The effect of FPS on image quality ...

[Submariner Gold]

OK I openly confess to zero knowledge about video. Yes I own a professional camera 54MPS so sort of understand resolution etc.

In considering a second rear (stand alone camera) I noticed quite a few cameras “pixelated” ( looks like digitsl blocking) very badly. To my untrained eye when comparing cameras of the same resolution it looked like if they were 1080p at 30 fps, they looked bad as the car speeded up. Whereas 1080p at 60 fps seemed to cope with this a lot better.

Obviously the sensor and processor could have a huge effect on any comparison, but is my guessed assesment correct at least in theory..

I cant really check on my Vico MF3 as this has a funny HDR system at 1,440p that merges 60fps and 30 fps together to give you a consolidated “HDR 30 fps” video file.

Just interested if my assessment was correct, and therefore what to look out for in the other camera, especially as I was thinking of going for a budget camera, That had a good set of reviews.

 

[kamkar]

The pixilation or blocking you will often see when there are a lot going on in the frame, my favorite test place was a place where trees lined the road and so thin time of the year with a low sun filtering thru the trees and casting shadows on the road make just about any camera fold as the bitrates cant really keep up with that much information.
If you see that effect while stopped or parked then there is something wrong for sure, but that's not really a problem but some handle movement and lot of information better than others, even with same bitrate and file container.

When it come to youtube i have often suspected they favor some camera brands over other, but its hard to prove just something i feel.
But it is strange you can have a pretty good 1080p recording that look really good, then upload it to youtube and then they kill it with their trans-coding of it, really strange i think, i can sort of get it if the video you upload have some problems and then youtube amplify those too, but i dont feel that's the case many times.
And if you take the same video and upscale it to 4K before you upload it, then suddenly the problems are gone on the youtube copy.

Just look at these 2 videos, one is the original 1080/60 video 40 mbit, the other are the same video just up-scaled to 4K 40mbit in pinnacle studio 20 ultimate
And its not like a lot go on in the videos, and the original file also looked just fine on my computer.

 

[jokiin]

I noticed quite a few cameras “pixelated” ( looks like digitsl blocking) very badly.

this generally relates to low bitrate rather than frame rate

 

[Submariner Gold]

this generally relates to low bitrate rather than frame rate

Hmmm not many Dashcam specs seem to publish the bitrate? So how do you assess a camera? (Other than buy it, and then look at the file it produces on a video editor?, which is by then too late!)
E.g. my camera boasts about a 4MPS sensor, 1440p [2560x1440p @30fps HDR]; ultra high dynamic range, and 3D NR, but like many other dashcams, it doesnt states the actual bitrate.

 

[jokiin]

Most brands don't list this detail, they probably think it's unnecessary, or perhaps not understood by most end users

 

[Submariner Gold]

Most brands don't list this detail, they probably think it's unnecessary, or perhaps not understood by most end users

So one would have to look for a review done by someone with brains!

 

[jokiin]

Another benefit of raw video files, you can assess this yourself

 

[Dashmellow]

Hmmm not many Dashcam specs seem to publish the bitrate? So how do you assess a camera? (Other than buy it, and then look at the file it produces on a video editor?, which is by then too late!)
E.g. my camera boasts about a 4MPS sensor, 1440p [2560x1440p @30fps HDR]; ultra high dynamic range, and 3D NR, but like many other dashcams, it doesnt states the actual bitrate.

As @jokiin mentions you can assess the bit rate of your files yourself. Virtually every media player offers a menu option to view the media statistics of the video you are watching which includes the bit rate and other key info. In this example, from Quicktime Player on a Mac one selects "Show Movie Inspector" from the menu. The data rate is 18.21 Mbits/second. On VLC one would select "Media Information". Give it a try on whatever software you use.



Quicktime Player


VLC

 

[kamkar]

Or just right click on the video file and select properties / details.
But it seem to me most dashcams hover around 18 - 20 mbit.
I have experimented with modified firmwares and used 30 - 40 mbit and that was nice in this regard, but then your file size also grow to double size, so it seem here like in politics its a matter of choosing between plague and cholera.

 

[Nigel]

A lot of cameras that have a 60fps mode record the 60fps with a higher bitrate than the 30fps and the higher bitrate means less pixilation. For dashcam video 60fps really has no advantage other than if the manufacturer provides a higher bitrate.

Some processors do a better job of avoiding pixilation during compression than others, but if there is a huge amount of detail and movement in the image then for a dashcam it is often more important to record the details than to worry about a bit of pixilation in the background. If you want to make cinema quality video then a dashcam is not the right choice of camera. If you want to collect evidence then the pixilation doesn't matter, the pixel perfect licence plates do.

 

[Matt_V939]

So one would have to look for a review done by someone with brains!

You have to look at those reviewers which puts camera on fpv quadcopters....(of course they won't review dedicated dashcams, but mobius/F1 style ones).
They are having pretty rough conditions (grass/foliage/sudden exposure change).

 

[Submariner Gold]

Thanks guys, yes I appreciate I can quite easily review the files my current camera makes and see the bitrate.

Its the process of evaluation / buying a second camera, where I dont have access to the raw files of possible purchase options that casue the problem. Ideally I would like to know which ones have a high bitrate. Very few manufacturers publicise this statistic, and a lot of reviews dont touch on it.

I concur with Nigel’s statement, that a dashcam isnt designed to produce travel log style videos. But, I just wish these stats were published; because if I had a shortlist of 2 (where admittedly both might do the job) I would prefer to buy the one that pixelated the least amount.
I also think, were such a file ever needed to underpin ones innocence; viewing a clear video of say the run up to a crash might be more “convincing” if it looked professional and very clear.
A question of perception ....
And if they are of a similar price, why not go for the clearer image resolution?

 

[Paul Iddon]

Nice horse @kamkar1

 

[Paul Iddon]

Here are 5 images showing the bit rate on my 5 dashcams. The 612 is a 4K camera but the first shot was at 2K, the B1W Conbrov, and Oumax are 1080 and the Z-Edge is 2K. The last one is from the 612 4K running at 4K resolution.. I must say too, that at different parts of the video, the bit rate figures varied quite a lot, and I think these are examples of the better moments.

Odd that the Oumax reported back such a low number...

 

[Module 79L]

Its the process of evaluation / buying a second camera, where I dont have access to the raw files of possible purchase options that casue the problem. Ideally I would like to know which ones have a high bitrate. Very few manufacturers publicise this statistic, and a lot of reviews dont touch on it.

Unless it's a relatively unknown or not very common camera, you'll most likely find that information here on DCT.

 

[Submariner Gold]

Here are 5 images showing the bit rate on my 5 dashcams. The 612 is a 4K camera but the first shot was at 2K, the B1W Conbrov, and Oumax are 1080 and the Z-Edge is 2K. The last one is from the 612 4K running at 4K resolution.. I must say too, that at different parts of the video, the bit rate figures varied quite a lot, and I think these are examples of the better moments.

Odd that the Oumax reported back such a low number...

View attachment 36133View attachment 36134View attachment 36135View attachment 36136View attachment 36137

Thanks for the time taken to do this.
Wierdly for dash cam puposes shot 2 looked the cleanest.
I was also surprised how disapointing the 612 at 2K and especially at 4K were.

 

[TonyM]

Unless it's a relatively unknown or not very common camera, you'll most likely find that information here on DCT.

Agreed. The better reviewers here on DCT will include bitrates in their DC reviews, and/or provide RAW sample video clips for you to view yourself.