Question / Help Video quality

[JeremyMix]

Hello,

I have the version 25 on Windows, I use it in order to take vidéo of a game, but the image quality is not very sharp. For example towards the end of the video we see that the red text at the bottom left is blurred, and the colors are less clear than in reality throughout the video.

I have a GTX 1080 with i7.

https://www.youtube.com/watch?v=8pJfQ0EeCAM

Some parameters:
Encoder NVENC
Bitrate 6000
Video quality: Very good quality, large file size
60 FPS
Video format flv that I convert on mp4
Color space: 709
YUV color range: Full

I tried making modifications here and there but it didn't improve anything.

Here is a screenshot of the game with good quality.

Thank you in advance

 

[Tomasz Góral]

Change color space to 601, source resolution is 720p ?

 

[carlmmii]

Color space should be kept at 709. It has no bearing on actual compression quality, just color mapping between source encoding and destination. The color range should be changed to partial though.

The problem you're encountering is that your source image is about as complex as it comes for video compression:
- Sharp contrast
- Crisp edges
- Complex textures (the grass)
- Fine text
- Colored text

You may notice that even saving a still image as a jpg, you would have to crank the quality/file size up quite a bit to have a decent image. It's the same problem with video encoding.

On top of that, there's the chroma subsampling to deal with. That is what is destroying your text, specifically red and green text. Nvenc can only do NV12 compression, which is 4:2:0. Basically, less actual detail in colors, especially strong colors with high contrast against the surroundings.

You could try changing your color mode and using x264 (just don't use xRGB, as this doesn't leverage GPU compositing), but ultimately that only helps mitigate one of the problems. The main problem you have is that you just won't have enough bitrate for the complexity that is being sent through the encoder.

Things that would help:
- Increasing bitrate (general suggestion -- if you're already at 6000kbps on twitch, there's no real headroom here)
- lowering resolution
- lowering framerate
- using a higher quality encoder (such as x264 on faster or better)

 

[JeremyMix]

Hello,

Sorry for the late answer.

I changed yet the color range to partial.

Thank you for the explanations, yet I understand better why the wuality is lower as on a screenshot. I changed the paramater to x264 and the bitrat to 6000. I had a framerate of 60, I lowered this to 48.

Regarding the resolution, I clicked to automatically adapt it to the window. That is why I do not have black bands on the left and right despite the 4: 3 format of the game.

I used NV12 compression:

2020 04 20 17 46 34

www.youtube.com

The problem does not seem to has been resolved.

Here with I420 compression:

2020 04 20 17 50 52

www.youtube.com

Here with I444 compression:

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

www.youtube.com

Here with I444 compression and a bitrate of 10000 (before it was 6000):

2020 04 20 17 56 45

www.youtube.com

With I420 compression and bitrate of 10000:

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

www.youtube.com

With I420 compression and bitrate of 15000:

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

www.youtube.com

With I420 compression and bitrate of 15000 and framerate of 30 (before 48):

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

www.youtube.com

I think I tried everything ...

 

[koala]

On Youtube it looks all the same, because Youtube recodes everything to 4:2:0 (NV12) color space. One characteristic of this color space is you get a slightly changed red and green if you have letters in pure red or pure green. This is something you cannot change with Youtube.