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Lenovo Mirage VR180 Camera API client - remote control and custom live streaming

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# egarim
Lenovo Mirage VR180 Camera API client - remote control and custom live streaming

## Introduction

The Lenovo Mirage Camera with Daydream is a twin-sensor VR180 camera which does 3D photos, videos and livestreaming at 4k. It uses the VR180 format popularised by Google for use with VR headsets. Unfortunately, the format and the camera seem to have been abandoned, but it's still available for about $100 and is great value for what it does. The camera lacks a viewfinder or preview screen and needs a smartphone companion app (Google's VR180 app available on Android and iOS) to function as a viewfinder, setup the parameters for livestreaming, etc. Only Youtube livestreaming is enabled by the VR180 app.

The reference implementation of the camera firmware has been open-sourced by Google (https://github.com/google/vr180), but the companion app is not . This project provides a Linux/Python utilities which can function as a "companion app" to pair with the camera, issue API commands, setup live streaming with custom end-points.

## Installation

Instructions below apply to Ubuntu 18.04, YMMV for other distributions.

First, packages to be installed:
```
sudo apt-get install default-jdk libdbus-1-dev python3-dev libglib2.0-dev libcairo2-dev libgirepository1.0-dev
```

Run `make` to compile the Java files. These are taken from the Google VR180 camera reference implementation, so we get to use the exact same crypto code the camera is using. We can write python equivalents, but why bother? Life is short.

Then setup the python environment.
```
virtualenv -p python3 /path/to/egarim-ve
. /path/to/egarim-ve/bin/activate
pip install dbus-python protobuf PyGObject
```

## Basic Usage

The camera uses an application level pairing protocol over Bluetooth which uses ECDH key agreement to establish a shared key. This key is then used to encrypt further API calls over Bluetooth, and/or to sign HTTP API calls over Wi-Fi.

Before using the camera we must pair it using `bluestrap.py` (works only on Linux). Once paired, the shared key may be used with `egarim.py` to issue API requests over Wi-Fi on any machine (Linux/MacOS)

The LED surrounding the shutter button is in one of 4 states:
  1. Off - the camera is sleeping/powere off.
  2. Blinking green - the camera is booting.
  3. Solid blue - the camera is booted/awake and ready for action.
  4. Blinking green/blue - the camera is in pairing mode.
  
### Pairing

This 'pairing' is not the same as Bluetooth pairing with a number code - don't bother going to your OS Bluetooth menu and looking for the camera to pair.

Power on the camera. Once the shutter LED is in the solid blue state, hold the shutter button down for 5 seconds, until the LED enters the blinking blue/green state. Run

`python bluestrap.py pair`

If successful, you will see a series of messages like

```
waiting for device (attempt 1 of 30)
waiting for device (attempt 2 of 30)
found camera
waiting for service endpoint (attempt 1 of 30)
key init request type: KEY_EXCHANGE_INITIATE
key_exchange_request {
  public_key: "\003\033..."
  salt: "\360\316.."
}

key response response_status {
  status_code: OK
}
request_id: 0
key_exchange_response {
  public_key: "\004\063..."
  salt: "\160\216.."
}

Pairing response received; press shutter key once within 5 seconds to confirm
key finalize request type: KEY_EXCHANGE_FINALIZE
key_exchange_request {
  public_key: "\003\033..."
  salt: "\360\316.."
}

key finalize response response_status {
  status_code: OK
}
request_id: 0

Pairing finalized! Shared encryption key written to  me_cam.skey
cleaning up..

```

Press the shutter once when asked, and the pairing will continue and generate the shared key file, `me_cam.skey`. This file will be needed for all further communication with the camera. Run `python bluestrap.py status` to check that the pairing and credentials are valid.

### Bluetooth API calls

Once pairing is done and we have the shared key, we can issue commands over Bluetooth or HTTP. Bluetooth is useful to pair, set the wifi creds, and check status to get the camera's IP address.

```
./bluestrap.py config_wifi --ssid <SSID> --password <password>
```

The camera's Wi-Fi LED lights up when connected. Use `status` to find its IP address. This command also caches the results to `~/.egarim-status`, so the IP address can be found for HTTP API calls.

```
./bluestrap.py status

...
http_server_status {
    camera_hostname: "192.168.1.44"
    camera_port: 8443
    camera_certificate_signature: "0A\002.."
  }
...
```

To factory reset the camera,

```
./bluestrap.py factory_reset
```

### HTTP API calls

To issue HTTP calls, we need the shared key as established by a previous bluetooth pairing process (by default, stored as `me_cam.skey`) and the IP address of the camera (found using `python bluestrap.py status`).

To get the camera status using HTTP,

```
./egarim.py --host 192.168.1.44 status
```
In normal usage, `--host` is not required as the IP address is retrieved from the value from the last cached status received over Bluetooth. Run `bluestrap.py status` whenever you change Wi-Fi APs to refresh the status cache.

### Taking a photo

To take a photo, we first need to set the capture mode to `photo`, (optionally) configure the resolution, and then initiate a capture.

```
./egarim.py config_capture -h
```

shows the list of available capture configuration options to be set. For photos, only `width` and `height` are relevant. At a minimum, we set the capture mode:

```
./egarim.py config_capture --mode photo
./egarim.py status | grep active_capture_type
```

The last command should print `active_capture_type: PHOTO`. To click,

```
./egarim.py start_capture
```

You should hear a shutter noise as a photo is captured. Taking a video is similar, except there is an additional `egarim.py stop_capture` to terminate the video.

### Custom Live Streaming

The VR180 companion app only lets you live stream to Youtube. To stream to a custom end-point, e.g. one running at `rtmp://192.168.1.43/egarim_sample` with the stream id `foo`,

```
./egarim.py config_capture --mode live --rtmp_endpoint rtmp://192.168.1.43/egarim_sample --stream_name_key foo
# verify with status
# start capture
./egarim.py start_capture
# stop capture using the shutter button or the command below
./egarim.py stop_capture

```

If the camera goes to sleep, the live streaming parameters are lost, so always set them with `config_capture` before `start_capture`. Wifi connections in the 5GHz band are preferred for live streaming at high resolution. Many routers have different SSIDs for 2.4 and 5GHz - given a choice, pick the latter.

### Setting up a Custom Live Stream Server

There are many RTMP server solutions; here is a minimal setup using Ubuntu 18.04 and nginx.

```
sudo apt-get install nginx libnginx-mod-rtmp ffmpeg
```

Edit `/etc/nginx/nginx.conf` and append the following lines to the bottom:

```
rtmp {
    server {
        listen 1935;
        application egarim_sample {
            live on;
            record off;
        }
    }
}
```

and reload nginx using `systemctl reload nginx`. Firewall issues are beyond the scope of this README.

Start live streaming from the camera using the steps described in the previous section, replacing the IP address in the example with the IP address of the server on which nginx is running. To view the live stream from the same machine,

```
ffplay -fflags nobuffer rtmp://localhost/egarim_sample/foo
```

The `nobuffer` flag reduces latency to about 500ms.

### Media Management

To list, download and delete images and videos from internal storage, use the `list_media`, `get_media` and `delete_media` commands. Examples below:

List files in camera internal storage
```
./egarim.py list_media
# each line contains pathname, file size, video duration in ms, width and height
/storage/emulated/0/DCIM/VR180/20200218-051539536.vr.mp4 1238976 5868 2560 1440
/storage/emulated/0/DCIM/VR180/20200218-051539556.vr.jpg 3243859 0 3016 3016
```

Download a file to /tmp
```
./egarim.py get_media --dest /tmp /storage/emulated/0/DCIM/VR180/20200218-051539536.vr.mp4
```

Delete a file in camera internal storage
```
./egarim.py delete_media /storage/emulated/0/DCIM/VR180/20200218-051539536.vr.mp4
```

Download all files to /tmp
```
for i in `./egarim.py list_media | awk '{print $1}'`; do
  ./egarim.py get_media --dest /tmp $i
done
```

Delete all files in camera internal storage
```
for i in `./egarim.py list_media | awk '{print $1}'`; do
  ./egarim.py delete_media $i
done
```

## Advanced Usage

Read `camera_api.proto` and implement new commands `¯\_(ツ)_/¯`

## Technical details

## Credits

1. Google's VR180 reference camera implementation: https://github.com/google/vr180
  2. Dash Zhou's ECDH key agreement project https://github.com/zhoupeng6d/openssl-key-exchange, which uses the same key generation mechanism, but very well-explained.
  3. Adafruit's BLE project for Bluetooth/Linux details: https://github.com/adafruit/Adafruit_Python_BluefruitLE

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