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So, the line in my script reads…

writeb 0xC06CC426 0x21

You’d just switch out “0x21” for whichever video mode you want to use as your default.

Increase max filesize

Along with higher bitrates comes larger files. The Yi Action Camera has a filesize limit of about 2GB. It’s a number that crops up often, due to FAT32 file system limitations. But, who uses FAT32 any more? This limit can be bumped up to 4GB (I don’t think it can be removed entirely), resulting in fewer files. For firmware 1.2.13, again, it’s a single line.

writew 0xC03A8520 0x2004

Adjusting the image

This is where things get a little complicated, because we start to see see lines of code with numbers that seem to make no sense at all. The short version is for me to tell you to just go and grab YiMAX-PRO, the script which the “hacked” camera was running in the video above.

You can see in the images below the difference it makes once you correct the contrast in something like Premiere Pro or DaVinci Resolve. These are

100% crops.

The difference on this shot with lots of backlighting, moving water, and leaves blowing is even more drastic.

Aside from the amount of compression in a 10mbps file, the footage comes out of the Yi with what users describe as a “watercolour” effect. There’s some pretty major issues with the picture itself which YiMAX-PRO helps to overcome.

YiMAX-PRO reduces the contrast, colour, sets the exposure to retain highlight detail, and disables in-camera sharpening & noise reduction. This results in a pretty flat image, by default. In the below example, the stock camera is the more contrasty vibrant image. The other image is the flatter, desaturated “straight out of camera” image produced by YiMAX-PRO. This isn’t a crop, this is the entire frame scaled to fit the website.

It’s certainly not Log footage. It’s not even Cinestyle. But, it is a much better starting point than the default footage that comes out of the camera. Yes it needs a little work in post to give it some life, but that’s the entire point.

Also, if you want to keep the colour and contrast, but just disable in-camera noise reduction & sharpening, you can do that, too. That’s the beauty of scripts with codes that only span a line or two each. You can enable and disable overrides at will.

But let’s look at some of the options.

Vibrance/Saturation

This is one of those lines I was talking about with numbers that don’t seem to make any sense. But there are two spots that do.

t ia2 -adj ev 10 0 [vibrance] 0 0 [saturation] 0

The numbers used in the YiMAX-PRO script, and sets vibrance at 140, and saturation at 150. But, you can play around with these according to your own personal preference.

t ia2 -adj ev 10 0 140 0 0 150 0

Shadow/Highlight Clipping & Gamma

This one kinda makes half-sense. The number in the shadow one I don’t understand. It takes a value between 0-255, and the higher the number the brighter the shadows. The number you want to change the one at the end, which is “163” in this example.

t ia2 -adj l_expo 163

Highlight detail is a little easier to understand. Again, it’s a 0-255 number. Here, the lower the number, the sooner highlights blow out to pure white. In this example, the white level is set all the way up to 255 to retain as much highlight detail as possible.

t ia2 -adj autoknee 255

Gamma is set similarly. Again, the number is 0-255.

t ia2 -adj gamma 200

Noise reduction & sharpening

This is one I can’t really explain much about. This is something that Nutsey (the author of YiMAX-PRO and several other Yi scripts) figured out all by himself. Exactly how the numbers work or the consequences of changing them isn’t documented. Yes, I could just try changing them myself and see what happens, but given that the script just works for me right out of the box, I haven’t tried that yet.

It should be possible, however, to remove everything from the YiMAX-PRO script except the bitrate, noise reduction & sharpening settings. This would give you similar contrast and colour to the original camera footage but without the high compression or software artifacts.

Other Stuff

The list of things that can be changed is quite long, but finding out the information to get things exactly how you want will require a little legwork. The folks over on the Dashcam Talk forums have put an amazing amount of work into testing this camera’s limits.

For more information on the “t commands” to change how your image looks, check out this thread on Dashcam Talk. Other things you can make your camera do on the GitHub repository include RAW Photo mode, and an FTP Server to download files over WiFi from your camera.

Ready made scripts

There’s still a whole lot of this that I’m trying to learn and figure out myself. So, scripts make life much easier. Two of the best are XYC and YiMAX-PRO.

XYC, or “Xiaomi Yi Configurator” is a huge script which allows you to telnet into your camera. From there, you are confronted with a menu which allows you to configure things on the fly. It lets you change all the settings the default app won’t allow you to. There’s a hell of a lot of work gone into this one, and it’s probably the most interactive and user friendly script out there for the Yi.

YiMAX-PRO is the script I use. It’s the one I suggest everybody uses when they know they’re going to want to keep the same configuration time after time. I basically have two setups that I use on my Yi cameras (I have 6 of them now). Either I’m shooting 1080p24, or I’m shooting 1080p60. So, I have two copies of YiMAX-PRO on my desktop, each in their own folder. One is modified for 1080p24, the other for 1080p60.

When I know in advance that I need 60fps, I’ll load up all my microSD cards with that script before I head out the door. Otherwise, the 24fps script is transferred to the cards by default after they’re formatted.

So, if you want to be able to randomly change things on the fly and see what stuff does, get XYC. If you know what settings you need and want a good quick starting point, get YiMAX-PRO and customise it to your needs.

What about the new Yi 4K?

The bad news is that there’s very little information out there on hacking the new Yi 4K action camera. The good news is, we may not need it. Yi are getting ready to release the Yi Open API, which would allow us to legitimately override the camera’s settings.

The Yi Open API is aimed at software and hardware developers, which is very cool and interesting news. One of the reasons I have six of the original Yi cameras is for a 360° rig. Not being able to synchronise all the cameras and trigger them at once, is a pain.

Regardless, the Yi HD still costs a little over a third of the price of the new Yi 4K, and if 1080p is all you need, then why not? Of course, the Yi 4K also comes with a built in LCD and double the battery life. So, there are compelling reasons for both cameras.

Where can I find out more?

There’s information darted around the web, but there are several main places I’d recommend for further reading.

Of course, you can also find out more about the camera itself on the Yi Technology website.

Is that it?

Yeah, I think so. It was difficult to know how much to include in this post, and where to suggest reading more elsewhere. The post could’ve easily been three or four times as long, with a whole bunch of meaningless settings that most people wouldn’t have found that useful. So, I tried to include the most important ones and reference the rest.

I’d originally planned to just get one of the Yi action cameras for the Photokina trip so I wasn’t tying up my phone the whole week. Then, eventually replace it with a GoPro when a good deal came along. After playing with the Yi for a couple of weeks, though, it was an easy decision to not only stick with it, but to get more.

Having several makes shooting behind the scenes footage during shoots a doddle. Instead of having to keep taking breaks to move the camera to other angles, I can just setup a few of them, leave them recording, and cut between them in the edit. Having six is also kind of essential for the 360° rig. Speaking of which, you can download the plans to 3D print your own on thingiverse.

I’m not in any rush to go up to 4K, but the Yi 4K is looking very tempting from what I’ve seen so far.

Do you use either the Yi HD or new Yi 4K action cameras? What do you think of them? Have you come up with any unique hacks for them? Are you facing any challenges with them? Let us know in the comments.

About John Aldred

John Aldred is based in Scotland and photographs people in the wild and animals in the studio. You can find out more about John on his website and follow his adventures on YouTube.