Merge pull request #469 from MobyGamer/deinterlace_updates

Update deinterlacing methods to current best practices

index.html

@@ -108,6 +108,18 @@
     <div class="well">
 
     <h2 id="concepts">Learn about more advanced FFmpeg concepts</h2>
+    <!-- Loop usage explanation -->
+    <label class="recipe" for="batch-loop">Batch and Loop script usage</label>
+    <input type="checkbox" id="batch-loop">
+    <div class="hiding">
+      <h5>Batch and Loop script usage</h5>
+      <p><code>ffmpeg -nostdin -i <em>input_file</em> ...</code></p>
+      <p>One of the frequent uses of FFmpeg is to run batch commands within loops to, for example, generate access files for an entire collection at once.</p>
+      <p>When running an FFmpeg command within a loop it is often necessary to use the <code>-nostdin</code> flag prior to the input in order to ensure successful execution of the commands. This is needed to override FFmpeg's default behavior of enabling interaction on standard input which can result in errors as loop inputs are fed to the ongoing command.</p>
+      <p class="link"></p>
+    </div>
+    <!-- End loop usage explanation -->
+
     <!-- Codec Defaults explanation -->
     <label class="recipe" for="codec-defaults">Codec defaults</label>
     <input type="checkbox" id="codec-defaults">
@@ -213,7 +225,7 @@
         The new container you are rewrapping to is defined by the filename extension used here, e.g. .mkv, .mp4, .mov.</dd>
       </dl>
       <h4>Important caveat</h4>
-      <p>It may not be possible to rewrap a file's contents to a new container without re-encoding one or more of the streams within (that is, the video, audio, and subtitle tracks). Some containers can only contain streams of a certain encoding type: for example, the .mp4 container does not support uncompressed audio tracks. (In practice .mp4 goes hand-in-hand with a H.264-encoded video stream and an AAC-encoded video stream, although other types of video and audio streams are possible). Another example is that the Matroska container does not allow data tracks; see the <a href="#mkv-to-mp4">MKV to MP4 recipe</a>.</p>
+      <p>It may not be possible to rewrap a file's contents to a new container without re-encoding one or more of the streams within (that is, the video, audio, and subtitle tracks). Some containers can only contain streams of a certain encoding type: for example, the .mp4 container does not support uncompressed audio tracks. (In practice .mp4 goes hand-in-hand with a H.264-encoded video stream and an AAC-encoded video stream, although other types of video and audio streams are possible). Another example is that the Matroska container does not allow data tracks.</p>
       <p>In such cases, FFmpeg will throw an error. If you encounter errors of this kind, you may wish to consult the <a href="#transcode">list of transcoding recipes</a>.</p>
       <p class="link"></p>
     </div>
@@ -1397,6 +1409,43 @@
     </div>
     <!-- ends Deinterlace video -->
 
+    <!-- Deinterlace video fields -->
+    <label class="recipe" for="deinterlace_fields">Deinterlace video fields to frames</label>
+    <input type="checkbox" id="deinterlace_fields">
+    <div class="hiding">
+      <h5>Deinterlace video fields to frames</h5>
+      <p><code>ffmpeg -i <em>input_file</em> -c:v libx264 -vf "idet,bwdif,format=yuv420p" <em>output_file</em></code></p>
+      <p>This command takes an interlaced input file and outputs a deinterlaced H.264 MP4, with each field separated into its own frame.  This is preferred for interlaced video that contains a lot of motion, as the double-rate output preserves the visual cadence of the source material.</p>
+      <dl>
+        <dt>ffmpeg</dt><dd>starts the command</dd>
+        <dt>-i <em>input file</em></dt><dd>path, name and extension of the input file</dd>
+        <dt>-c:v libx264</dt><dd>tells FFmpeg to encode the video stream as H.264</dd>
+        <dt>-vf</dt><dd>video filtering will be used (<code>-vf</code> is an alias of <code>-filter:v</code>)</dd>
+        <dt>"</dt><dd>start of filtergraph (see below)</dd>
+        <dt>idet</dt><dd>detect interlaced video field order<br>
+         <a href="https://ffmpeg.org/ffmpeg-filters.html#idet" target="_blank">idet</a> will try to detect if the video is interlaced, and if so, what the order of the fields are (top-field-first, or bottom-field-first).  This is done to ensure the output of the deinterlacing filter is correct.</dd>
+        <dt>bwdif</dt><dd>deinterlacing filter (‘Bob Weaver Deinterlacing Filter’)<br>
+         By default, <a href="https://ffmpeg.org/ffmpeg-filters.html#bwdif-1" target="_blank">bwdif</a> will output one frame for each field, matching the visual cadence of interlaced video. </dd>
+        <dt>,</dt><dd>separates filters</dd>
+        <dt>format=yuv420p</dt><dd>chroma subsampling set to 4:2:0<br>
+        By default, <code>libx264</code> will use a chroma subsampling scheme that is the closest match to that of the input. This can result in Y′C<sub>B</sub>C<sub>R</sub> 4:2:0, 4:2:2, or 4:4:4 chroma subsampling. QuickTime and most other non-FFmpeg based players can’t decode H.264 files that are not 4:2:0, therefore it’s advisable to specify 4:2:0 chroma subsampling.</dd>
+        <dt>"</dt><dd>end of filtergraph</dd>
+        <dt><em>output file</em></dt><dd>path, name and extension of the output file</dd>
+      </dl>
+      <p><code>"idet,bwdif,format=yuv420p"</code> is an FFmpeg <a href="https://trac.ffmpeg.org/wiki/FilteringGuide#FiltergraphChainFilterrelationship" target="_blank">filtergraph</a>. Here the filtergraph is made up of one filter chain, which is itself made up of the three filters (separated by the comma).<br>
+      The enclosing quote marks are necessary when you use spaces within the filtergraph, e.g. <code>-vf "idet, bwdif, format=yuv420p"</code>, and are included above as an example of good practice.</p>
+      <p><strong>Note:</strong> bwdif also supports the older method of outputting one frame for each frame (thereby halving the number of output frames per second) with the syntax <code>bwdif=mode=send_frame</code>.  This can be used when the presentation device is not capable of reproducing 50 (PAL) or 60 (NTSC) frames per second.</p>
+      <p>For more H.264 encoding options, see the latter section of the <a href="#transcode_h264">encode H.264 command</a>.</p>
+      <div class="sample-image">
+        <h2>Example</h2>
+        <p>Before and after deinterlacing with bwdif:</p>
+        <img src="img/interlaced_video_fields.png" alt="VLC screenshot of original interlaced video">
+        <img src="img/deinterlaced_video_frames.png" alt="VLC screenshot of deinterlaced video">
+      </div>
+      <p class="link"></p>
+    </div>
+    <!-- ends Deinterlace video fields -->
+
     <!-- Inverse telecine -->
     <label class="recipe" for="inverse-telecine">Inverse telecine</label>
     <input type="checkbox" id="inverse-telecine">