Litchi Android Video Feed Zoom?

[Bravofox]

I cannot find the answer to my question anywhere.

I have a Phantom 4. With DJI Go 4 on an iPhone, in 1080p video mode it has a 2x "Pinch to zoom" Feature, that you all are probably aware of.

My main Phantom control device is a Nvidia Shield K1 tablet and it is common knowledge DJI Go on Android does not support this feature.

So, does anybody know if Litchi supports it on Android?

 

[Andy Middleton]

Zoom can be done with Litchi but using the programmable C1 and C2 buttons (zoom in / out) and not via pinch to zoom as with go on IOS. I am also using a K1 as my main tablet

 

[Bravofox]

Zoom can be done with Litchi but using the programmable C1 and C2 buttons (zoom in / out) and not via pinch to zoom as with go on IOS. I am also using a K1 as my main tablet

Cool.
That sounds even better, as the pinch to zoom is a bit awkward while flying.
I am also having other issues with DJI GO on my tablet which makes me want to test Litchi.
At least I can get a refund within 2 hours of purchase if it does not work out.
Thank you.

 

[dwallersv]

Zoom can be done with Litchi but using the programmable C1 and C2 buttons (zoom in / out) and not via pinch to zoom as with go on IOS. I am also using a K1 as my main tablet

Interesting... is this only a zoom of the FPV view, or does it actually zoom the image captured on the SD card on the AC?

 

[Bravofox]

Interesting... is this only a zoom of the FPV view, or does it actually zoom the image captured on the SD card on the AC?

Mmmm. Very valid question!
I can see when you zoom in on DJI Go in iOS, that the recorded video on the SD card also get zoomed.
Technically, it does not seem to be a digital zoom, but rather a cropped 1080p image of the 4K sensor. So, you do not overzoom the image but only cut off a large border to fit the video into 1080p.

If Litchi only zooms into the 720p feed on the FPV view, it will be very pixelated and not very useful...

 

[dwallersv]

Mmmm. Very valid question!
I can see when you zoom in on DJI Go in iOS, that the recorded video on the SD card also get zoomed.
Technically, it does not seem to be a digital zoom, but rather a cropped 1080p image of the 4K sensor. So, you do not overzoom the image but only cut off a large border to fit the video into 1080p.

If Litchi only zooms into the 720p feed on the FPV view, it will be very pixelated and not very useful...

Well, it's raining here in Santa Cruz, CA, but I can certainly power up the bird and give it a whirl sitting on the floor and see what happens... report back in the next hour when I get to it.

 

[dwallersv]

Well well well! That was a nice surprise, and also an interesting discovery I never noticed before.

First: Yes this does work for all 1080 framerates except for 120 fps. It zooms in in 0.1x increments, giving ten discrete zoom steps between 1x and the max, 2x.

Further, it is not just zooming the FPV in the remote display but is also recording the same on the SD card on the AC. Also it is clearly apparent that the local hardware/firmware is preserving resolution by cropping the full-resolution 4K sensor data to the zoomed frame and then scaling to 1080x1920 -- always decimating the image, thereby preserving maximum detail.

So, if you want a zoom function on Android, Litchi has it now. DJI must expose an interface for this in the SDK, Litchi's used it, but they haven't gotten around to porting the pinch-zoom implementation to Android yet.

In any case, this is a much better way to operate it. Zoom in on C1, out on C2. Much easier to focus on composition while zooming in and out.

Even better would be to hijack the right index-finger wheel for zooming. I'll contact Litchi and see if that can be done.

Second: Can't zoom in 1080, 120fps because the camera does a 2x zoom when you switch to 120fps!!! What's this? I never read that anywhere, in the manual, or in this bboard. Just checked it with GO and GO4 and it does it there too.

Why is it doing this? I have a guess: At 2x zoom the resolution is pixel-for-pixel 1080x1920. No decimation is necessary. This removes a significant bit of image processing, and therefore time for each frame. At 120fps, the system is just not fast enough to scale anything bigger than 1080x1920 to 1080 at that frame rate, so DJI just locks in a 2x zoom and records the pixel values directly.

 

[Bravofox]

Thanks for your feedback @dwallersv . Based on your observations, I purchased Litchi and tested it.
It works great! I was getting bad video feed glitches in GO and constant app crashes. Litchi manages the feed much better and did not crash once in my 20 minute test flight. (It seems that Litchi uses 32 channels instead of Go's 8. I know there is a hack for this, but I could not get it to work)
At first I was disappointed as the zoom did not work, but then I realized I was still in 4K. Put it in 1080p and presto!

I just wish there is a way to zoom 2x instantly and not having to press C1/C2 ten times to zoom in/out. I'll go through the app to check if there is maybe a setting for this.

So, this means I can keep my Shield K1 and not have to sell it and get an iPad mini...

Thanks again for your trouble!

 

[dwallersv]

I'm planning to contact the Litchi developer today to make an enhancement request to have the zoom configured like it is on one of the other aircraft (don't remember which one): hold C1 and turn the wheel on the right used to adjust camera settings.

I'll add to the message a request for a 2x/1x toggle feature that can be assigned to a button.