If you happen to run old Computer hardware with lets say 256 or 512 MB of memory, a CPU of 600-800Mhz and a small hard disk like 5 / 10 GB and you need to have Flash Player on Firefox play Videos in Youtube and Vimeo with as less obstructions as possible, it is useful to take a look and try tuning up browser caching values, to do so type in URL Address Bar
Then search for;
Raise (tune up) the values for:
Try to raise this value with 50% (524288), (1048576 + 524288) = 1572864.
By default, as you see
browser.cache.disk.enable is set to false
Try to change it to true, as this might have positive effect on flash video buffering and thus improve a bit experience.
Again it is good practice to try raise it with 50% and test if Flash Player performs better. I.e. (358318/2) = 179159, (358318+179159) = 537477. Hence raise it too lets say 358318. I give the 50%, example because the cache size on Firefox (IceWeasel) will differ depending on the browser version Linux distro and architecture.
There are few other caching, variables to tune, though I doubt if they will have impact on Flash Player performance it is good to know they're there. To see all Mozilla caching variables in Search filed, type "cache". One other non Flash Player performance related variable to check and tune is:
In time of writting on my Firefox ver. 18.0.1 it is set to 5242880.
I'm looking forward to hear if this little tuning tips helped improve Flash Player. If you happen to have some positive impact on Video flow, please drop a comment with Linux distribution type and version, Flash Player version and changed caching variables.
Hope this little post helps. Happy tuning