Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of video infrastructure technologist Harmonic Inc (NASDAQ:HLIT) sank 10% today after its preliminary Q2 results and outlook disappointed Wall Street.

So what: Harmonic shares have slumped in recent weeks on worries over a slowdown in demand, and today's preliminary Q2 miss -- adjusted EPS of about $0.01 on revenue of roughly $109 million vs. the consensus of $0.06 and $118.32 million -- coupled with downbeat Q3 guidance only confirms those concerns. In fact, Harmonic expects Q2 gross margin in the range of 49% to 51%, versus management's prior view of about 53%, suggesting that its competitive position is weakening at a faster rate than expected. 

Now what: Management now sees Q3 revenue of $103 million to $113 million, well below the consensus of $124.8 million. "Looking ahead, while the transitioning video market is turbulent and we are consequently cautious about our near-term results, the growing signs of coming video technology investment cycles and our cable customers' continuing positive response to our CCAP products are encouraging," President and CEO Patrick Harshman reassured investors. "We therefore remain positioned and focused on achieving the company's overarching objectives for driving sustainable top and bottom line growth." Given Harmonic's still-questionable competitive moat and steep-ish P/E of about 30, however, I'd hold out for an even wider margin of safety before buying into that turnaround talk. 

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Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.