8_SET_POSTPROC, &amp;pp&#41;&#41;
 die_codec&#40;&amp;codec, &quot;Failed to turn on postproc&quot;&#41;;
&#125;;
#endif</pre>

<h1>Putting It All Together</h1>

<pre class="c">/*
 Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 
 Use of this source code is governed by a BSD-style license
 that can be found in the LICENSE file in the root of the source
 tree. An additional intellectual property rights grant can be found
 in the file PATENTS. All contributing project authors may
 be found in the AUTHORS file in the root of the source tree.
 */
&nbsp;
&nbsp;
/*
 This example adds postprocessing to the simple decoder loop.
 */
#include &lt;stdarg.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;
#define VPX_CODEC_DISABLE_COMPAT 1
#include &quot;./vpx_config.h&quot;
#include &quot;vpx/vp8dx.h&quot;
#include &quot;vpx/vpx_decoder.h&quot;
#define interface (vpx_codec_vp8_dx())
&nbsp;
&nbsp;
#define IVF_FILE_HDR_SZ (32)
#define IVF_FRAME_HDR_SZ (12)
&nbsp;
static unsigned int mem_get_le32&#40;const unsigned char *mem&#41; &#123;
 return &#40;mem&#91;3&#93; &lt;&lt; 24&#41;|&#40;mem&#91;2&#93; &lt;&lt; 16&#41;|&#40;mem&#91;1&#93; &lt;&lt; 8&#41;|&#40;mem&#91;0&#93;&#41;;
&#125;
&nbsp;
static void die&#40;const char *fmt, ...&#41; &#123;
 va_list ap;
&nbsp;
 va_start&#40;ap, fmt&#41;;
 vprintf&#40;fmt, ap&#41;;
 if&#40;fmt&#91;strlen&#40;fmt&#41;-1&#93; != '\n'&#41;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;\n&quot;&#41;;
 exit&#40;EXIT_FAILURE&#41;;
&#125;
&nbsp;
static void die_codec&#40;vpx_codec_ctx_t *ctx, const char *s&#41; &#123;
 const char *detail = vpx_codec_error_detail&#40;ctx&#41;;
&nbsp;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;%s: %s\n&quot;, s, vpx_codec_error&#40;ctx&#41;&#41;;
 if&#40;detail&#41;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot; %s\n&quot;,detail&#41;;
 exit&#40;EXIT_FAILURE&#41;;
&#125;
&nbsp;
&nbsp;
int main&#40;int argc, char **argv&#41; &#123;
 FILE *infile, *outfile;
 vpx_codec_ctx_t codec;
 int flags = 0, frame_cnt = 0;
 unsigned char file_hdr&#91;IVF_FILE_HDR_SZ&#93;;
 unsigned char frame_hdr&#91;IVF_FRAME_HDR_SZ&#93;;
 unsigned char frame&#91;256*1024&#93;;
 vpx_codec_err_t res;
&nbsp;
 &#40;void&#41;res;
 /* Open files */
 if&#40;argc!=3&#41;
 die&#40;&quot;Usage: %s &lt;infile&gt; &lt;outfile&gt;\n&quot;, argv&#91;0&#93;&#41;;
 if&#40;!&#40;infile = fopen&#40;argv&#91;1&#93;, &quot;rb&quot;&#41;&#41;&#41;
 die&#40;&quot;Failed to open %s for reading&quot;, argv&#91;1&#93;&#41;;
 if&#40;!&#40;outfile = fopen&#40;argv&#91;2&#93;, &quot;wb&quot;&#41;&#41;&#41;
 die&#40;&quot;Failed to open %s for writing&quot;, argv&#91;2&#93;&#41;;
&nbsp;
 /* Read file header */
 if&#40;!&#40;fread&#40;file_hdr, 1, IVF_FILE_HDR_SZ, infile&#41; == IVF_FILE_HDR_SZ
 &amp;&amp; file_hdr&#91;0&#93;=='D' &amp;&amp; file_hdr&#91;1&#93;=='K' &amp;&amp; file_hdr&#91;2&#93;=='I'
 &amp;&amp; file_hdr&#91;3&#93;=='F'&#41;&#41;
 die&#40;&quot;%s is not an IVF file.&quot;, argv&#91;1&#93;&#41;;
&nbsp;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;Using %s\n&quot;,vpx_codec_iface_name&#40;interface&#41;&#41;;
 /* Initialize codec */ //
 res = vpx_codec_dec_init&#40;&amp;codec, interface, NULL, //
 VPX_CODEC_USE_POSTPROC&#41;; //
 if&#40;res == VPX_CODEC_INCAPABLE&#41; &#123; //
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;NOTICE: Postproc not supported by %s\n&quot;, //
 vpx_codec_iface_name&#40;interface&#41;&#41;; //
 res = vpx_codec_dec_init&#40;&amp;codec, interface, NULL, flags&#41;; //
 &#125; //
 if&#40;res&#41; //
 die_codec&#40;&amp;codec, &quot;Failed to initialize decoder&quot;&#41;; //
&nbsp;
 /* Read each frame */
 while&#40;fread&#40;frame_hdr, 1, IVF_FRAME_HDR_SZ, infile&#41; == IVF_FRAME_HDR_SZ&#41; &#123;
 int frame_sz = mem_get_le32&#40;frame_hdr&#41;;
 vpx_codec_iter_t iter = NULL;
 vpx_image_t *img;
&nbsp;
&nbsp;
 frame_cnt++;
 if&#40;frame_sz &gt; sizeof&#40;frame&#41;&#41;
 die&#40;&quot;Frame %d data too big for example code buffer&quot;, frame_sz&#41;;
 if&#40;fread&#40;frame, 1, frame_sz, infile&#41; != frame_sz&#41;
 die&#40;&quot;Frame %d failed to read complete frame&quot;, frame_cnt&#41;;
&nbsp;
 #if CONFIG_VP9_DECODER //
 if&#40;frame_cnt%30 == 1&#41; &#123; //
 vp8_postproc_cfg_t pp = &#123;0, 0, 0&#125;; //
 //
 if&#40;vpx_codec_control&#40;&amp;codec, VP8_SET_POSTPROC, &amp;pp&#41;&#41; //
 die_codec&#40;&amp;codec, &quot;Failed to turn off postproc&quot;&#41;; //
 &#125; else if&#40;frame_cnt%30 == 16&#41; &#123; //
 vp8_postproc_cfg_t pp = &#123;VP8_DEBLOCK | VP8_DEMACROBLOCK | VP8_MFQE, 4, 0&#125;;//
 //
 if&#40;vpx_codec_control&#40;&amp;codec, VP8_SET_POSTPROC, &amp;pp&#41;&#41; //
 die_codec&#40;&amp;codec, &quot;Failed to turn on postproc&quot;&#41;; //
 &#125;; //
 #endif //
 /* Decode the frame with 15ms deadline */ //
 if&#40;vpx_codec_decode&#40;&amp;codec, frame, frame_sz, NULL, 15000&#41;&#41; //
 die_codec&#40;&amp;codec, &quot;Failed to decode frame&quot;&#41;; //
&nbsp;
 /* Write decoded data to disk */
 while&#40;&#40;img = vpx_codec_get_frame&#40;&amp;codec, &amp;iter&#41;&#41;&#41; &#123;
 unsigned int plane, y;
&nbsp;
 for&#40;plane=0; plane &lt; 3; plane++&#41; &#123;
 unsigned char *buf =img-&gt;planes&#91;plane&#93;;
&nbsp;
 for&#40;y=0; y &lt; &#40;plane ? &#40;img-&gt;d_h + 1&#41; &gt;&gt; 1 : img-&gt;d_h&#41;; y++&#41; &#123;
 &#40;void&#41; fwrite&#40;buf, 1, &#40;plane ? &#40;img-&gt;d_w + 1&#41; &gt;&gt; 1 : img-&gt;d_w&#41;,
 outfile&#41;;
 buf += img-&gt;stride&#91;plane&#93;;
 &#125;
 &#125;
 &#125;
 &#125;
 <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html">printf</a>&#40;&quot;Processed %d frames.\n&quot;,frame_cnt&#41;;
 if&#40;vpx_codec_destroy&#40;&amp;codec&#41;&#41;
 die_codec&#40;&amp;codec, &quot;Failed to destroy codec&quot;&#41;;
&nbsp;
 fclose&#40;outfile&#41;;
 fclose&#40;infile&#41;;
 return EXIT_SUCCESS;
&#125;</pre>
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