Answers.Body: <p>There are a few video quality metrics available for you to use, primarily <a href="https://en.wikipedia.org/wiki/Structural_similarity" rel="nofollow">SSIM</a> and also <a href="https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio" rel="nofollow">PSNR</a>. You can use <a href="https://ffmpeg.org/download.html" rel="nofollow">ffmpeg</a> to convert the video and then compare the output.</p>
  
  <p><strong>Step 1</strong> Convert the video</p>
  
  <pre><code>ffmpeg -i actioncamfile -c:v libx264 -crf 23 -c:a copy -map 0 compressed.mp4
  </code></pre>
  
  <p>The CRF value modulates the quality. Lower values produce better quality but larger file sizes. Typical values range from 18 to 28, but absolute range is 0 to 51, but 0 being lossless, which will produce an exact looking file but will be bloated.</p>
  
  <p>If you want to test with only a small section, say 20 seconds of the source starting from 15 seconds into the file, you can use</p>
  
  <pre><code>ffmpeg -ss 15 -i actioncamfile -t 20 -c:v libx264 -crf 23 -c:a copy -map 0 compressed.mp4
  </code></pre>
  
  <p><strong>Step 2</strong> Measure the quality of the conversion</p>
  
  <p>Run</p>
  
  <pre><code>ffmpeg -i compressed.mp4 -i actioncamfile -lavfi "ssim;[0:v][1:v]psnr" -f null -
  </code></pre>
  
  <p>This command output, at its end, will display lines like this</p>
  
  <pre><code>[Parsed_ssim_0 @ 000000000039ad80] SSIM Y:0.984483 U:0.980458 V:0.980921 All:0.983219 (17.751712)
  [Parsed_psnr_1 @ 0000000000398320] PSNR y:42.63 u:43.19 v:44.09 average:42.90 min:42.07 max:46.16
  </code></pre>
  
  <p>You can aim for a SSIM <code>All</code> value to be at least 0.99, or set your own benchmark, based on what's acceptable.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-02-10T13:51:15.297Z
Answers.Text: For some reason, All: stays at 0.7 no matter what crf is like between 18 and 37. My commands: http://pastebin.com/asQrmmq0
Answers.UserDisplayName: Vitalis Hommel
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-02-10T13:54:27.627Z
Answers.Text: Try without `-ss`
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-03T03:00:17.643Z
Answers.Text: If you are just looking at SSIM to be over 0.99, do you need to include `;[0:v][1:v]psnr` in the command?
Answers.UserDisplayName: pacoverflow
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-02-10T05:15:52.537Z
Answers.LastActivityDate: 2016-02-10T05:15:52.537Z
Answers.UserDisplayName: Gyan
Body: <p>This is the best my actioncam can create.</p>
  
  <p><a href="https://i.sstatic.net/0GbFx.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0GbFx.jpg" alt="Rollei Wifi 5S"></a></p>
  
  <p>My goal is to take advantage of this low quality and save as much harddrive space as possible so visible quality remains.</p>
  
  <p>Which measurements can I take using which windows programs to exploit the already low quality and save as much space as possible?</p>
  
Tags: <video><software-recommendation><video-quality><compression><recommendation>
Title: Which measurements can I take using which programs to exploit the already low quality and save as much space as possible?
UserDisplayName: Vitalis Hommel
ThreadText: # Which measurements can I take using which programs to exploit the already low quality and save as much space as possible?
  
  (Asked by: username_0 on 2016-02-10)
  
  This is the best my actioncam can create.
  
  [![Rollei Wifi 5S](https://i.sstatic.net/0GbFx.jpg)](https://i.sstatic.net/0GbFx.jpg)
  
  My goal is to take advantage of this low quality and save as much harddrive space as possible so visible quality remains.
  
  Which measurements can I take using which windows programs to exploit the already low quality and save as much space as possible?
  
  **Tags:** video, software-recommendation, video-quality, compression, recommendation
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2016-02-10. Score: 3 | Accepted answer
  
  There are a few video quality metrics available for you to use, primarily [SSIM](https://en.wikipedia.org/wiki/Structural_similarity) and also [PSNR](https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio). You can use [ffmpeg](https://ffmpeg.org/download.html) to convert the video and then compare the output.
  
  **Step 1** Convert the video
  
  ```
  ffmpeg -i actioncamfile -c:v libx264 -crf 23 -c:a copy -map 0 compressed.mp4
  
  ```
  
  The CRF value modulates the quality. Lower values produce better quality but larger file sizes. Typical values range from 18 to 28, but absolute range is 0 to 51, but 0 being lossless, which will produce an exact looking file but will be bloated.
  
  If you want to test with only a small section, say 20 seconds of the source starting from 15 seconds into the file, you can use
  
  ```
  ffmpeg -ss 15 -i actioncamfile -t 20 -c:v libx264 -crf 23 -c:a copy -map 0 compressed.mp4
  
  ```
  
  **Step 2** Measure the quality of the conversion
  
  Run
  
  ```
  ffmpeg -i compressed.mp4 -i actioncamfile -lavfi "ssim;[0:v][1:v]psnr" -f null -
  
  ```
  
  This command output, at its end, will display lines like this
  
  ```
  [Parsed_ssim_0 @ 000000000039ad80] SSIM Y:0.984483 U:0.980458 V:0.980921 All:0.983219 (17.751712)
  [Parsed_psnr_1 @ 0000000000398320] PSNR y:42.63 u:43.19 v:44.09 average:42.90 min:42.07 max:46.16
  
  ```
  
  You can aim for a SSIM `All` value to be at least 0.99, or set your own benchmark, based on what's acceptable.
  
  > **Comments:**
  > **username_0**: For some reason, All: stays at 0.7 no matter what crf is like between 18 and 37. My commands: http://pastebin.com/asQrmmq0  
  > **username_1**: Try without `-ss`  
  > **username_2**: If you are just looking at SSIM to be over 0.99, do you need to include `;[0:v][1:v]psnr` in the command?  
  
  ---
  
  