Answers.Body: <p>The scale filter has no effect on the encoder's bitrate control. </p>
  
  <p>Yes, a scaled down video should have a lower bitrate <strong>if</strong> it is encoded with the same encoder settings as the source. In your command, since no encoder parameters are explicitly set, ffmpeg defaults to encoder <code>x264</code> with rate-control mode CRF with value 23. Apparently, this results in the same bitrate as the full-sized source. Set a higher value to reduce size.</p>
  
  <pre><code>ffmpeg -i input.mp4 -vf scale=2160:2160 -crf 26 output.mp4
  </code></pre>
  
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Answers.CreationDate: 2017-06-06T05:53:22.787Z
Answers.Text: This makes no sense. Why would you have to change crf? That's "constant quality", right? This means that we should expect a lower bitrate on a down scale.
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Answers.Text: @DigiVisionMedia crf is "constant ratefactor". also, this all is searchable in the web, don't be lazy please.
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Answers.CreationDate: 2017-06-06T05:58:27.150Z
Answers.Text: Wouldn't this make a lesser quality encode?
Answers.UserDisplayName: user3643
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Answers.Text: hmm, need 50 rep to comment... so posting instead. **increase** crf to **reduce** bit rate, also reduces quality<br>
  **decrease** crf to **increase** bit rate, improves quality<br>
  +/- 6 crf is about half / double the bitrate (at least for x265). good intro:<br>
  http://slhck.info/video/2017/02/24/crf-guide.html
Answers.UserDisplayName: netjiro
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Body: <p>I have a 3000 by 3000 VR video encoded in H264. I scaled down the video by</p>
  
  <pre><code>ffmpeg -i input.mp4 -vf scale=2160:2160 output.mp4
  </code></pre>
  
  <p>To my surprise, the bit rate of <code>output.mp4</code> did not decrease (in fact, it increased a little bit).</p>
  
  <p>Is not a scaled down video supposed to have lower bit rate than the original video? What is the mechanism of <code>-vf scale=***</code>?</p>
  
Tags: <ffmpeg><scale><libx264>
Title: I scaled down a video, but the bit rate does not change
UserDisplayName: shintaroid
ThreadText: # I scaled down a video, but the bit rate does not change
  
  (Asked by: username_0 on 2017-06-05)
  
  I have a 3000 by 3000 VR video encoded in H264. I scaled down the video by
  
  ```
  ffmpeg -i input.mp4 -vf scale=2160:2160 output.mp4
  
  ```
  
  To my surprise, the bit rate of `output.mp4` did not decrease (in fact, it increased a little bit).
  
  Is not a scaled down video supposed to have lower bit rate than the original video? What is the mechanism of `-vf scale=***`?
  
  **Tags:** ffmpeg, scale, libx264
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2017-06-06. Score: 1 | Accepted answer
  
  The scale filter has no effect on the encoder's bitrate control.
  
  Yes, a scaled down video should have a lower bitrate **if** it is encoded with the same encoder settings as the source. In your command, since no encoder parameters are explicitly set, ffmpeg defaults to encoder `x264` with rate-control mode CRF with value 23. Apparently, this results in the same bitrate as the full-sized source. Set a higher value to reduce size.
  
  ```
  ffmpeg -i input.mp4 -vf scale=2160:2160 -crf 26 output.mp4
  
  ```
  
  > **Comments:**
  > **username_2**: This makes no sense. Why would you have to change crf? That's "constant quality", right? This means that we should expect a lower bitrate on a down scale.  
  > **username_3**: @DigiVisionMedia crf is "constant ratefactor". also, this all is searchable in the web, don't be lazy please.  
  > **username_2**: Wouldn't this make a lesser quality encode?  
  > **username_4**: hmm, need 50 rep to comment... so posting instead. **increase** crf to **reduce** bit rate, also reduces quality<br> **decrease** crf to **increase** bit rate, improves quality<br> +/- 6 crf is about half / double the bitrate (at least for x265). good intro:<br> http://slhck.info/video/2017/02/24/crf-guide.html  
  
  ---
  
  