Review: DJI Inspire 2 with Zenmuse X5S Camera

I have been flying model planes for some years purely as a hobby, starting with slope-soaring gliders. I live near Brighton, England, which boasts many beautiful scenic locations for that particular combination of lift and accessibility—offering conditions perfect for surfing, where the landscape and the wind direction come together at specific moments to create the opportunity for a perfect fly.

As I discovered video technology was miniaturizing to a size that a model could carry it, I started to experiment. The opportunity to create a live transmission link from a miniature camera flown at 1,000 feet is irresistible; for comparison, when I first started delivering point to point and contribution feeds more than a decade ago, I used to take out a Mercedes Vito packed with all the technology required (Figure 1).

Figure 1. All the tech required to live stream on-location—as of more than 10 years ago.

Today, it is possible to deliver higher-quality video live-to-air from the air via only a smartphone, admittedly with a few limitations.

Just for measure, I typically use a tiny (1.5 square centimeter) camera that will transmit up to half a kilometer to a pocket-sized receiver (Figure 2). While it generates SD PAL video at 640x480, it does highlight how fast technology is improving. Digital HD 1080p camera systems are already common on many racing drones, and they are only marginally larger, although still an order of magnitude more expensive than this one. This price point is dropping fast though.

Figure 2. The tiny (1.5 square centimeter) SD camera is fine for hobby video, but can't hold a candle to the HD and 4K cameras used by the pros.

My interest in the aerial video space has also led me to organize a number of the early large drone races in the UK, and I founded Hidden-Valley flying park near me.

The result is a happy accident that finds me in the center of the emerging drone community, while being able to essentially treat it as a hobby.

In January, DJI asked if I would like to test fly their top-of-the-line DJI Inspire 2 and put its streaming capabilities through the paces.

Most of the reviews of expensive drone systems focus on the high-end sophistication, the bells and whistles, and the unique selling points. This is natural: From a buyer's point of view, particularly one who wants quality and future proofing, these aspects are critical.

But there is still an important focus on specific applications, and while I could wax lyrical about all sorts of video production-centric features (and I will touch on some of them), you're reading this because of your interest in drones and streaming. So I am going to focus on this function, and put other comments within that context.

Expectations

For reference I do not usually fly as a videographer. My own flying is primarily freestyle, and I fly what most would call a racing quad copter. I fly with goggles, and use the tiny 5.8 Ghz analog cameras as shown above. I see what the drone sees in the goggles and enjoy zipping about, from up high to low through trees or derelict buildings. I piggyback a small $65 RunCam that records reasonable video at 1080p.

However, I do like to occasionally provide my colleagues at my company id3as with some nice 4K test video for our virtual workflow engineering, and for this I have a DJI Phantom 4. It has a good lens and sensor and great stabilization, and it's perfect for what I do.

So I'm quite familiar with the DJI GO app which is at the heart of out-of-the-box operations when flying DJI products. Other apps can be used for different projects. I mention this because the eventual workflow that is right for your project may not be possible with the DJI GO app. For example, some apps are more tuned to mapping or photogrammetry or 3D modeling. But all DJI users will use the DJI GO app—not least because it helps with managing the firmware on the device cleanly.

Within the app, during flying, you can see a live video feed from the drone. I use an iPhone, and you'll need at least an iPhone 5S to use the app. The phone connects via USB to the transmitter (the DJI-supplied controller), and all the extra features that the app offers are relayed to the drone through the transmitter. The controller also receives the video return from the drone, and delivers it to the phone via the USB link.

The DJI GO app recently introduced live streaming. In simple terms, the app instantiates all the key ingredients of a streaming workflow:

• Acquires the source live video
• Encodes it to a suitable streaming compression
• Packetizes it for delivery to a remote server
• Creates a contribution link and handshakes the server
• Delivers the video.

So ignoring all the excitement of the high-end Zenmuse X5S camera on the Inspire, and the awesome airframe that retracts its legs on take off (allowing unobstructed 360° movement of the camera), the Inspire is essentially a high end USB webcam.

I mention this because it is important to realize that the links (both radio and USB) are limiting factors if you are chasing pure quality. The video is compressed twice before it is streamed. This is a limitation for all radio/IP-based video links, but it's not a limitation specific to the Inspire.

The DJI Inspire 2 is capable of locally recording—to its SSD—an absolutely incredible cinematic quality image, comparable to an ARRI Alexa in some tests. I have, to be honest, never myself used a camera of this quality. I asked a friend of mine—Michael O'Rourke, who is deeply into camera technology and took the photos of the Inspire in this article—to provide a mini-review of the camera, which is at the end of this article.

Live streaming from the Inspire 2 is simple—all you need to be able to do is find the live streaming option in the menu, pop in your specific security and configuration details, and press go.

For this article I decided that the easiest way to share a sample video was to stream live to my YouTube account, and let you see the on-demand video. While I could also have tested the Facebook Live or Sina Weibo (the popular video-sharing site from China, where DJI is based), or even my own RTMP server, those would make it more difficult to share the video here.

But before we get to that video link, let me take you through the steps I took to create it.

Setup

As with all new technology, I immediately put the instruction manual to one side and started to try to get the system setup. The Inspire 2 arrived in its own ultralight but very strong case. The case is superbly deigned to make the large device compact and portable, but if I have any gripes about this system, it is like a jigsaw to put it back in this tightly fitting box. While for a film shoot this may be an irrelevant detail, if the unit was to be used for search and rescue or security operations, then putting the system away in poor conditions in a hurry is a little frustrating. I am very used to getting my racer out of its bag ready to fly, adding a battery, and taking off, all within moments.

The Inspire takes a good few minutes to unpack and setup, and slightly longer to put away—I found myself trying to work out how to get everything back in the box quickly as rain started. This might be something that DJI want to provide some options for, but a combination of planning and practice should speed that process up.

That said, the whole process took around 5 minutes, which is going to be absolutely fine for most use cases.

Straight Into the Air

Once the system was ready to fly, I hit the takeoff feature and the system automatically lifted itself up to a head height hover. It is a large system, and take off does have a "wow factor," both visually and in terms of noise, particularly those retracting legs (Figure 3).

Figure 3. Taking off, the Inspire 2 makes quite in impression.

YouTube Setup

Within the app I then navigated to the Live Streaming Feature (Figure 4). Getting live on YouTube took around 60 seconds after I pressed Go. Admittedly I only had 2 bars of 4G mobile signal, but I also think this type of startup latency is relatively normal with the YouTube Live platform.

Figure 4. Starting a live stream with the DJI GO app is simple.

One thing: I did plan to message some folks to watch live, but I felt uncomfortable to switch away from the DJI GO app to another app to send the link principally because I was already hovering. While the transmitter, and not the smartphone, actually flies the Inspire, my instinct was to remain as in control of the aircraft at all times, and switching to a messaging app felt like I was reducing that control.

Controls

After flying the Phantom 4 a lot, the Inspire felt like a different machine. At first, being used to a forward-facing camera, I was thrown by the 360° camera—the default setting did not lock it in that familiar forward position, so my sense of which way the machine was pointing, and how that correlated to my control stick movements, was at first unclear. However, the problem was resolved quickly with a press of an option on the app screen.

I immediately noticed it was fast. I didn't have to actually fly fast; I could tell from the sensitivity and range on the sticks that movements take much less pitch than the Phantom 4.

As are all the recent DJI products, the Inspire is armed with numerous proximity sensors. These are set to 10-meter range, and having become used to flying my racer just a few feet from obstacles, I was thrown by the alarms and loss of movement as I tried to fly over some derelict buildings near the takeoff point. These ranges can all be adjusted, but once I worked out the limitation I focused on the flight and filming.

The details of that are probably beyond the scope of Streaming Media content, although obviously very happy to chat via email if there is more you want to know (click on my byline for my email address). The Inspire 2 flies beautifully, and the all-important gimbal is probably more stable than most tripods, despite having a huge amount of vibration and movement to deal with.

But lets focus on the streaming.

One simple detail that is worth mentioning: you should set your smartphone to "do not disturb."  While I did actually do this, in the middle of the flight my phone rang from someone in my exceptions list, and the incoming call connection appeared to have cut off the YouTube stream. There was no alert about this, so I carried on flying for a few minutes without noticing the red On Air indicator had gone out in the app window.

This is an interesting issue: You need to leave the phone on to stream, but incoming calls seemed to at least pause the streaming, if not actually stop and finish the stream. I did not notice before I had landed and deactivated the aircraft, so in my limited test I cannot be certain. The only way around this problem I realize is to not have any exceptions to your "do not disturb" iPhone contact list setting (or Android equivalent). Beware of this issue. It could ruin a key stream.

Post-Flight

As soon as we got back, we opened the YouTube archive.

The first thing we noticed was that the quality was spectacular for a smartphone-generated livestream, particularly given the marginal phone signal I had.

The second thing we noticed was that we had no idea the audio in the stream was being taken from a microphone on the transmitter. At one point I was talking to those with me briefly about an unrelated third party. I did not want this to go out on the archive linked to this article, so I had to replicate the video with a free ambient audio track from YouTube's online video editor. I believe all it the YouTube editor process did was remux the master video with the new audio (rather than create a new encode of the video) and then various other bitrates are pulled through the encoding process, as they are initially required in the CDN. So the video quality looks identical to the master to me, even though the audio has been substituted.

The archived version of our test video. 

Overall, given conditions, and the marginal signal, the quality is impressive. Sadly, we didn't have a clear sunny day—bless the UK—for the duration of the loan. I would have liked to repeat the test with sunlight.

So what do we notice in the archive?

Well the first thing that stands out are the video jumps. I had a look for advice on YouTube but I didn't immediately find a clear answer. My guess is that dropped frames (caused by perhaps low 4G bandwidth or signal variance from rain fade) are set by YouTube's workflow to be discarded rather than being written to archive. This probably, as a whole, stops YouTube archiving broken or black sources endlessly (which would give them a long-term storage nightmare).

The result is that in places where the stream was transmitted less than the tolerance level allowed, and where the audio stream was lost too, the archive appears to jump forward to a point where the signal was within tolerance.

Ultimately, this wasn't a problem; in some ways it saves some editing time. To restore a full archive, with the correct length of video (perhaps to match other video content in an editor), it would make sense to use the onboard video, compress that, and upload it to YouTube. In many applications that would be standard practice, since the SSD will contain the full content and can potentially be delivered to YouTube in far higher quality than the live stream was. But obviously that would add time to the turnaround.