I'm connecting my aspire 6920 running W7 with a vga cable to a Samung series 5 lcd tv. When i open a .avi file on the laptop it runs fluently for about 2 minutes, and then suddenly it hangs every 3s for a very short time. How is this possible?
I also notice that when the video starts to hang, the cpu is repeatedly busy for a short time.
Yes, this is what computer manufacturers generally don't tell you when you buy a computer. The memory of the computer needs to be sufficient, both in processor cache and RAM, to handle the video stream or playback. Also, it won't hurt to have a video card with at least 500 mb memory and a separate video GPU graphics processor unit. This means an external PCI video card (8X or 16X). Motherboards that come with on-board video will have a very limited amount of processor and RAM that is dedicated to the video process. Laptops will have even less.
As you notice, when the processor loads up to around 80 to 100 percent the video beguines jitterbugging or freezing, like an old time movie show, and does not play smoothly. The smaller the viewing area (less memory required) the less noticeable the jitter becomes. The larger the viewing area (more memory required) the more freezing will occur, the process cache is full when the picture freezes.
As long as the cache is never full, the video never freezes. That's the advantage of the newer quad core processors, like the AMD Phenom with 6 mb, or the intel i5, i7, with even more cache memory.
Just adding a video card or more RAM will not fix the problem. It still needs to go through the CPU before addressing the RAM and video card, hence an upgrade does not solve it.
Then reducing the size of the playback area like 1/2 screen or less, not full screen, will make the problem go away, less memory required.
You can expect to invest about $1000 (if you build it yourself) on an AMD socket 3 system, and even more for an intel based system, to get really smooth cinema theater quality playback. So save up and get a quad core, DDR3 memory, external PCI video, and you will be very happy building a system around that format, these boards also have great sound quality.