I found this post with basically the same issue, or very close
The difference I have is that I can play back Bluray movies with H.264 acceleration fine. I don't have hard drives stopping as well.
I have just been playing back video content and watching my GPU usage / temperature.
When the flash video goes all choppy its because the system is not using the GPU in the video card. Normally the gpu sits between 60-85% usage when doing hardware smoothing on the video stream. As soon as it turns it off (why it turns off I am not sure) the video goes to being choppy.
If I pause the video stream and give it about 1 minute and then press play again, the flash video stream starts using the GPU again.
If I pause and play after just a few seconds, the GPU is not engaged. So I am wondering if its turning the hardware acceleration off because of power or temperature.
I am going to try removing one or two hard drives and see what happens.
I thought turning aero off fixed the problem, but after some more testing today I found that it is still there, it just seems to take a little longer.
Its definately that GPU support seems to be switching off for some reason. Don't know if its a driver bug or flash.
I also have just been testing youtube clips as a comparison, but I don't seem to have any issues on youtube. So it seems site specific. Could it be content encoding? I know the ABC site has a video smoothing tickbox in their options on the flash site, but turning it off doesn't affect the bug.
Ahh computers.... wish they would just work! I have been fiddling around with the pc for a few weeks, last issue I just sorted out was ATI stream not working on my HD 2600. Turn out to be a motherboard incompatibility. Got an intel chipset board and ATI stream works fine.
Anyway.... anyone got any ideas?
Just tested this 720p HD flash video stream and it pays page fine as well
So it seems to be site specific... but the bug doesn't happen under XP, only Windows 7 (don't have vista to try).... The ABC site works perfectly fine on my older ATI 9600 under windows 7, so its site specific with my ATI HD 2600 Pro AGP to be more specific....
Does anyone know if there is a debug version of flash that can tell me why it turns off the GPU acceleration after a few minutes?
I also found that disabling Hardware Acceleration in Flash dosen't seem to make a difference. The GPU still does video processing for a bit and then when the GPU drops to 20% and then after a few seconds 0% the video goes all choppy. So maybe its to do with the ATI AVIVO video processing that the card is trying to apply to the video?
However once more its only the abc site.
I have found that the problem extends to youtube and other flash based websites, but only under Windows 7. When playing back HD clips, such as 720p test clips on youtube, it will play fine for about 30 seconds to 1 minute, and then it seems to drop the GPU usage and go 100% CPU at which point frame rates drop from about 30fps to about 4 fps.
The funny thing is my laptop which has an older ATI 9600 can play these same video clips at 30fps and doesn't have any issues, whereas the newer ATI HD 2600 Pro AGP card turns to putty.
Once the issue has started, i need to close internet explorer and terminate the flash player from memory for it to go back to normal for a bit. It seems to particularly manifest the problem on you tube with high def clips.
Well some good news as far as video playback, not for adobe flash, but the flash video's. I can download the flash videos and play them back in both VLC and Arcsoft Total Media theatre without any of the video playback issues. So it looks like its Adobe Flash thats the problem.
I can download a youtube 1080p h.264 image and play back the clip under Arcsoft Total Media Theatre 3 and only be using 11% of my CPU (an old P4 3.0Ghz Hyperthreaded cpu) as Arcsoft provides hardware acceleration of the clips.
Now if Arcsoft can provide hardware acceleration on an ATI HD 2600 Pro AGP video card, surely ATI and Adobe can do the same for flash and also fix the bug in flash that makes flash stop using the video card GPU after a short period of time.
I tried this 720p clip using Windows 7 64bit and I get a stutter every
4 or 5 seconds.
This morning I upgraded to the latest Flash update.
The videos on my website are showing the same behavior, a stutter every 5 seconds like a buffer is being emptied.
This happens even after the progress bar shows the file as being downloaded.
I have an ATI 4850 video card.
Other forums where I have posted about this to try get resolution
Windows 7 forum
A few people had fixed their problem by vacuuming their CPU heat sink / fan. So I thought, what the heck, doesn't sound like a solution but I will give it a go. And it has fixed my problem. So the dust on the heat sink (which it had a bit as it was a few years old), looks like the problem, well more specifically the CPU getting to hot.
Although I don't suppose that every user will be comfortable with pulling their CPU heat sink apart, it did fix my problem.
I also had noticed that my Hardware Acceleration in Windows Media Center would stop, so it got me to thinking it wasn't just Flash that was turning off Hardware Acceleration. I mainly noticed this when watching High Definition tv, which puts more CPU load on the system.