<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>

CC BY-SA 3.0
2016-02-10T13:51:15.297Z
For some reason, All: stays at 0.7 no matter what crf is like between 18 and 37. My commands: http://pastebin.com/asQrmmq0
Vitalis Hommel
CC BY-SA 3.0
2016-02-10T13:54:27.627Z
Try without `-ss`
Gyan
CC BY-SA 4.0
2023-04-03T03:00:17.643Z
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?
pacoverflow
CC BY-SA 3.0
2016-02-10T05:15:52.537Z
2016-02-10T05:15:52.537Z
Gyan
<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>

<video><software-recommendation><video-quality><compression><recommendation>
Which measurements can I take using which programs to exploit the already low quality and save as much space as possible?
Vitalis Hommel
# 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


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## 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 and also PSNR. You can use ffmpeg 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?  

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