Battery Power for xu4?

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Re: Battery Power for xu4?

Unread postby memeka » Sun Mar 26, 2017 8:29 pm

Using the HW encoder you can reduce CPU usage a lot. You can probably get 1080p resolution with less CPU usage.
Capping big cores at 1.6 would greatly increase battery life. Power usage is not linear e.g. From 1.8Ghz to 2Ghz you get 10% speed increase but >20% power usage, made worse by higher temps as cooling will also use power.
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Re: Battery Power for xu4?

Unread postby cdhinrichs » Mon Mar 27, 2017 7:33 am

Thanks, mad_ady.

I didn't know that about the 1st 4 cores vs the last 4. Maybe I can set those to "performance" and leave the last 4 as "conservsative". I like the idea of writing it up as a project, but I'm still developing the concept. If the point were to record video, I'd be mostly done, and in that case your suggestion to use hardware encoding is a good one. But what I really want is to try to do some real-time computer vision stuff, which needs raw frames. The purpose of doing software H.264 is really to see how much I can push the CPUs while on battery. And, I think I can push them a little further.

I didn't know about the "MFC" encoder / decoder hardware. The words "encode" and "decode" do not occur anywhere in the XU4 user manual. Neither does "MFC", but there is a word about an "XMBC". If I can get a camera to stream H.264, and then decode raw frames in hardware, then that would expand my range of choices for cameras - a lot of the "GoPrO" style outdoor cameras that have wider FOV and HDR rely on onboard H.264 encoding - you can either download the video later, or it can stream H.264, but no raw frames.

Running specific jobs on specific CPUs is good info, thanks.
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Re: Battery Power for xu4?

Unread postby cdhinrichs » Mon Mar 27, 2017 10:50 am

Hi memeka,

With my setup, I have about 75 Amp-hours of battery, so at the rated 5A for the odroid, that's 15 hours, and even at 7.5A that's still 10 hours. The difficulty really has been getting a sufficient amp draw, and controlling the ramp-up so that the batteries could cope with it.

But, I didn't know about the hardware encoder, which is very valuable to know since even once I go ahead with my computer vision project, it would still be great to have a way to save the outputs.
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