Undervolting drastically improves 4K video recording?

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Pesetio

Senior Member
May 7, 2014
61
28
I've been fooling around with undervolting CPU frequencies for the past few weeks and I've noticed that it improves 4K video recording remarkably.
.402 firmware has something to do with it too since 4K video has been underclock to 800mhz rather then 1ghz on previous firmwares.

As you can see from the sceenies below I got 34mins of 4K which was about a 13GB file. Phone was also not very hot, I would say very warm.

RNqHUQn.png
9UYNjLl.png


I can't remeber how much I undervolted from default, so I've uploaded some screenshots of my undervolts below

cT615Oc.png
EqcXRp9.png
u5XegFZ.png


*NOTE* that the important frequency to undervolt would be 800mhz since that is frequency it is locked at while using 4K video recording on .402 firmware. .69 firmware and lower would lock the frequencies at 1ghz so you would undervolt the 1ghz frequency.

I cannot confirm all this as I'm the only one I know that has tested it. I will need others to try and see if they get better results then they had previously, you don't need to get 30mins for good results. I just want to know if it improves 4K for you guys or if its still the same.

*NOTE* not all phones are made the same, some phone might not be able to undervolt as much as others and may cause your phone to slowdown or reboot.

*UPDATE* did some more tests to see the temperature and if I could do back to back recordings, these were the results

36mins >>
qyEccgQ.png
30mins >>
0ODq3iK.png


As you can see from the time difference in the screenshots there was less then 1min difference, this is because I went into system monitor to check the temperature before I started the next recording. Max temp was 44c and the current temp was 42c. Seems like I could do back to back recordings endlessly, the reason I didn't do more was because I had low battery at the time and 66mins of 4K recording drained about 45% or more of my battery.

*NOTE* Weather plays an important factor and it is winter here, my first recording was done @ 11C, the 2nd and 3rd ones where done @ 16c
 
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Pesetio

Senior Member
May 7, 2014
61
28
I can conform it as it's logical, the camera shuts down due to overheating so less voltage means less heat obviously :)

Sent from my D6503 using Tapatalk

:) Yeah, I understand it's logical and I was referring to the drastic impact it seemed to have for me. I haven't really noticed anyone confirming that 4K video is better on .402 since it should be because 4K is underclock from 1ghz to 800mhz.
 
Last edited:

Mr.R™

Senior Member
Aug 11, 2008
899
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OnePlus 8 Pro
Sony Xperia 5 II
Would be good to test the temperature differences really, see how far it is below the threshold once undervolted, I'm - 36 on all steps so I may test later busy with kids atm tho

Sent from my D6503 using Tapatalk
 

Rilavalon

New member
Apr 15, 2011
3
0
I've been fooling around with undervolting CPU frequencies for the past few weeks and I've noticed that it improves 4K video recording remarkably.
.402 firmware has something to do with it too since 4K video has been underclock to 800mhz rather then 1ghz on previous firmwares.

As you can see from the sceenies below I got 34mins of 4K which was about a 13GB file. Phone was also not very hot, I would say very warm.

[...]

*NOTE* that the important frequency to undervolt would be 800mhz since that is frequency it is locked at while using 4K video recording on .402 firmware. .69 firmware and lower would lock the frequencies at 1ghz so you would undervolt the 1ghz frequency.

I cannot confirm all this as I'm the only one I know that has tested it. I will need others to try and see if they get better results then they had previously, you don't need to get 30mins for good results. I just want to know if it improves 4K for you guys or if its still the same.

*NOTE* not all phones are made the same, some phone might not be able to undervolt as much as others and may cause your phone to slowdown or reboot.

It seems to be a good point. Does the bitrate remain the same when you are undervolting & underclocking your XZ2 ?
I don't know if the cpu is used for 4K encoding or if it's a special processing unit.
We can't lock the cpu frequencies without root ...
Sony should lock cpu power when the camera application is used because 1080p @60fps and numerous shot at 20.7mpix turn it into oven.:crying:
 

pepeo123

Senior Member
Aug 30, 2013
79
22
yeah it makes complete sense. the chipset will be using less voltage and current, wich means less power. less power = less heat

in my desktop core i7 4770k for example, if i undervolt 120mv from the original voltage, i can get like 13C diference in temperatures
 

Pesetio

Senior Member
May 7, 2014
61
28
It seems to be a good point. Does the bitrate remain the same when you are undervolting & underclocking your XZ2 ?
I don't know if the cpu is used for 4K encoding or if it's a special processing unit.
We can't lock the cpu frequencies without root ...
Sony should lock cpu power when the camera application is used because 1080p @60fps and numerous shot at 20.7mpix turn it into oven.:crying:

The CPU basically has 100% usage on all 4 cores when it's recording in 4K, I'm not sure about the GPU but when I have underclocked the GPU to 200MHz, after 4K video recording it defaults back to the 575Mhz.

Which app do you use to undervolt your phone? :)

You need to have doomkernel 6 or above installed. If you have Romaur, it comes with a default app (Performance Control). You can use Fauxclock, SetCPU etc..
 

Pesetio

Senior Member
May 7, 2014
61
28
have you done any stress testing ?

How is the stability. This will take time to assess.

Not really however it was getting a stress test @ 800Mhz frequency, since 4K recording stresses the CPU and that is for over 30mins and I have had now slowdowns, glitches or reboots since my undervolts.
 

Pesetio

Senior Member
May 7, 2014
61
28
Do you recall the surrounding ambient temperature under which you got this performance ?

11c

However I did another test that was done at 16c where I got 36mins, checked the CPU temperature, max 44c, current 42c then I went straight into 4K again and to my surprise I got 30mins.
44c must be the cutoff temperature, what was surprising is that from 42c to 44c took my phone half an hour of 4K recording to reach.

Seems like I could keep doing 30+ mins of 4K endlessly. Obvious battery goes down hard, 66mins of 4K was 45% battery drain.

It's winter here in Melbourne now so obviously that plays an important factor. I'll have to edit original post to include these factors so it doesn't mislead people.
 

pvyParts

Inactive Recognized Developer
Oct 11, 2010
1,858
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* note

every CPU is slightly different some can handle more undervolt than others ( much like an overclock ) :) so YMMV with how far you can push the UV.

and hiyo from the west coast (perth) @One Twelve

pvy.
 

One Twelve

Senior Member
Oct 28, 2013
2,619
640
11c

However I did another test that was done at 16c where I got 36mins, checked the CPU temperature, max 44c, current 42c then I went straight into 4K again and to my surprise I got 30mins.
44c must be the cutoff temperature, what was surprising is that from 42c to 44c took my phone half an hour of 4K recording to reach.

Seems like I could keep doing 30+ mins of 4K endlessly. Obvious battery goes down hard, 66mins of 4K was 45% battery drain.
oh no, i was so hoping it was warmer when you did that test.

11c or 16 c is 20 degrees lower than where i am.

What this means is the Z2 will at least be able to match the rest unlike presently when it comes to heating.

Stabilisation causes faster heating because its resource intensive. Z2 matched the lumia 920 which is some feat but it won't be able to record for as long unless ambient temperatures are 10-20 degrees. At those temps camera works longer by a significant margin over stock. Even at elevated ambient temperatures I expect there will still be an improvement. P =V^2/R and all.

The next question i have is by how much is cpu performance affected say in benchmarks as a result of under volting ?

It's winter here in Melbourne now so obviously that plays an important factor. I'll have to edit original post to include these factors so it doesn't mislead people.
yes, would make things more clear.
 
Last edited:

Pesetio

Senior Member
May 7, 2014
61
28
Stabilisation causes faster heating because its resource intensive.

I was curious so I did another test, I enabled and disabled and didn't really notice any difference in CPU usage however when I did the test I noticed that the CPU cores are clocked @ 1.2ghz now but uses less CPU. Higher clock with less CPU usage seems to be better then lower clock with more CPU usage.
I have been on Romaur 3.0 which is also .402 and it was locked @866mhz and all the CPU cores were at 98 - 100 usage. Very strange indeed.

I have noticed some strange things though from prevous versions, such as being able to under or overclock each individual CPU core and have the settings always stick which I could not do before. Maybe it's because I updated to Doomkernel 9 but I'm not sure.

Have you got the system monitor app with the floating notifcation? I'd like to know what your 4K video is running @ and what kind of CPU usage u get.

I'm on Romaur 3.1 and Doomkernel 9
 

One Twelve

Senior Member
Oct 28, 2013
2,619
640
Pesetio, i don't have a Z2 yet. But am watching developments on it. Your work here is very promising :victory:
 

Pesetio

Senior Member
May 7, 2014
61
28
Pesetio, i don't have a Z2 yet. But am watching developments on it. Your work here is very promising :victory:

Ahh ok I thought you had one lol :)

You'll enjoy it when you do though

For others who do have the phone it would be interesting to know the CPU frequency that you 4K records in and what the CPU usages are, might be able to pinpoint the problems with 4K recording.

The only program I know of that has floating notification is System Monitor (paid version), I'm sure there is a free program that does this though I'm not sure myself.

aX01OMF.png
 
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progressfx

Senior Member
Apr 3, 2011
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had that issue.i have underclocked my CPU to 1.7 per core. after that i filmed 15 minute file, rec was stopped beacause my sd is full.
 

Pesetio

Senior Member
May 7, 2014
61
28
had that issue.i have underclocked my CPU to 1.7 per core. after that i filmed 15 minute file, rec was stopped beacause my sd is full.

Good to see that it worked for you, I think undervolting plays a part but the CPU usage when recording 4K plays a major part, if you get very high CPU usage your phone will heat up very quickly and you won't get long recordings, however if you get low CPU usage (even @ high frequencies) you will get very long video recordings and phone will not be too hot.



I saw your post, it's actually better to record to the internal storage because it's apparently faster, however all of my tests were conducted onto the externalSD.

I did some more tests, this time I turned on my heater to try to recreate a hot climate lol.

I had the phone running @ 1.6ghz with the floating CPU notification on top and heater blowing hot air (1 notch down from max) from about a meter away. The CPU usage was quite low, so I immediately new that the recording would go on for at least 30mins which is did. Phone didn't feel any hotter then usual. And like usual I could go on and record 4K again straight after for 30+mins.

I'm confident to say that it is the CPU usage that is the main culprit. High CPU usage @ lower frequency will not get a long recording compared to low CPU usage @ higher frequency.

Just check the CPU usage when recording 4K and you will know right away if you are going to get good or bad results.

I know there is a mod that increases the heat threshold but personally I wouldn't use it since the threshold is there for a reason.
 
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  • 7
    I've been fooling around with undervolting CPU frequencies for the past few weeks and I've noticed that it improves 4K video recording remarkably.
    .402 firmware has something to do with it too since 4K video has been underclock to 800mhz rather then 1ghz on previous firmwares.

    As you can see from the sceenies below I got 34mins of 4K which was about a 13GB file. Phone was also not very hot, I would say very warm.

    RNqHUQn.png
    9UYNjLl.png


    I can't remeber how much I undervolted from default, so I've uploaded some screenshots of my undervolts below

    cT615Oc.png
    EqcXRp9.png
    u5XegFZ.png


    *NOTE* that the important frequency to undervolt would be 800mhz since that is frequency it is locked at while using 4K video recording on .402 firmware. .69 firmware and lower would lock the frequencies at 1ghz so you would undervolt the 1ghz frequency.

    I cannot confirm all this as I'm the only one I know that has tested it. I will need others to try and see if they get better results then they had previously, you don't need to get 30mins for good results. I just want to know if it improves 4K for you guys or if its still the same.

    *NOTE* not all phones are made the same, some phone might not be able to undervolt as much as others and may cause your phone to slowdown or reboot.

    *UPDATE* did some more tests to see the temperature and if I could do back to back recordings, these were the results

    36mins >>
    qyEccgQ.png
    30mins >>
    0ODq3iK.png


    As you can see from the time difference in the screenshots there was less then 1min difference, this is because I went into system monitor to check the temperature before I started the next recording. Max temp was 44c and the current temp was 42c. Seems like I could do back to back recordings endlessly, the reason I didn't do more was because I had low battery at the time and 66mins of 4K recording drained about 45% or more of my battery.

    *NOTE* Weather plays an important factor and it is winter here, my first recording was done @ 11C, the 2nd and 3rd ones where done @ 16c
    2
    It seems to be a good point. Does the bitrate remain the same when you are undervolting & underclocking your XZ2 ?
    I don't know if the cpu is used for 4K encoding or if it's a special processing unit.
    We can't lock the cpu frequencies without root ...
    Sony should lock cpu power when the camera application is used because 1080p @60fps and numerous shot at 20.7mpix turn it into oven.:crying:

    The CPU basically has 100% usage on all 4 cores when it's recording in 4K, I'm not sure about the GPU but when I have underclocked the GPU to 200MHz, after 4K video recording it defaults back to the 575Mhz.

    Which app do you use to undervolt your phone? :)

    You need to have doomkernel 6 or above installed. If you have Romaur, it comes with a default app (Performance Control). You can use Fauxclock, SetCPU etc..
    1
    Pesetio, i don't have a Z2 yet. But am watching developments on it. Your work here is very promising :victory:

    Ahh ok I thought you had one lol :)

    You'll enjoy it when you do though

    For others who do have the phone it would be interesting to know the CPU frequency that you 4K records in and what the CPU usages are, might be able to pinpoint the problems with 4K recording.

    The only program I know of that has floating notification is System Monitor (paid version), I'm sure there is a free program that does this though I'm not sure myself.

    aX01OMF.png
    1
    had that issue.i have underclocked my CPU to 1.7 per core. after that i filmed 15 minute file, rec was stopped beacause my sd is full.

    Good to see that it worked for you, I think undervolting plays a part but the CPU usage when recording 4K plays a major part, if you get very high CPU usage your phone will heat up very quickly and you won't get long recordings, however if you get low CPU usage (even @ high frequencies) you will get very long video recordings and phone will not be too hot.



    I saw your post, it's actually better to record to the internal storage because it's apparently faster, however all of my tests were conducted onto the externalSD.

    I did some more tests, this time I turned on my heater to try to recreate a hot climate lol.

    I had the phone running @ 1.6ghz with the floating CPU notification on top and heater blowing hot air (1 notch down from max) from about a meter away. The CPU usage was quite low, so I immediately new that the recording would go on for at least 30mins which is did. Phone didn't feel any hotter then usual. And like usual I could go on and record 4K again straight after for 30+mins.

    I'm confident to say that it is the CPU usage that is the main culprit. High CPU usage @ lower frequency will not get a long recording compared to low CPU usage @ higher frequency.

    Just check the CPU usage when recording 4K and you will know right away if you are going to get good or bad results.

    I know there is a mod that increases the heat threshold but personally I wouldn't use it since the threshold is there for a reason.
    1
    On mine (.402 TW, stock, non rooted) with steady shot on, in 4K the load goes up between 60-90% on 3 cores an 1 core is at 30-40%, clock speed at 800.
    If I turn steady shot off, load goes down to 50-60% on 3 cores and under 30% in the last one (actually this is the first core as shown by the app) with clock speed goind down sometimes in one or two cores to 300, 400, 600 (or even off in one core).

    Reading the last posts (higher clock vs load) I'm confused. Do you say that the way it was on .69 was better? I mean keeping it at 1 Ghz is better than 833 Mhz (because the load is lower on 1 Ghz)?

    How long can you record for?

    When I tested 4K a few weeks ago, I noticed that the CPU usage was 90-100% and locked at 883 @ all cores but now that I get less CPU usage, the phone can record much longer. I also can't explain why it doesn't use much CPU usage now compared to before.

    Yes, steady-shot seems to stress the CPU more, 1. Core 30% load all others up to 80%

    I think sony knows wich clockstep and wich voltage is the most efficient to use while recording 4K, but I don't really understand why the phones heats up so much during 4k recording, 4 Core Load on 2.3 GHz should be a problem but not on 883 MHz.

    But now we know sony can improve it a lot by tweaking the kernel.