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add note about dither methods to the audio recipes. Recently, I noticed a strange pheonomenon with the previous dither method where the FFMPEG resampler would greatly increase the gain.

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jamessam 2017-08-20 15:46:41 -07:00
parent 6c85518288
commit 7f1a765dd8
1 changed files with 6 additions and 4 deletions
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@ -324,13 +324,14 @@
<dl> <dl>
<dt>ffmpeg</dt><dd>starts the command</dd> <dt>ffmpeg</dt><dd>starts the command</dd>
<dt>-i <i>input_file</i></dt><dd>path and name of the input file</dd> <dt>-i <i>input_file</i></dt><dd>path and name of the input file</dd>
<dt>-write_id3v1 <i>1</i></dt><dd>Write ID3v1 tag. This will add metadata to the old MP3 format, assuming you’ve embedded metadata into the WAV file.</dd> <dt>-write_id3v1 <i>1</i></dt><dd>Write ID3v1 tag. This will add metadata to the "older" MP3 metadata format that's found at the head of the file, assuming you’ve embedded metadata into the WAV file.</dd>
<dt>-id3v2_version <i>3</i></dt><dd>Write ID3v2 tag. This will add metadata to a newer MP3 format, assuming you’ve embedded metadata into the WAV file.</dd> <dt>-id3v2_version <i>3</i></dt><dd>Write ID3v2 tag. This will add metadata to the "newer" MP3 metadata format that's found at the tail of the file, assuming you’ve embedded metadata into the WAV file.</dd>
<dt>-dither_method <i>modified_e_weighted</i></dt><dd>Dither makes sure you don’t unnecessarily truncate the dynamic range of your audio.</dd> <dt>-dither_method <i>rectangular</i></dt><dd>Dither makes sure you don’t unnecessarily truncate the dynamic range of your audio.</dd>
<dt>-out_sample_rate <i>48k</i></dt><dd>Sets the audio sampling frequency to 48 kHz. This can be omitted to use the same sampling frequency as the input.</dd> <dt>-out_sample_rate <i>48k</i></dt><dd>Sets the audio sampling frequency to 48 kHz. This can be omitted to use the same sampling frequency as the input.</dd>
<dt>-qscale:a <i>1</i></dt><dd>This sets the encoder to use a constant quality with a variable bitrate of between 190-250kbit/s. If you would prefer to use a constant bitrate, this could be replaced with <code>-b:a 320k</code> to set to the maximum bitrate allowed by the MP3 format. For more detailed discussion on variable vs constant bitrates see <a href="https://trac.ffmpeg.org/wiki/Encode/MP3" target="_blank">here.</a></dd> <dt>-qscale:a <i>1</i></dt><dd>This sets the encoder to use a constant quality with a variable bitrate of between 190-250kbit/s. If you would prefer to use a constant bitrate, this could be replaced with <code>-b:a 320k</code> to set to the maximum bitrate allowed by the MP3 format. For more detailed discussion on variable vs constant bitrates see <a href="https://trac.ffmpeg.org/wiki/Encode/MP3" target="_blank">here.</a></dd>
<dt><i>output_file</i></dt><dd>path and name of the output file</dd> <dt><i>output_file</i></dt><dd>path and name of the output file</dd>
</dl> </dl>
<p>A note about dither methods. FFMPEG comes with a variety of dither algorithms, outlined in the <a href="https://ffmpeg.org/ffmpeg-resampler.html" target="_blank" rel="noopener noreferrer">official docs</a>, though some may lead to unintended, not-subtle digital clipping on some systems.</p>
<p class="link"></p> <p class="link"></p>
</div> </div>
</div> </div>
@ -352,10 +353,11 @@
<dt>-i <i>input_file</i></dt><dd>path and name of the input file</dd> <dt>-i <i>input_file</i></dt><dd>path and name of the input file</dd>
<dt>-c:a aac</dt><dd>sets the audio codec to AAC</dd> <dt>-c:a aac</dt><dd>sets the audio codec to AAC</dd>
<dt>-b:a 128k</dt><dd>sets the bitrate of the audio to 128k</dd> <dt>-b:a 128k</dt><dd>sets the bitrate of the audio to 128k</dd>
<dt>-dither_method modified_e_weighted</dt><dd>Dither makes sure you don’t unnecessarily truncate the dynamic range of your audio.</dd> <dt>-dither_method rectangular</dt><dd>Dither makes sure you don’t unnecessarily truncate the dynamic range of your audio.</dd>
<dt>-ar 44100</dt><dd>sets the audio sampling frequency to 44100 Hz, or 44.1 kHz, or “CD quality”</dd> <dt>-ar 44100</dt><dd>sets the audio sampling frequency to 44100 Hz, or 44.1 kHz, or “CD quality”</dd>
<dt><i>output_file</i></dt><dd>path and name of the output file</dd> <dt><i>output_file</i></dt><dd>path and name of the output file</dd>
</dl> </dl>
<p>A note about dither methods. FFMPEG comes with a variety of dither algorithms, outlined in the <a href="https://ffmpeg.org/ffmpeg-resampler.html" target="_blank" rel="noopener noreferrer">official docs</a>, though some may lead to unintended, not-subtle digital clipping on some systems.</p>
<p class="link"></p> <p class="link"></p>
</div> </div>
</div> </div>