This type of volume has not been seen in a little while, but it is not exactly atypical. If you look back over the past 2 years, there have been quite a few days where more than 500,000 shares traded, and a few where it even got to a million.
The interesting thing about the other day is that 80% of the volume can be explained by five larger trades. 350,000 shares were traded in three large blocks before the price went up. There was then a spike in the late morning, which is bracketed by two 25,000 share trades at lower prices (that is probably the cost of moving larger blocks on a low volume asset). The price was actually driven up by individual investors buying small blocks, not instituional purhcases.
I wonder if there is a little leak of info around Avid, or if investors are just noticing that (1) Q4-Q1 is usually a very good period for Avid stock and (2) there is already strong momentum building. The technical analysts would probably have a field day in this situation, but they are probably not covering this stock.