Thanks for using the answers forums! That's a great question! There is a way to do so. I will post for how to do this for both MAC and PC in case any MAC users have the same question and find this thread in their search.
This would have to be done in the Desktop SlingPlayer, rather than the web versions.
Here is the link for both Mac and PC downloads for the Desktop SlingPlayer:
This article provides some information about this as well:
On a PC, please navigate to: SlingPlayer > Click on Settings > select SlingPlayer Options > click on Encoding tab. This is where you can change the Audio and Video bitrates as needed.
For Mac users, please navigate to: System preferences and select Encoding tab
Hope this helps!
The Sling Moderation Team