You are not the only one with this, I am having this issue also,
Out curiosity are you on Windows or Mac/Linux, i am using Linux, i don´t know if this is a Linux client issue.
Are you using a computer that is so old it still uses a CRT monitor because if so then you will never probably have any decent quality. Just taking a guess here.
hmmm Change codecs? Try that and lets see what happens. Sometimes each codec may work for one person but not another.