Encoding x265 seems slower than necessary

[Epaminaidos]

Hi,

I am currently encoding some videos using handbrakeCLI and x265 on my notebook (i7-6700HQ, 4 cores, 8 threads, hdd, 16GB RAM).

But for some reason, the task manager shows a CPU usage of only about 50-60% (and only 33% by handbrakeCLI).

Is it normal that this does not show up to 100%?

And should I be concerned about the CPU-temperature (90-96°C)? According to the task manager, the frequency stays at about 2.80GHz, which seems to be ok for a 2.60GHz CPU though.

On another machine of mine (celeron, 2 cores, 2 threads, hdd, 4GB RAM), the CPU is used to about 90% (both: total and handbrakeCLU), which seems much better.

Is there anything I can do to improve performance on the notebook as well?

[LigH.de]

Is it normal that this does not show up to 100%?

Yes. Already explained so many many times before ... HEVC is a much more complex algorithm, many parts of it need to wait for intermediate results to be completed before they can continue. It is not as parallelizable as e.g. AVC (x264). But ... it still utilizes your CPU a lot more if it supports vectorized SIMD instruction sets, especially AVX2. Such instructions may not work well along with HyperThreading or with excess threads, though (if as many threads as cores are already busy, all other threads will pause).

So your i7 with 4 physical cores and support for better SIMD instruction sets will probably be faster than your Celeron with only 2 cores and limited instruction sets, even though only 4 of the 8 virtual (HT) cores are active.

[Epaminaidos]

Thank you for the response and explanation.
And sorry for not researching this before. I started this post wanting to ask if this kind of temperatures is normal during encoding on a notebook. But after some editing, I ended up asking the more general question about the 50%. And I totally forgot to research this before.

[Epaminaidos]

So your i7 with 4 physical cores and support for better SIMD instruction sets will probably be faster than your Celeron with only 2 cores and limited instruction sets, even though only 4 of the 8 virtual (HT) cores are active.

Yes, it is faster, but not be the margin, I expected (only about 30-50%).

[jagabo]

Handbrake with x265 has no problem using nearly 100 percent of my quad core CPU (5 i2500K). You have a bottleneck somewhere -- reading the source or filtering.

95 degrees C is very high, especially with only 50 percent CPU usage. You should look into better cooling. My i5 only goes a little above 50C when encoding at 100 percent.

[Epaminaidos]

Handbrake with x265 has no problem using nearly 100 percent of my quad core CPU (5 i2500K).

This processor does not support hyperthreading. This might make a difference when comparing CPU usage.

You have a bottleneck somewhere -- reading the source or filtering.

The hdd does not seem to be the issue, since it is idling most of the time. The only filter I use is deblocking (which should use even more CPU per frame I guess).

95 degrees C is very high, especially with only 50 percent CPU usage. You should look into better cooling. My i5 only goes a little above 50C when encoding at 100 percent.

Do you use a notebook or a desktop?

[jagabo]

Handbrake with x265 has no problem using nearly 100 percent of my quad core CPU (5 i2500K).

This processor does not support hyperthreading. This might make a difference when comparing CPU usage.

It might. But I'm pretty sure x265 can come close to 100 percent on a 4 core+hyperthreading CPU if it's given frames fast enough.

You have a bottleneck somewhere -- reading the source or filtering.

The hdd does not seem to be the issue, since it is idling most of the time. The only filter I use is deblocking (which should use even more CPU per frame I guess).

Not necessarily. If the deblocking was single threaded and slow it would become a bottleneck. Say for example the deblocking was singled threaded and took 1 hour per frame. x265 would only be given one frame per hour to compress. It would spend most of its time just waiting for the next frame. And since the deblocking was only using one thread you would see ~12.5 percent CPU usage. On very fast computers decompression of the source video often becomes the limiting factor.

95 degrees C is very high, especially with only 50 percent CPU usage. You should look into better cooling. My i5 only goes a little above 50C when encoding at 100 percent.

Do you use a notebook or a desktop?

I use a desktop. Though it's optimized more for quiet running than for low temps. Most laptops have insufficient cooling to run the CPU at 100 percent for extended periods.