Cameras appear zoomed in randomly
<!-- You must use the issue template below -->

**Describe The Problem:**
<!-- A clear and concise description of what the bug is. -->
My camera outputs 2560x1920. Sometimes when viewing the cameras, they are "cut off". They appear zoomed in. The problem seems to happen on snapshot and video. 

**To Reproduce:**
<!-- Steps to reproduce the behavior. -->

Setup a 2560x1920 camera using my settings below, and view them several times. 

**Logs:**
<!-- Bug reports that do not contain logs may be closed without warning. -->

```
N/A
```

**Homebridge Config:**

I know a videoFilter should do nothing here, but without it the cameras always appear to be zoomed in rather than being intermittent.

```json
            "videoConfig": {
                "source": "-rtsp_transport tcp -i rtsp://<>:554/Sms=2.unicast",
                "stillImageSource": "-i http://<>cgi-bin/api.cgi?cmd=Snap&channel=0&rs=wuuPhkmUCeI9WG7C&user=&password=",
                "maxWidth": 1920,
                "maxHeight": 1080,
                "forceMax": true,
                "preserveRatio": true,
                "vcodec": "copy",
                "videoFilter": "scale=1920:1080",
                "audio": true
            }
```

**Screenshots:**
<!-- If applicable, add screenshots to help explain your problem. -->

Displaying wrong:
<img width="385" alt="Screen Shot 2021-06-30 at 6 48 48 PM" src="https://user-images.githubusercontent.com/3227962/124040903-d16f6f00-d9d3-11eb-80d1-4e9b60080935.png">

Displaying correctly:
<img width="383" alt="Screen Shot 2021-06-30 at 6 56 18 PM" src="https://user-images.githubusercontent.com/3227962/124041453-dc76cf00-d9d4-11eb-94b9-4b9dfd564686.png">



**Environment:**

* **Node.js Version**: v14.17.1<!-- node -v -->
* **NPM Version**: v6.14.13<!-- npm -v -->
* **Homebridge Version**: v1.3.4 <!-- homebridge -V -->
* **Homebridge Camera FFmpeg Version**:
* **Homebridge Config UI X Plugin Version**:
* **Operating System**: Docker <!-- Raspbian / Ubuntu / Debian / Windows / macOS / Docker -->


<!-- Click the "Preview" tab before you submit to ensure the formatting is correct. -->
