A139 Pro Road Trip - to HDR or not to HDR?

[Nigel]

I was driving up into the hills on a nice sunny day, with great views, and I thought... I will keep this video.
Then I thought, it is on Auto HDR, which will mean HDR is off ... Do I want HDR On for a driving video?
So I recorded the first half of the trip with HDR still on Auto, thus Off, and the second half with HDR On:
(I suggest using Google Chrome if you want to properly see the HDR content in these videos, or if you are on an iPhone then switch to the Youtube app, but other options may work!)

And here is the return trip, on a not so sunny day, with HDR On and EV -1:

To complicate things, I uploaded the HDR On videos to Youtube as HDR format videos. The A139 Pro, for compatibility reasons, outputs SDR format video files for both HDR On and HDR Off, so they need a little conversion before uploading to Youtube in real HDR format. To complicate things even more, if you are watching on a TV/Computer/Phone that does not have an HDR display then you won't be able to see them in HDR format and Youtube will have converted them back to SDR for you, the result may not be quite the same as the original. How do you know if you are seeing them in HDR format? Well it should be obvious, but if you check the resolution on the Youtube Settings cog then you will see HDR written against the resolution, and the cog itself will have a red HDR logo in place of the normal red HD logo. If you think that you don't have an HDR display, remember that many iPhones do, they are quite common and work well.

So, is A139 Pro driving video better with HDR On, or HDR Off?
And is anyone achieving better results somehow?

I am having a few issues with over exposure in the sky with both HDR On and HDR Off, but slightly worse with HDR On, also the dark areas seem to get even darker with HDR On, so it seems there is too much contrast with HDR On. The whole idea of HDR is that it has a larger dynamic range, so there ought to be less contrast, not more! When used as an accident camera, the HDR is working and does help, but maybe we could do with separate exposure settings for road trips and accident recording?

Because of the over exposed sky, I set EV -1 for the return trip (third video above), which does darken the video as expected, but doesn't appear to solve the over exposed sky issue, and also appears to increase saturation, I don't think it is an improvement. I also tried EV -2, still without solving the sky issue, but then most of the image became too dark. Part of the issue with the sky is the conversion from fake HDR to real HDR which is making the over exposed sky look worse, but it is only having a problem because of the over exposure, not causing it. Maybe it is possible to improve the conversion though?

I was going to embed an HDR frame grab here, but having saved the frame as an HDR image file, I can't find anywhere to host the HDR image which will allow me to embed it here - so many things still do not work with real HDR! The best I can do is a google drive download link, but then most people will have problems viewing it, while if something would allow me to embed it here then there would be no problem, well, as long as people are using a browser that supports HDR, on a device with an HDR display!

HDR Lake.avif

drive.google.com

HDR Sky Road.avif

drive.google.com

Having downloaded those two HDR image files, best way to view them appears to be to open them in Google Chrome, about the only way to see the HDR correctly! It is a good thing that the A139 Pro doesn't write its HDR video to real HDR files! Although it would be good to have an option in the settings for true 10 bit HDR video, in true 10 bit HDR video files with no over exposed clouds in the sky, even if only for people who want to make road trip movies...

Someday real HDR will be the norm, and everything will support it, but we are still a long way from that, and we have to make do with SDR:

 

[kamkar]

We Danes only had something like that, when we threw our weight around over there.
Now we are just sad.

 

[Nigel]

We Danes only had something like that, when we threw our weight around over there.
Now we are just sad.

You mean that Denmark is 2 dimensional?

There are probably some 3 dimensional bends in Greenland... but then they don't have many roads...

 

[Panzer Platform]

How do you know if you are seeing them in HDR format? Well it should be obvious, but if you check the resolution on the Youtube Settings cog then you will see HDR written against the resolution, and the cog itself will have a red HDR logo in place of the normal red HD logo.

Can you post a screenshot of the HDR logo in the YouTube cog menu?
I can definitely see the difference in the videos on my screens, but I don’t see the HDR logo you’re taking about when I adjust the resolution / quality settings in the YouTube player on my Chromebook, or iPhone.

Thanks for posting this.
This confirms my “belief” that;
1.) Current HDR should only be used at night time & low light situations.
2.) Current HDR should not be used during the daytime.
Is that wrong?
-Chuck

 

[Nigel]

Can you post a screenshot of the HDR logo in the YouTube cog menu?

Apparently not!

However, from the iPhone, I can post a screenshot of “HDR” instead of “HD” on the quality menu:


Note: Viewing the HDR video on the iPhone in the chrome browser did not give HDR, pressing the YouTube icon to switch to the YouTube app does show a beautiful bright sunny day, and from there I got the above screenshot…

 

[Nigel]

2.) Current HDR should not be used during the daytime.

Seems to depend on what you are viewing on, my PC does not have HDR and I think is best with HDR off, although HDR on but viewed in SDR file format is different rather than worse. On a MacBook, I prefer the HDR, but it is not brilliant, and on the iPhone, in the YouTube app, it is literally a brilliant sunny day, which I much prefer…

 

[Nigel]

Interestingly, the sky over exposure issue is much better on the iPhone than on the MacBook Pro, maybe it is more the MacBook that is the problem, although the brightest areas of sky are definitely over exposed at times.

 

[JardaB]

Over exposed sky is not problem for dashcam. HDR tends to be better at night, but you need to test how it reads the car's license plate

 

[Nigel]

Over exposed sky is not problem for dashcam. HDR tends to be better at night, but you need to test how it reads the car's license plate

For recording accidents, I agree, in fact it is best to have the sky a little over exposed so that the rest of the image has more detail, but if you are making a movie then you don't want the clouds over exposed, thus I suggest we need a "Movie" setting in the menu.

 

[JardaB]

No problem .. in the settings there is a menu to correct the exposure of each one camera (front/rear/inside) +- EV

 

[Vortex Radar]

Wow, gorgeous scenery! Good tips about the HDR quality options in YouTube. I just watched it on two screens at once, one with HDR and one without, and the difference was pretty striking. The HDR one had better colors (which may just be the color calibration of the devices), but the additional cloud detail was pretty noticeable, as expected.

I always figured that for pretty scenic stuff like this, HDR would be the way to go when possible. That would outweigh any potential ghosting artifacts from the double exposure since users would likely be sitting back to take in the whole view instead of pausing and pixel peeping tiny details like license plates, heh.

I see what you mean too regarding HDR having more contrast than SDR.

 

[Nigel]

and the difference was pretty striking.

Ahh, one person has seen the light . Now you understand real HDR!

I suspect most people can't see it
And even for those that can, there is another striking difference between a proper 1000 nit HDR screen and feeble 500 nit semi-HDR devices that seem to be quite popular at the moment, even this MacBook Pro is only half HDR!

I always figured that for pretty scenic stuff like this, HDR would be the way to go when possible. That would outweigh any potential ghosting artifacts from the double exposure since users would likely be sitting back to take in the whole view instead of pausing and pixel peeping tiny details like license plates, heh.

Yes, a little blur/ghosting tends to improve movies, movie makers always want slow exposure times of only around 1/60th second so that movement between frames looks smooth.

Wow, gorgeous scenery!

Sort of normal around here, only 8 minutes from home, but it doesn't often have the sunshine and clear visibility!

 

[Vortex Radar]

If you don't mind me asking, what editor did you use for working with HDR and SDR clips? I've been working on an SDR timeline in FinalCut all this time and had been (perhaps incorrectly) assuming all the HDR clips were automatically being compressed to SDR in-camera. I'm researching now how to work with HDR footage in FinalCut, how to mix HDR and SDR footage on the same timeline, and what settings to select when colorgrading to get the SDR footage to look accurate when dropping into an HDR timeline.

When I load some Viofo HDR footage into FinalCut, it's still showing up as Rec 709 instead of Rec 2020 so I'm not totally sure if it's being recognized as HDR footage in the first place.

I'd like to have HDR footage show up as such when being displayed on HDR-capable displays, but would that cause any brightness inaccuracies when people watch HDR videos on an SDR display?

It is a good thing that the A139 Pro doesn't write its HDR video to real HDR files! Although it would be good to have an option in the settings for true 10 bit HDR video, in true 10 bit HDR video files with no over exposed clouds in the sky, even if only for people who want to make road trip movies...

Wait, so you're saying the HDR video it shoots is being converted down to 8-bit SDR? That's what I was thinking too. That said, how exactly are you telling YouTube that you're working with an HDR clip? Does YouTube render the HDR clip differently if you upload it as if it's an SDR clip?

 

[Nigel]

If you don't mind me asking, what editor did you use for working with HDR and SDR clips?

#Technical section!

Those clips in post #1 are not actually edited, just converted. Last time I looked at editors for HDR, most free/cheap editors did not support HDR output at all and even the professional ones seemed to have lots of problems. Things ought to be improving now, but I suspect there are still a lot of problems, there are enough problems just displaying HDR! I don't know FinalCut, so can't help much with that.

As you point out, all current Viofo cameras output 8 bit video marked as Rec 709 colourspace, however the contents are not really Rec 709, it is mis-marked, which is very useful for compatibility with the "old" software everyone is using to display/edit it, but when displayed on any display looks very low contrast with poor colour saturation. It does not look realistic in contrast or colour.

What I have done with the above clips is to use ffmpeg to concatenate the loop recording segments into a single file, eg the last clip is 13 one minute files concatenated into a single file without recompression, which makes it much easier to work with.

Then I have used ffmpeg again to recompress the single file as H265 HDR10, converting the Rec 709 colourspace into Rec 2020 colourspace. I'm not sure I fully understand the ffmpeg colourspace conversion controls, but essentially it is just a linear mapping of the 8bit to 10bit, a multiplication of x4, not using any of the normal colour conversion profiles, since the data is just marked wrong for Rec 2020 rather than being wrong. In reality it is still not well calibrated since Viofo are trying to store detail rather than get colour accuracy, they are not using a normal gamma curve, it is modified by WDR and maybe more, but it is close enough for a linear conversion profile to produce nice results. Important to note that the original file uses full range 8 bit colour (0-255), not the restricted TV range. I was also turning the colour saturation down a bit, but that only seemed to be necessary for some displays, so I removed it from the above clips, seems to be important what display type you are targeting, the parameters for which get embedded in the output.

Wait, so you're saying the HDR video it shoots is being converted down to 8-bit SDR? That's what I was thinking too. That said, how exactly are you telling YouTube that you're working with an HDR clip? Does YouTube render the HDR clip differently if you upload it as if it's an SDR clip?

No, it is not really being converted to SDR, just stored in a file marked as SDR Rec 709, it still has an HDR profile, which you can assume to be more or less Rec. 2020.

To upload HDR to Youtube, as far as I know, it only accepts HDR10 Rec 2020 files, anything else it may accept, but it will never put the HDR option up, just standard SDR viewing options. I've been using H265 files, although I'm pretty sure it accepts VP9 and AV1 HDR files.

Hope some of that helps! Ask if you want the ffmpeg command, or I can convert a file for you so that you can test if it works with your FinalCut system...

 

[Vortex Radar]

As you point out, all current Viofo cameras output 8 bit video marked as Rec 709 colourspace, however the contents are not really Rec 709, it is mis-marked, which is very useful for compatibility with the "old" software everyone is using to display/edit it, but when displayed on any display looks very low contrast with poor colour saturation. It does not look realistic in contrast or colour.

lol interesting...

From a review perspective, as nice as it'd be to show people all the extra dynamic range available in HDR, if it's not going to be available for people when they copy the video file to their computer and load it into a video player, I wonder if any conversion would be misleading given that it wouldn't be representative of what people would see on their end.

What I have done with the above clips is to use ffmpeg to concatenate the loop recording segments into a single file, eg the last clip is 13 one minute files concatenated into a single file without recompression, which makes it much easier to work with.

Then I have used ffmpeg again to recompress the single file as H265 HDR10, converting the Rec 709 colourspace into Rec 2020 colourspace. I'm not sure I fully understand the ffmpeg colourspace conversion controls, but essentially it is just a linear mapping of the 8bit to 10bit, a multiplication of x4, not using any of the normal colour conversion profiles, since the data is just marked wrong for Rec 2020 rather than being wrong. In reality it is still not well calibrated since Viofo are trying to store detail rather than get colour accuracy, they are not using a normal gamma curve, it is modified by WDR and maybe more, but it is close enough for a linear conversion profile to produce nice results. Important to note that the original file uses full range 8 bit colour (0-255), not the restricted TV range. I was also turning the colour saturation down a bit, but that only seemed to be necessary for some displays, so I removed it from the above clips, seems to be important what display type you are targeting, the parameters for which get embedded in the output.

This may be a silly question since the whole point of using HDR is to get better dynamic range compared to SDR, but do you feel that your conversion process accurately represents what the dashcam is recording and capturing?

I tend to avoid any color grading, sharpening, shadow or highlight recovery, etc. It may be necessary when working with HDR footage and manually controlling the tone mapping, but again I think we're starting to walk into questions about how the end user is processing the footage vs. how the dashcam is actually capturing the footage.

Sorta similar to people editing RAW photos instead of just posting JPEGs straight out of camera. Same idea with video.

No, it is not really being converted to SDR, just stored in a file marked as SDR Rec 709, it still has an HDR profile, which you can assume to be more or less Rec. 2020.

This seems to vary by camera. I'm working with Rec 2020 HLG in FinalCut and it looks great with the A139 Pro, but the A119 Mini 2's HDR footage looks much unnaturally darker and lower contrast. The A119 Mini is somewhere in between. Exposure looks very contrasty, but the footage looks to be exposing lower and so it's not as bright as the A139 Pro, but it still looks reasonably correct. I wonder if they're being saved differently and so the conversion isn't leading to comparable results.

To upload HDR to Youtube, as far as I know, it only accepts HDR10 Rec 2020 files, anything else it may accept, but it will never put the HDR option up, just standard SDR viewing options. I've been using H265 files, although I'm pretty sure it accepts VP9 and AV1 HDR files.

Google has some details about this here: https://support.google.com/youtube/answer/7126552?hl=en#zippy=,hdr-video-file-encoding

From some of the videos I've been watching so far, H265 seems to be popular. Looks like there are a number of HDR-specific formats you can use.

I guess what I'm wondering is if I go through the trouble of dropping all the HDR footage onto an HDR timeline and the correcting any SDR footage to look correct alongside the HDR footage, will it all look "correct" regardless of if people are watching in HDR or SDR.

 

[Nigel]

I'd like to have HDR footage show up as such when being displayed on HDR-capable displays, but would that cause any brightness inaccuracies when people watch HDR videos on an SDR display?

If you upload HDR footage, Youtube will convert it to SDR for people without HDR displays, or with insufficient bandwidth. If you take SDR, convert it to HDR and then YT converts it back, it never looks quite the same as the original SDR, but it is reasonable. Of course it depends of the colour profile you used for your conversion, which may not match the one YT uses to convert back. If you start off with HDR and YT converts to SDR then it will look a bit disappointing, but then after watching an HDR display, an SDR display is always going to be disappointing, assuming that you were actually using the extra dynamic range, which you don't have to do, but then when YT converts to SDR it is going to do the wrong thing!

 

[Nigel]

I guess what I'm wondering is if I go through the trouble of dropping all the HDR footage onto an HDR timeline and the correcting any SDR footage to look correct alongside the HDR footage, will it all look "correct" regardless of if people are watching in HDR or SDR.

It is a difficult decision, but any edited video is not exactly the same as the original, that is why some people like to be able to upload original files. For most people, they are watching your videos for other reasons than to see exactly what the original video looked like, you zoom in on the number plates to show if they can be read, but it doesn't matter if the zoom is not a perfect zoom, only that people can judge how good the camera's plate capture is. I rarely watch your videos in 4K, so I can't see the original video quality anyway, and I'm sure many people watch your videos on their phones, where some HDR would look good, but they don't have the 4K resolution, or if they do then they can't actually see it!

I think the main issue is that if you show some HDR dashcam video as I have above, then that is what people will expect to get out of the camera, which is not quite true. Yes, the camera is capable of that, what I have above was recorded by the A139 Pro, but someone buying a A139 Pro can not easily view it like that, at least at the moment.

Eventually you will have to move to HDR videos, for most people it makes more difference to the viewing experience than 4K does, no need to rush though.

 

[Vortex Radar]

It is a difficult decision, but any edited video is not exactly the same as the original, that is why some people like to be able to upload original files. For most people, they are watching your videos for other reasons than to see exactly what the original video looked like, you zoom in on the number plates to show if they can be read, but it doesn't matter if the zoom is not a perfect zoom, only that people can judge how good the camera's plate capture is. I rarely watch your videos in 4K, so I can't see the original video quality anyway, and I'm sure many people watch your videos on their phones, where some HDR would look good, but they don't have the 4K resolution, or if they do then they can't actually see it!

Fair point. YouTube adds its own compression so yes, looking at the original is better. For that reason, whenever I do license plate freezeframes, I like to freeze the actual video itself at the same time which helps minimize any compression going on at the same time and improve the quality of what people can see for the license plate freeze frame. You can see those blown up details better even if you're watching on a smaller display or at a lower resolution. Seeing teeny details on a phone's display is always tough enough as it is.

I think the main issue is that if you show some HDR dashcam video as I have above, then that is what people will expect to get out of the camera, which is not quite true. Yes, the camera is capable of that, what I have above was recorded by the A139 Pro, but someone buying a A139 Pro can not easily view it like that, at least at the moment.

Eventually you will have to move to HDR videos, for most people it makes more difference to the viewing experience than 4K does, no need to rush though.

Perhaps if you add some caveats regarding what people are looking at including the processing you have to do to get there and what they'll natively seen straight out of camera, that would help to avoid any dashed expectations regarding what people see and what they'll get.

 

[Nigel]

This may be a silly question since the whole point of using HDR is to get better dynamic range compared to SDR, but do you feel that your conversion process accurately represents what the dashcam is recording and capturing?

Yes, I haven't edited the videos, that is what was recorded, although there may be a better conversion that maps out Viofo's WDR curves.

What I don't really understand is why an HDR display doesn't display SDR video exactly as I have it above? Instead all HDR displays turn down the brightness of SDR video to the brightness of an old fashioned CRT tube display, not even as bright as a typical LCD monitor!

 

[Vortex Radar]

Yes, I haven't edited the videos, that is what was recorded, although there may be a better conversion that maps out Viofo's WDR curves.

When I use the term “editing,” it’s a generic term that applies even to something extremely simple like concatenating multiple files, but I understand how you mean it.

If you’re looking at different ways of converting that leads to the output video looking different in terms of colors, luminance, etc. then the discussion does go beyond semantics.

What I don't really understand is why an HDR display doesn't display SDR video exactly as I have it above? Instead all HDR displays turn down the brightness of SDR video to the brightness of an old fashioned CRT tube display, not even as bright as a typical LCD monitor!

Right which throws a whole wrench into the system regarding sharing footage for people to view that is representative of what people will see if they buy the camera too.

I remember having a bunch of discussion around this when HDR was starting to come out for stills. IIRC, Photoshop CS5 started adding HDR support around 2010. I think this was pre-HDR displays so things were simpler then. Back then we used to just convert all HDR to SDR since there were no HDR displays. Now it’s more complex, haha.

We never used to have to worry about displaying on both SDR and HDR displays. It was just color calibration but even then it was just for times when others were also using calibrated displays for publication in print or on the web. For sharing snaps with friends and family, calibration was mostly irrelevant.