Answers.Body: <p>I was able to find an answer. <a href="https://stackoverflow.com/a/14308561/941493">https://stackoverflow.com/a/14308561/941493</a>.</p>
  
  <p>In the nutshell, CRF calculation is also affected by preset so the same CRF number is not the same with different presets. Based on some developer difference can be mostly ignored.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-04-28T14:35:22.040Z
Answers.Text: That's a bit of a gotcha. I didn't know that, thanks.
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Answers.CreationDate: 2020-04-26T17:41:05.833Z
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Answers.UserDisplayName: Tomas
Body: <p>I am experimenting with ffmpeg and x264 codec. And I have found some unexpected behaviour.</p>
  
  <p>I am encoding video with parameters CRF 23, high profile and changing preset.  <a href="https://trac.ffmpeg.org/wiki/Encode/H.264" rel="nofollow noreferrer">Documentation</a> says:</p>
  
  <blockquote>
    <p>for constant quality encoding, you will simply save bitrate by choosing a slower preset.</p>
  </blockquote>
  
  <p>And I am using CRF, so it should be this particular quote. So how is possible that I have achieved the smallest file for <code>veryfast</code> preset?</p>
  
  <pre><code>medium    256MB
  fast      261MB
  faster    235MB
  veryfast  209MB
  superfast 324MB
  </code></pre>
  
  <p>What am I missing? BTW another <a href="https://write.corbpie.com/ffmpeg-preset-comparison-x264-2019-encode-speed-and-file-size/" rel="nofollow noreferrer">comparison</a> have similar results.</p>
  
Tags: <ffmpeg><h.264>
Title: ffmpeg with h264 produces smaller file sizes for veryfast preset
UserDisplayName: Tomas
ThreadText: # ffmpeg with h264 produces smaller file sizes for veryfast preset
  
  (Asked by: username_0 on 2020-04-26)
  
  I am experimenting with ffmpeg and x264 codec. And I have found some unexpected behaviour.
  
  I am encoding video with parameters CRF 23, high profile and changing preset. [Documentation](https://trac.ffmpeg.org/wiki/Encode/H.264) says:
  
  > for constant quality encoding, you will simply save bitrate by choosing a slower preset.
  
  And I am using CRF, so it should be this particular quote. So how is possible that I have achieved the smallest file for `veryfast` preset?
  
  ```
  medium    256MB
  fast      261MB
  faster    235MB
  veryfast  209MB
  superfast 324MB
  
  ```
  
  What am I missing? BTW another [comparison](https://write.corbpie.com/ffmpeg-preset-comparison-x264-2019-encode-speed-and-file-size/) have similar results.
  
  **Tags:** ffmpeg, h.264
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2020-04-26. Score: 1
  
  I was able to find an answer. <https://stackoverflow.com/a/14308561/941493>.
  
  In the nutshell, CRF calculation is also affected by preset so the same CRF number is not the same with different presets. Based on some developer difference can be mostly ignored.
  
  > **Comments:**
  > **username_1**: That's a bit of a gotcha. I didn't know that, thanks.  
  
  ---
  
  