YouTube, qualité des vidéos 1080 uploadée = qualité médiocre

Sebulba on m'a encore répondu

Do you have a link? Is it the same type of content, fast moving content with a lot of detail?

Here's a video from Red Bull, a very large partner:
Notice how it turns to crap as soon as it starts moving through trees and with a lot of movement.
Another that has similar boat footage:

The complexity of the scene and the amount of differences between one frame to the next frame can have a dramatic impact on the final quality of the video because more changes from frame to frame it will require a much higher bitrate to preserve the detail in those frames. Most compression algorithms for video are able to compress video from frame to frame (temporal compression) by borrow parts from previous frames rather than encoding the entire frame. So for example if you had a black circle on a white background...the black circle moves from side to side...in the compression, the encoding can borrow parts of the frame that don't change that much, so subsquent frames may only include the new position of the black circle while borrowing the white portion of parts of the frame from a previous frame. No need to waste bits on encoding parts of the frame that didn't change.
So in the case where there is a lot of movement it requires a higher bitrate because there is less that it can borrow from other frames...so things start to fall apart and macro block loosing the quality.
Simpler less complex scenes will encode better and look better.

So there isn't much that can be done because ultimately you are at the mercy of how YouTube chooses to encode the video and the bitrates they are using.

As an experiment, take some of that swamp footage and slow it down to half speed.
Take some of the swamp footage and apply a little bit of blur to the video to reduce the amount of detail and complexity in the trees and water.

Both of those will end up looking better once uploaded to YouTube.