Video Quality
Everyone has different goals when using Permute, so it’s virtually impossible to create a preset that fits everyone’s needs. This is why Permute’s presets come with various options that allow you to customize the preset in a way that fits your needs. Unfortunately, such options can be overwhelming.
This is why Permute comes with a few presets like “Small File” and “High Quality” that are pre-setup MP4 presets for that particular goal. Commonly used presets also have an “Automatic Setup” section that allows you to set up the preset for common use cases like targetting smaller file size. But even that might not be to full satisfaction of everyone.
Triangle of Balance
There are three key aspects of a conversion that go against each other - speed of the conversion, size of the resulting file and visual quality. Let’s call this mystically “Triangle of Balance”. The faster the conversion, the bigger the file, or the lower visual quality. The smaller the file, the longer conversion or the lower visual quality. The better visual quality, the larger file or the longer conversion.
It’s not exactly 1:1:1, but you get the picture. In order to make a small file that maintains the visual quality, the encoder needs to run a lot of analysis on the video in order to detect motions and encode all of that efficiently. This increases the time of the conversion. Otherwise, the file may get bigger. So what to do?
Tips
- Some presets have an “Automatic Setup” section at the very top that allows you to configure the preset for a specific task - for example, focusing on smaller file size, or better quality instead, or in case of iPhone/iPad presets focusing on battery life.
- For H.264 (AVC) and H.265 (HEVC) video formats (used by MP4, HEVC, iPhone and iPad presets), set the video quality to
Custom, run a few tests with different CQ values and decide which one works best for you. CQ stands for Constant Quality and the values for it range between 0 (worst) and 100 (best). The default value for Medium quality is 50, you can get smaller files at 35-40. - Similarly, in case you have disabled hardware acceleration for a preset, Permute offers CRF (Constant Rate Factor) values. It ranges between 0 (best) and 50 (worst). Around 25 is a very decent value, 30-35 is for a faster conversion, smaller files, but slightly worse quality.
- Other formats usually have bitrate options instead, some only have one bitrate (constant) and others two bitrates (bitrate and max bitrate, i.e. variable bitrate). The values to put here are very hard to tell as they will be different for different formats, different resolutions, etc. You will need to experiment a bit more here.
Targeting Specific File Size
With bitrate options, you can target a specific file size (this cannot be done with CQ or CRF as the bitrate varies on the video content). Start with a value that is targeting your desired file size – for example, if you want to reduce a 10-minute (600 seconds) to 50MB, you need bitrate that is (50,000 (kB) / 600 (seconds)) * 8 (8 bits per byte) which gives a bitrate of ~666kbit/s.
Keep maximum bitrate 10-20% above bitrate depending on the amount of action (if you see blockiness during scenes with more movement, increase the max bitrate). If your video has limited motion, you can try lower values.
Either run the conversion on some sample video that is short (~1 minute), or use the Preview button in the Settings window, and see if you are satisfied with the result. If not, increase the bitrate. If yes, try decreasing it (try 50-100kbit/s at a time) until you find the sweetspot you are looking for.