When we heard that Tandberg had put some concerted effort behind finally entering the mobile TV space, our first thought was ‘What has taken it so long?’
There are a total of around 80 global trials for one form of mobile TV or another and these stretch back to 2004, and each one of these is likely to lead to a service, each using enough encoders to drive up to 25 mobile TV channels plus regional variations. The bigger the country, the more regional variations and the larger the encoding requirement.
Envivio and Thomson Grass Valley have made aggressive incursions into this market and are well ahead in terms of customer trials, while both Tandberg and Harmonic, usually so ahead in terms of putting the latest technology into action, up until now appeared to be ignoring the market.
We talked to Simon Frost, Business Development Director at Tandberg this week to talk us through the product.
‘What we’ve put together is an ecosystem so that it is a broad offering for DVB-H mobile TV. We have taken an existing product line, the iPlex that we inherited when we acquired SkyStream Networks, it was one of our multi-service IP centric IPTV platforms, and we have adapted it to for mobile and renamed it mPlex.
‘To do that we have eliminated those parts of the H.264 standard which use up a lot of processing power on the client side, we do this by embracing the baseline profile of H.264, rather than the main profile. This means we also no longer use Cabac which is computationally complex and don’t issue B frames, which increases the requirement for buffer storage.’
Cabac stands for context based adaptive arithmetic coding and is a mathematical intensive way of relating context and likely movement estimation for particular pixels. Cabac can reduce the bitstream dramatically, but it requires lots of CPU cycles to unravel at the other end. ‘All of this is very standard for mobile TV encoders,’ said Frost.
But the overall system from Tandberg includes devices to receive a TV channel, usually satellite receivers, a timing stream to synchronize single frequency networks using GPS, and an IP encapsulator from partner UDcast (see separate story) which manages Forward Error Correction and calculations on the maximum subscriber transport bandwidth and prepares the DVB-H timeslice. Tandberg will also offer the devices to uplink this back up to satellite, and deliver it to local transmitters and has also contracted with UDcast to supply its iSplicer, which drops localized content and advertising into the video stream, while recalibrating all of the channel’s timing information.
Frost says that the encoding chassis for mPlex has the processing power to handle 8 mobile TV channels at once, and is powered by Texas Instruments DSPs.
Rival Harmonic just introduced an encoder for HD encoding that does away with DSPs, and instead uses a new specialized encoding chip from Ambarella. ‘It’s true that for HD the stream size is so large that older architectures aren’t quite so good, because they have to break the stream up into separately managed streams, and Tandberg is addressing that with a combination of FPGAs and DSPs, but really that’s just for HD processing, not mobile TV.’
Currently the system is also supporting the scrambling for the DVB-OSF ISMAcrypt DRM system, and if alternative scrambling is required, the OMA 18Crypt that Nokia has so far favored can be supported through the UDcast encapsulator hardware.
The system at present is targeted solely at DVB-H, which means that it will slot in nicely with the DVB-SH from Alcatel, because in data terms that’s identical.
Will Tandberg chase the MediaFLO market? ‘We have thought about MediaFLO and the emerging Chinese standard, but the FLO system is tightly integrated and at present Qualcomm seems to be delivering its own hardware for encoding. But we are set up at present just for DVB-H.’ Which is reasonable given the amount of implementation work for DVB-H there is likely to be in the next two years with around 60 potential projects up for grabs globally.
Frost says that the system uses variable bit rate encoding and that where required it can use variable GOP lengths (changing the gaps between I frames dynamically) and what he called scene cut detection, when the encoder recognizes where a scene has been changed and generates an I-frame immediately. But Frost says that it won’t be pushing these things immediately. ‘Customers don’t ask about specific features, they tend to tell us how many channels they want us to deliver over a specific bandwidth and rely on us to tune the system accordingly.’
But he confirmed that ‘Yes customers are asking for more and more channels and most deployments out there are trials, are not yet at the number of channels they will need to be.’
Tandberg says the system is already scheduled to go into a couple of not yet publicized trials and the company is already responding to RFPs for both further trials and deployments.
Given all of this, it seems something of a shame that Tandberg’s new owner Ericsson has been so set against datacasting services for mobile TV, and in favour of multicasting. It’s likely that Tandberg will also be asked to apply is know-how to the cellular multicasting market shortly, which should be no great hardship.
In the meantime Frost says that Nokia is still friends with Tandberg, despite it being on a slightly frosty footing with its future parent and deadly rival Ericsson.
And what happens if after all Nokia Siemens Networks decides that it doesn’t want tons of DVB-H business going to a subsidiary of Ericsson, and elects to make a bid for its own encoder maker, say Harmonic? With convergence rampant that’s almost inevitable I’d say.