Monitoring 3G

Both broadcasters and film producers are starting to think about moving over to 3Gb/s video. Roger Fawcett looks at the issues in monitoring 3G including new data formatting requirements and A and B data packing modes.
Analysis, Delivery & Transmission
Analysis, Delivery & Transmission
Analysis, Delivery & Transmission

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Both broadcasters and film producers are starting to think about moving over to 3Gb/s video. Roger Fawcett looks at the issues in monitoring 3G including new data formatting requirements and A and B data packing modes.

From a technology perspective, 3G infrastructure is not significantly more expensive than HD, so many facilities have already opted to future proof their installations by installing 3G-ready equipment and routing - both of which have been readily available.

What hasn't been available until very recently has been test and measurement equipment with which to monitor 3G video. 3G technology is attractive to both broadcasters and film producers through having the potential to answer some long-term problems.

A major problem for broadcasters has been the way there have been two standards in place for HD transmission - 1080i and 720p. Having dual standards inevitably means that programmes have to be delivered in both formats or converted from one standard to the other.

However, neither 1080i to 720p conversion or 720p to 1080i conversion is lossless. De-interlacing any interlaced video results in unwanted artefacts, while video produced by upscaling from 720p to 1080i inevitably lacks the high frequency content of a 1080i original.



Using the 3G 1080p standard as the production format for HD, however, could provide a neat solution to these problems through being able to because it can be converted losslessly to either 1080i or 720p. 3G also offers the capacity to transmit two unrelated videos down the same wire.

For film producers, the problem has been achieving sufficient colour depth in the 2k 24sf format used for film digital intermediates. Despite the frame rate being relatively low, film producers working in the current 1.5G HD formats need to use dual-link input in order to achieve 12-bit colour depth in either a RGB or XYZ 4:4:4 format. If they were to switch to 3G technology, just one cable would be needed to carry this data.

Another possible route for film producers is 10G, which offers even better resolution than 3G through its support of 4k formats and Sony, for instance, has recently produced a 4k projector, the SXRD 4K.

The disadvantage of 10G, however, is that it uses fibre whereas a distinct advantage of 3G is that it can be transmitted on the same 75 ohm coax cables as SD and HD, and moreover works at similar cable lengths.

Being able to use the same infrastructure makes 3G very attractive because it means it is both backwards compatible with SD and HD, and relatively cheap to implement.

In fact, it is even more cost effective thanks to recent Xilinx FPGAs and Gennum cable drivers and cable equalizers that support 3G alongside HD and SD, which are no more expensive than earlier devices and make it relatively painless for broadcast production facilities of all types to upgrade to handle 3G alongside SD and HD.

There is also support from our Advanced Video Development Platform, which provides a reference design for developing 3G products and includes format conversion IP.

1080p also has a further advantage over 1080i as a broadcast transmission standard in that it provides more efficient compression than interlaced formats and wouldn't need to be de-interlaced for display on today's LCD and plasma screens.

However this is not something that is going to happen in the short term as it would involve rather more significant changes to the infrastructure, starting with new set-top boxes for everyone.



The problem of monitoring 3G

Monitoring 3G is not an easy task for producers of test and measurement equipment. For one thing, the introduction of 3G transmission has led to an explosion in the range of video standards that can be transmitted.

This means in the region of 500 different video standards need to be correctly identified and monitored. (It isn't currently obligatory to include SMPTE 352 ANC packets in SD and HD video so we can't rely on that information being available to tell us what the video standard is).

Having 500 video standards to deal with has also made the process of picking the required output video standard rather more complex.

However, this is just the start of the issue because 3G transmission standards come in different types.

The simplest type (known as Level A) simply doubles the frequency applied to an equivalent HD video standard, making for example 1080p30 into 1080p60.

3G Level B standards, however, interleave on single channel the video streams that would previously have been delivered on the separate channels of a dual-link transmission.

On top of this, there is a 'dual-stream' option allows a single 3G channel to carry two unrelated video streams.

Another thing to be borne in mind is that 3G is a new standard and is still developing. The audio aspects of the standard haven't been defined yet.

This means that it is important to install test equipment that can be adapted to cater for changes in specification as they arise.

In practice, this means choosing test equipment that is field-upgradeable with the latest version and probably supplied by one of the more major companies in the field (because these are most likely to keep abreast of changes as they happen).



The good news is that the various difficulties in monitoring 3G video are being overcome. Indeed, this year's IBC sees the launch of more than one 3G-capable waveform monitor.

Roger Fawcett is managing director of OmniTek.

 

OmniTek set to launch OTM 1000 waveform monitor at IBC 2008

The OmniTek OTM 1000 is a fully-scaleable waveform monitor, which in its base form supports SD video but is easily upgraded to also support HD, Dual-link and/or 3G video with little change in the interface.

The OTM conforms to all the accepted protocols and, to make it as easy to use as possible, the selection of buttons on the control panel have been deliberately chosen to be similar to the ones used on other systems and so feel very familiar.

The compact display is high resolution and displays waveforms as well as a range of other analyses such as colour gamut, system timing, video and audio status, and audio PPMs. The OTM also offers on-screen help and, uniquely among other such system, can include a video generator which will certainly be useful in the early days when little 3G video is available for use as test material.

In case required, the OTM also offers such things as an audio jack and a USB connector on the front panel, also the option of control via a mouse and keyboard using very much the same display as the standard button-driven version.

Should additional display clarity be required, the OTM includes a VGA output supporting up to 1920 x 1200. However, users need to be careful in their choice of VGA monitors because they need one that not only supports 3G transmission standards but one that is also capable of displaying video at a quality that properly reflects the resolution and the colour depth of the transmitted signal.

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