Video Quality?

[root012]

When I upload some video, video it's automatically converted to 480p 720p and 1080p but I upload 1.5GB videos and video with 1080p use only 250-300mb and quality is very bad. Could you please tell me where is the problem?

[Tech Support]

Video quality depends on FFmpeg options that you use in Settings -> Video Formats. Specifically there is an option named -crf <number> which controls rate factor (it is called Constant Rate Factor):

 

 

Here is what KVS documentation says:

 

The -crf 25 parameter sets the video quality factor (the less this value, the higher the quality). When you use this parameter, the videos will be encoded with permanent quality and dynamic bitrate. It means that video fragments where quality loss is not critical (motion pieces etc) will be encoded with lower quality. At the same time, fragments where quality loss would be noticeable will have higher quality and higher bitrate. A possible disadvantage here is that you can't predict file size and requires a few test iterations before you establish values that work best for you. We recommend setting this parameter to a value between 20 and 35.

 

You can read more about CRF here:

https://slhck.info/video/2017/02/24/crf-guide.html

[Diego12220]

as always tech support resolved my problem as well! thanks!

Edited August 24, 2021 by Diego12220

[Lococent]

do I lose the quality of the video after I edit it in some application (for example, in inshot) and then upload it in KVS?

[Tech Support]

It depends on what you do in your video editor and how you then save this video. Every time you need to re-convert a video you are losing some small portion of its original quality. This is like re-saving JPG image many times:

https://improvephotography.com/2484/does-saving-a-jpeg-multiple-times-reduce-image-quality/

However in practice if you don't re-save with poor compression ratio the visual quality loss will be unnoticeable.

[Diego12220]

On 8/28/2021 at 5:14 AM, Lococent said:

do I lose the quality of the video after I edit it in some application (for example, in inshot) and then upload it in KVS?

In fact, if you edit in inshot and then upload the video to kvs, then you are unlikely to lose much in the quality of the file, just as if you were editing in this video editor (I'm just giving it as an example because I use it). But if you edit a video in some online editor, it can spoil the quality of the video more than any other editor.