Viewpoint
Much has changed since the 50 and 60 Hz TV
My View:
standards arrived over 60 years ago. Today better
power supplies mean the ‘hum-bar’ problem is
gone, so TV no longer has to be locked to mains.
Apparently the NTSC crosstalk problem was
solved soon after the adjusted frequencies were
standardised - if only they’d waited! Surely a
single global standard, or at least a Standard
On the
Frame Rate, could have emerged when standard
definition television went digital. But no. Again
the opportunity was missed when the high
definition standards were launched. The ATSC’s
Table 3 introduced more TV frame rates; 24P I
right track?
guess for movie compatibility, and, of course,
23.97, and 60 (etc.) P (at 720 lines). This was
further expanded by the European DVB project.
It’s all very democratic but is it necessary?
Here’s another thing. If you travel to the USA
By BOB PANK.
between the and see a movie on TV it looks horrible - and it’s
transmitted legacy not because of the jet lag. It is caused by the
man who died 160 years ago defined audio carrier and the crude ‘conversion’ from film material using 3:2
A
the track width, or gauge, of most of new NTSC colour pulldown to map 24 frames onto each 60-ish
the world’s railways. In 1822, George subcarrier - hence fields of US TV. The movement judders around
Stephenson set his Standard Gauge for complications of the and, interestingly, the locals are immune to this
the world’s first steam railway at 4 foot 8.5 59.94 field rate, drop- distortion! So much so that they even managed
inches (1.44m), to match the nearby wagonway frame timecode, etc, to standards convert a whole series of ‘Dallas’
at Killingworth Colliery. Despite Isambard that are still (shot on film) to PAL working from the 3:2 NTSC
Kingdom Brunel building the London-to-Bristol perpetuated. TV copy and sent it to the UK for transmission.
line (1838) on what he considered to be a better Unlike the railways, Staggering - literally!
2.2m ‘Board Gauge’, the Gauge Act of 1846 made the TV industry of the time, with all US soaps Mind you, Americans have a problem when
the Standard Gauge compulsory for all new and everyone’s news footage shot on the over here as our 50 Hz (exact - no further maths
railways because, as we know today, standards ‘universal standard’ - film, did not see a big required) TV looks flickery to them. Here we
are a good thing. demand for going between these two standards ‘convert’ movies by running them at 25 Hz for
However, you could argue that quite a few which were, after all, separated by the Atlantic TV. This looks fine but makes the UK video
things have changed since 1822 - diesel and Ocean. The industry diverged and the standards version of Titanic nearly eight minutes shorter
electric traction, more people, faster trains, longer conversion business was born. than the screen version... or the juddery US TV
distances, better suspension, and so on. There you The good quality spatial interpolation needed version. I feel the industry’s head is in the sand.
hit the downside of standards; they can stymie to go between different picture sizes (eg 525 and Surely, if you have a competent frame rate
development and perpetuate legacy. Probably the 625-line) has, for many years, been well within converter you can make a good job of turning 24
Killingworth track gauge was something to do TV engineering capabilities. However high motion picture film to 60 Hz video? I would find
with horses and carts - some even blame the quality conversion between frame rates is far that far better than the old 3:2, but maybe the
Romans! But at least these early influences were more tricky and can never be perfect. For locals would shun it as not having the ‘movie
directly to do with transport. Why then should a example, when going from 50 to 60 Hz, every look’. Surely not! And why shouldn’t movie
modern audiovisual communication system run fifth input frame coincides with every sixth material for the UK and Europe be frame-rate
at the speed of something seemingly totally output frame; the other five frames between have converted to 25 Hz to suit its TV? I don’t know
unrelated: the frequency of mains power? to be synthesised from the adjacent input frames, what the value of eight minutes of blockbuster is
Of course, back in 1936 when the BBC started or fields. This gets increasingly difficult as objects to TV, but it must be worth quite a few beers in
transmitting the state-of-the-art ‘high-definition’ move around the screen, so genres such as live the IBC2009 pub.
television system with 405 lines (a big advance sports are often challenging for conversion, Certainly standards and associated frame rates
on the previous 30!), there was a good reason to whereas period dramas are generally easier. are continuing to multiply with the latest for HD
lock the picture frequency to the 50 Hz mains. TV Current top-of-the-range modern frame-rate being 50P for Europe and 60P, or 59.94P, for the
set power supplies of the day were not that good, converters use motion compensation processing USA. The 60P footage I’ve seen is amazingly
so locking the picture to main frequency meant techniques based on motion vectors that track the good. Maybe we should all unite under a highest
that any resulting video ‘hum bar’ would be objects within the pictures and so know where to common frequency with 60, yes 60, Hz
static, not rolling down the screen, and so not put them in the output pictures. It’s as good as it progressive for all HD and film - SHV is already
very noticeable. Following the same reasoning gets and some experts say they can’t see any using it. Or it maybe precisely because today
the USA chose 60 Hz frame rate to sync its 525- errors in material output from the very best people know very good frame rate conversion is
line system with its power. This was subsequently converters. Even so, why not avoid this and have available that they feel free to move between
multiplied by 1000/1001 to steer around crosstalk a universal Standard Frame Rate? standards - without fear of going off the rails!
16 IBE NOVEMBER/DECEMBER 2008
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