The Mobile Viewpoint CellMux Backpack Solution: A Hands-On Review
Every time I write an article about the link-aggregator and CellMux (video-specific link aggregator) space, a new vendor contacts me and berates me for not including its product, or for not reviewing the latest features it has. So I set about the whole process of asking the vendor to send me a rig to try out, pointing out that I can't know everything and that I do absolutely rely on vendors reaching out to me as much as I rely on Google Alerts to find me new vendor products as they appear.
Recently I approached Mobile Viewpoint of the Netherlands after a press release hit my desk announcing that it had been selected by the BBC for the mission-critical job of following the Olympic Torch relay as it completed its final stages on the way to London.
In response, Mobile Viewpoint managing director Michel Bais reached out with a compelling email, essentially offering to simply fly over to my office in Brighton and lend me a rig to test for a few days. Confidence in his kit really came over.
I have, on several occasions, sought CellMux rigs to play with for a few days on my own, to devise some form of scientific process by which to benchmark these technologies as I review them in these pages, and it has proven very difficult. Perhaps this has been my fault for suggesting I line up a "shootout"; as I have mentioned in previous articles, all the vendors have felt that a straight side-by-side shootout could prove damaging to the positioning of their technologies, because each is highly susceptible to spurious environmental considerations such as contention on the local cell mast and with other similar devices. Most of the vendors have been concerned that my tests could adversely and unfairly represent their kits.
To an extent I can see their point. But with my cynic's hat on, I also feel that if these companies are serious about offering this technology to newsgathering agencies (which they universally are), then they need to be pragmatic about the fact that in some circumstances their kits simply will not work.
Indeed, even the "highly reliable" satellite newsgathering systems are on occasion hit by rain-fade. It's just a fact -- when you reach out to the edge, in the field, there are many risks that can affect your ability to get a signal back to base.
Anyway, I was extremely impressed by Bais. His sales position and pragmatic viewpoint kept his expectations in line with reality and with what the technology really did. He wasn't worried about it not working at times -- of course that will be the case. He just took the view that if any of these CellMuxes could work, his would do the job well. There was little to add.
He simply flew over to England, sat in my house in Brighton with Hedley Baldwin (the U.K. reseller of Mobile Viewpoint), and ran through the rig with us. Then he left it with me for a few days -- something that none of the other vendors have yet done (and I invite them to do so in the future).
This gave me a brilliant opportunity to gather a few interested partners and to conduct a series of investigations and tests to scientifically review (at least to an extent) the rig and its capability.
The tests that we ran should broadly be possible with all these devices, so I can, in the style of Top Gear's "Star in a Reasonably Priced Car," now actually rationally benchmark these technologies. I will now up the pressure on vendors to let me run this test on each of their devices as they come out.
Before I get into the test, how we conducted it, and how the Mobile Viewpoint rig fared, let me just give you an overview of the Mobile Viewpoint technology.
How Mobile Viewpoint's Technology Works
Mobile Viewpoint began as Triple IT B.V., a company focussed on providing IP video technologies for security and road monitoring; when Bais joined from the GSM and mobile sector, he quickly pushed the idea of a video-based link aggregator (or as you will know what I call a CellMux) and created Mobile Viewpoint. Growing out of their relationship with Dutch police and highway management, they developed a series of technologies ranging from a small belt-pack device called 3G-MCup to the high-end, backpack-carried WMT.
So, just as IBIS DMNG, TVUPack, and LiveU did, Mobile Viewpoint developed a backpack-carried product. The devices accept SIM cards from data-enabled mobile operators. Once the various APN names have been set up, the modems hook up, and each available data carrier is added to the pool of available routes and links for the device to forward its UDP video data over.
Once each packet is routed, it makes its way through the separate cellular networks, through their peering to the internet and over to the ISP to which the receiver unit, the WMT Backend Server, is collected (Figure 1).
Figure 1.The Mobile Viewpoint workflow
The receiver (techies would call it a demultiplexer) then buffers the stream a little (to allow for different packets arriving over different routes to be sorted into the right order), and decodes it. The output is then presented as an HDMI signal as I tested it, although other options are available, such as local streaming in RTSP, which we also used extensively in the testing.
The first thing you notice about this rig is the backpack's size and its unique, slightly funky, and definitely not-discrete antenna. While the Teradek Bond, which is at the other end of the spectrum, uses the data services' own "dongle" modems and its built-in antenna, looks like a spider when all its dongles are plugged in, and could be strapped on the back of an Action Man, the Mobile Viewpoint rig has a grey bulb on the end of a telescopic 2m-long pole that forms its antenna. The pack, weighing in at around 8kg-10kg, would crush an Action Man; indeed even a 6'4" engineer looks reasonably laden with the Mobile Viewpoint system connected (Figure 2, Photo 2012 by Michael O’Rourke, www.lightwhispererphoto.com).
Certainly, if you are working on the front line of a battlefield, you are probably going to feel a bit like a target with 2m of cell-mast strapped to your back.
About That Antenna
And this unleashes a set of interesting initial questions: when Bond has miniaturised to a camera-top model, and LiveU, IBIS, and TVU are the size of a box of chocolates (or smaller), all with an internal or small antenna solution, why does Mobile Viewpoint take such a stand-alone approach?
The truth is that Mobile Viewpoint is tightly focussed on operation and cosmetics. It turns out it added the antenna initially because a number of clients had expressed concern about having so much cellular "radiation" so close to their backs or heads for any prolonged period of time. The idea of the telescoping antenna was initially to put this transmission 2m away from the operator's head. However, this extension had a number of secondary benefits that actually made this modification a market differentiator.
This is not the first time I have zeroed in on antenna strategy as being the hub of the issue in the CellMux game. I have historically strongly favoured LiveU's patented high-gain antenna system as crucial to its differentiation, justifying LiveU's market leading position. While it is unclear (to me at least) if TVU infringes on LiveU's patents, I know that Bond and IBIS don't infringe the LiveU patent since they use the operators' dongle-modems.
LiveU's high-gain antenna gives it reach over the heads of local devices to further cell masts. This means that even if the local cell tower is saturated by whatever event is being covered, LiveU can reach those farther masts and get signal when others can't. It must also be mentioned that a particularly challenging issue has been raised that suggests this type of high-gain operation is, in some territories at least, not only outside of the standard operation setup of mobile phone networks but may in fact be illegal because the high-gain process is nonstandard and certainly could effect other users' fair access to the networks. I will be investigating this claim in a future article, but it is founded on the fact that one public broadcaster I spoke to felt that it was risky enough that he couldn't use the LiveU system for fear of regulatory compliance issues.
Mobile Viewpoint offers an alternative: by telescoping the normal antenna above the heads of the local crowd, the single largest absorption of radio waves (the water molecules in the people at the event) is avoided, resulting in a significant optimisation of the data path.
Other vendors argued that the attenuation in the telescoped length counters any gain from the height, but given that the antenna is not actually primarily being raised to increase gain but to decrease radiation exposure to the operator, this secondary, experimentally proven (see later), optimisation is a real benefit.
So, as with each of the technologies I have reviewed, the video signal into the system is then presented at the receiver. Despite the underlying use of IP streaming technology, Mobile Viewpoint and all CellMuxes should be thought of as a video signal acquisition technology, enabling TV playout centres or security operations centres to receive a video signal from almost anywhere in the mobile phone networks' footprint.
How We Tested
Let's talk about the specifics of my test now, so you can get a feel for the use and performance of the rig.
First let me introduce to you my two testing partners: Tim Thompson of Link -- Tim is an old friend of mine who has for many years worked with contribution feeds for video webcasting. Historically he (and often I) worked with VSAT IP links, since they were the most affordable way to bring ad hoc IP to remote locations. CellMux technology potentially represents something very disruptive to the VSAT IP, and in wider terms to the satellite video services sector. Now, instead of a truck and a half-hour dish alignment and the tethering to the truck, operators can be online within 90 seconds. They can be completely mobile, and since they are on foot, there is no van to get through the traffic jams building up around the event. Tim has been keen to test these systems to become familiar with when they are appropriate to put in front of his clients.
I also seconded a friend -- professional photographer and all-around polymath Michael O'Rourke of The Light Whisperer -- as our cameraman for the day. He has a terrific eye for detail -- better than Tim or me (who typically just focus on IP and routing, rather than picture quality).
We first tested that the system was working. Then, leaving the receiver (which always runs a DVR service, capturing up to 24 hours) on and connected to my domestic (Virgin cable) broadband line, we headed out, first to the local electronics store to buy a component or two that I needed.
The idea was that we would take a long drive with the link running throughout. The aim was to record the live stream back at my home office on the receiver and then to review this for quality on our return.
I only had a Sony Handycam available. While the unit can handle 1080p source, I fed it an SD PAL Composite video source. The device has quarter-inch audio jacks (in my mind a little unusual), but I only had RCA phone audio on my Handycam cable, so we elected to leave audio out.
We pushed the telescopic antenna out of the rear window of my car. Tim was in the back operating the unit, with Michael holding the camera and responsible for things such as ensuring a few shots of time-keeping devices to allow us to sync our data later. I then drove us out of Brighton, through the suburban zone north of the city, out onto the dual carriageway, out to a major roundabout near a local town called Lewes, then back again to Brighton, returning around the outskirts to my home office. This is a journey that covers nearly every aspect of typical highway cellular coverage from dense population to relatively remote rural areas.
To ensure we had detailed logs of velocity, GPS location tracking, and altitude, I used an app I usually use for jogging (LogYourRun) to log our journey.
The key reason we wanted to set up this way was to (admittedly probably far less scientifically) replicate the testing that the BBC undertook when selecting the Mobile Viewpoint technology for the Olympic Relay coverage. The key performance indicator is not rocket science: we were looking for a measure of how continuous the link was.
Now I must get into some of the detail of the device options so that you can understand the assumptions and account for the inherent errors yourselves.
One of the options available to the user is to vary the latency. To a savvy streaming audience (as I know you all are), this essentially means increasing the buffering over the link. While increasing the buffer reduces the number of dropouts -- points in the transmission where the buffer is starved and the stream stops until the buffer is replenished -- this also means that the time from input at the transmitter to output at the receiver is increased.
Tim and I come from a live sports and financial news streaming background, and typically these two areas are quite sensitive to latency. There are many scenarios that are less-sensitive, but we wanted to see the system performing with the 2-second latency setting, which actually delivered pretty much as promised; I have seen encoding platforms that claim X seconds of latency only to actually deliver many-times-X in reality.
It is important to note that Mobile Viewpoint and the BBC have developed their own buffering algorithm (CPT), which then gives a staggering 2-minute link-latency. This has been specifically developed for the Olympic Torch relay. It's a great model. If the signal drops away while the link is active, the backpack continues to create the high-quality stream -- typically 2.5Mbps H.264/AAC, even if a lower rate is all that is available. When the signal picks up quality again, then any packets that have been rerequested in the previous 2 minutes are sent over and above the live 2.5Mbps feed. These issuing packets are sorted and inserted in the buffer on the receiver, and the output signal is "reconstituted" back to the full 2.5Mbps signal. This means a continuous 2.5Mbps signal can be delivered even if the link drops out completely for many tens of seconds. If you can put up with the 2-minute latency, this is a unique and interesting feature, and it clearly helped Mobile Viewpoint win the opportunity with the BBC.
While we were aware CPT could iron out any link loss on our own test, we opted for the 2-second latency setting so that our test actually measured the carrier capabilities a little more closely.
With that description I will now turn to the results.
You can see our route in Figure 3. In advance we knew, by virtue of being local, where we expected to see dropout, and indeed our best guesses proved to be accurate. Our guesses collectively anticipated a dropout at point 12/14 as seen on the map, and at a point halfway between 20 and 22. The trial also showed a dropout at 2.
Figure 3. The testing route
Watching the video of the route is an absolutely clear way to see how successful the link was in any practical sense -- I have posted it here, but bear in mind that this was the original video from the receiver re-encoded to FLV and then uploaded to my YouTube account, where it was almost certainly re-encoded and definitely remuxed. While I think it looks good, it is important to be clear that this is a generation or two away from the source recorded on the receiver's DVR. (If you look closely in the first few moments, you may see a crazy dog running down the centre of the highway too!)
So from a subjective point of view, we can look at the video and really get an idea about how effective this technology can be.
A Scientific Measure of Cellular Link Quality
But I wanted to go a little further than that. With some amazing technical journalism in the pages of Streaming Media magazine from the likes of Jan Ozer and Tim Siglin, I wanted to actually come up with a scientific, quantitative way to measure the link quality.
Since the bitrate of the video stream as it was recorded at the receiver drops when the cellular link faded, I decided to try a wire-level packet analysis. In my mind this analysis is as rigorous as any other method I could think of, and I will attempt to use this method for all and any CellMux tests in the future.
Essentially, once the recording was saved on the receiver's DVR, I could connect to the DVR feature using VLC or QuickTime and an RTSP:// URL. As the stream then played back to my machine, I used Wireshark to capture all the packets specifically between my laptop and the receiver's DVR source. With just that conversation captured -- in essence every video packet played back -- I could then use Wireshark's IO Stats grapher to plot the data payloads by time. This is about as accurate a measure of the bandwidth of video that you could get, literally measuring the size of each datagram and plotting it against time. It doesn't allow for variance in the Wi-Fi signal between my laptop and the receiver, but the range was about 4m and the normal signal quality of this link is far higher than 2.5 Mbps. So while I should set up a control next time, I seriously doubt my Wi-Fi QoS affected the results I captured.
Our results can be seen in Figure 4. The top two graphs are taken from LogYourRun. The first shows velocity with higher points on the Y axis representing slower velocity. So from a standing start, we left the city and averaged about 60mph. The small slowdown at 15 minutes is the Lewes roundabout.
Figure 4. Our testing results: the top graph shows velocity, with higher points on the Y axis representing slower velocity; the middle graph shows altitude in meters; and the bottom graph shows video quality as measured by Wireshark.
The middle graph is the altitude in metres. The roundabout (point 16 on the map) represents the lowest point on the journey. We found this useful for aligning the data on the charts, but also to see how the performance was affected by the altitude -- particularly in the last 10 minutes when, despite being high, we still saw significant drop in signal.
So the final graph shows the video quality as measured by Wireshark, and the line -- pretty accurately in my opinion -- shows the variance from the target 2.5Mbps. Note that at many points the signal would have dropped and the adaptive bitrate encoding model in use over the link would have downgraded the encoding profile to fit within the available link capacity, so long as there was actually a signal available. This would have increased artifacting/pixellation and so on, but the fundamental flow of video would have remained solid throughout.
I also collected a number of graphs from a service called Sensorly that crowdsources (via mobile apps) mobile network operator coverage graphs. It was good to see that the coverage that Sensorly anticipated was in line with what we saw on the UI of the device.
Around point 2 we were in the Brighton suburbs, and accordingly some of the quality of signal loss would have likely been down to interference from buildings and contention with other service users. Between there and point 12 the signal was good; as we passed the university with its population of 7,000 to 8,000 people, the cellular quality was good and very stable (perhaps the small regular bumps every 30 seconds or so are down to the handover from mast to mast). At point 12 dense trees, unfavourable geographics, and an extremely low population density led to a loss, followed by a dip at the roundabout at point 16. Interestingly, as you can see in the video, there was a large police incident support unit near the roundabout, and I noticed it was covered with cameras. I wondered if the dip at the roundabout could have been contending with some communicators on that police unit.
As we returned to Brighton, we again passed point 12 with signal loss. Tim and I got very excited at the time about how the signal loss at this point is loosely symmetrical around the roundabout point.
The one signal drop that confused us was the one at point 21. As we crested the hill over to Woodingdean, we suddenly had line of sight to a very close transmitter. However, it seemed that the Mobile Viewpoint lost the signal completely as we came very close and passed the tower. We discussed this in some depth. Michael, Tim, and I all felt that this was a problem with the handover between the cells. We think that as we left the A27 road and headed up the hill we gradually got farther away from the tower we were connected to, which would have caused all our modems to increase their power, only to suddenly crest the hill, and be presented with a much more powerful mast. The theory is that that mast would have then immediately demanded that our modems drop their power significantly so as not to drown out other signal in the area. This quenching could have caused problems for our QoS-sensitive data application and caused the underlying link failure we saw.
So there were no real surprises that the link had a few drops at all, but none of those drops were even a minute long, let alone 2 minutes, so if we had used the CPT setting on the system, we would have achieved a continuous 2.5Mbps video contribution feed -- more than enough to have covered the Olympic Torch continuously.
The Verdict on Mobile Viewpoint
While this is an isolated experiment at the moment, now we have a model. I look forward to benchmarking other rigs in this way.
There are several other bits of practical information that have been fed back by Tim and Michael that should be included in this article:
- Tim particularly liked the antenna. Despite its size he had, until he saw the mast, planned to shield his back with aluminium foil. While he is (often) a little left of field, Michel assures me that Tim is not alone in being concerned about CellMuxes' radiation and its proximity to the operator.
- The kit is rugged. It is far from the smallest of these devices, but there is no doubt that its build is operationally focussed. It is rugged and easy to control, and it has some nice features on the UI such as "press and hold" on all buttons and touchscreen to avoid accidental knocks.
- It can run on mains, using a Vpower camera battery adaptor, or (as we did) off an inverter in a car cigarette lighter socket.
- There were one or two minor issues: a few of the cable connectors seemed to have been added as an afterthought, or the layout of physical connector interfaces is simply considered for a specific use case -- battery, SDI, in backpack -- and so while the SDI and power sockets were on the front, we found the composite connector (which needed a BNC barrel adaptor) on the side of the unit. This meant that by the time we connected our camera, the cable was pressed tightly against the backpack. The Ethernet cable socket was on the other side, and this again would have made it awkward to connect anything via Ethernet while using the case.
- The antenna makes the pack top-heavy when extended, so careful adjustment of the straps is needed to ensure the antenna doesn't pull the whole unit back too hard, like a small child hanging off your rucksack.
- With the telescopic antenna 2m above your head, 1) you look like an uber-geek, 2) it would be a bad setup for filming lightning strikes while standing on a hill, and 3) you need to remember it's up there before you go under any low wires or entrances.
The final use comment came after we tried to run a DVD through the system to test a higher-quality source than my Handycam. It was about 9 p.m. by the time we set this up. We fired up the unit indoors on the table in my room and started the stream running.
Surprisingly, I could really feel the effect of the radio emitter. Frankly, it felt like my fillings were trying to turn around and immediately brought on a mild headache, something like the effect of high-tension overhead power lines. Within a few minutes of the test, both Tim and I were feeling really uncomfortable, slightly edgy; we decided to turn the system off. The overall experience was quite unsettling. During the day there were a lot of stimuli to distract us, but in this evening test it was quite clear to me that having half a dozen radio transmitters blasting at full signal right near my head unarguably had an effect on how I felt.
Tim made a very interesting observation: if you were using one of these for an event such as a press conference, most of the people there would feel uncomfortable simply because of the radio transmission -- and this is a very real negative side effect of these types of devices. Admittedly, this is extremely hard to objectively measure, but once you have experienced it you won't forget it.
Thankfully for Mobile Viewpoint, the telescopic antenna really mitigates that issue, but next time I review some of the more portable camera-top devices I may get a tin hat to ensure my brain doesn't end up glowing like an Olympic Torch!
All in all, this is a premium product. The full-blown HD system with receiver is around €27,000. It is not sold with a service -- you have to arrange that yourself. It's UDP-based, which helps with the operating costs. The price is comparable with the TVUPack, LiveU, and IBIS DNMG units, certainly putting all of these vendors' products in the premium band compared to Teradek's Bond at around €7,000. Rightly so, Mobile Viewpoint is set to capitalise on the BBC's selection, and for broadcasters who are going premium there are many great reasons to give the Mobile Viewpoint route serious consideration.
While owning these tools is still prohibitive for many folks in the streaming media sector, it is clear that hire business will emerge soon. While clients for this type of product will remain focussed on broadcast, security, and emergency service, I expect to see more and more streaming workflows turn to CellMuxes as a quick, flexible, and disruptive alternative to satellite over the next few years.
I'm keen to hear feedback on the evolving benchmarking process. I'm very keen to run other vendors' products through this process, so please reach out if you think we could add tests and if you have kit to test.
With thanks to Michel, Hedley, Michael, and Tim.
This article was originally published in the autumn, 2012, issue of Streaming Media Europan Edition under the title "Review: Mobile Viewpoint."
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