Archived from groups: alt.video.digital-tv (
More info?)
Stephen Neal wrote:
>>>>>IIRC, 576p is defined as HDTV in Australia.
>>>>
>>>>Since the article states lack of available content is one of the
>>>>problematic issues, it's a no-brainer that switching to 60hz (1080i,
>>>>720p) would facilitate the change, enabling immediate HDTV telecasts
>>>>of increasing portions of current and ongoing American programing,
>>>>which I'm aware is very popular in the UK.
>>>
>>>Err - the 50/60 issue is a non-issue. A lot of US drama is shot
>>>1080/24p isn't it - which we have no problems watching in 576/50i,
>>>576/25p, 1080/50i etc. with the 4% speed-up we are used to when
>>>watching 24fps film material. We don't have the 24p/60i 3:2 pulldown
>>>problem either, as 24p/50i can be done 2:2 with the speed-up.
>>
>>The speedup can work havoc with an elaborate soundtrack. While pitch
>>is no longer an issue for digital audio, a 4% speedup can drastically
>>alter the character of any music. It is correct, however, that most
>>US dramas (and comedies) are shot at 24fps and still more on film
>>than video.
>
> Given that we've put up with the speed-up on 24p material since about 1936,
> when we launched our 50i TV system (405/50i), I think we're used to it in
> the UK. With digital pitch correction the 4% speed-up is normally not an
> issue. I agree it changes the nature of music programmes - but these are
> often shot 60i or 50i rather than 24p so there is no speed change (as a
> standards conversion rather than speed change is used)
>
>>>Similarly the UK HDTV material shot 1080/25p is slowed down for the
>>>US market and run as 1080/24p (or then 3:2ed to 1080/60i)
>>
>>This has been done for a few movies shot on digital PAL (eg, "The
>>Anniversary Party"), but I've never heard of UK TV shows being slowed
>>down for US telecasts.
>
> The BBC series Rockface was shot 1080/25p on HDCam and was co-produced with
> a US broadcaster/studio. The 25p material was slowed to 24p for the US
> transmissions. (Presumably it was then either broadcast 24p or 60i with 3:2
> pull-down)
>
> I imagine that UK drama shot 25p will follow this model of slow-down to 24p.
> Of course 50i drama will still be converted to 60i with no speed change.
Most of the standards concersions I've seen were very obviously done
with the field/frame interpolation which takes portions of one
field/frame and puts it into another, which always creates ghosting and
other artifacts. While this can be minimized by additional processing,
the result is a much softer picture, and usually (though I don't
understand why) desaturated and otherwise poor color.
>>>Where frame rate conversion is required (say from 60i/p to 50i/p)
>>>standards convesion is improving now to the point where 50->60 and
>>>60->50 conversion is more transparent than MPEG2 encoding... (i.e.
>>>more motion artefacts are introduced by the MPEG process than the
>>>conversion) Using phase correlation techniques especially means it
>>>is not a major issue.
>>
>>I'm very skeptical re standards conversions because I've seen so many
>>that looked atrocious.
>
> They have got massively better in recent years. You get what you pay for.
> In the last 3 or 4 years the Snell and Wilcox Alchemist PhC and Platinum
> conversions approach transparency - even on fast moving sports.
>
> We also have the problem in the UK of having to un-pick 3:2 pull-down of US
> film transfers, as the non-continuous movement confuses motion tracking,
> instead the 3rd redundant field has to be detected and removed. So we go
> from 60i 3:2 to 48i 2:2 using DEFT (Digital Electronic Film Transfer -
> another S&W technique) and then speed up to 50i. It works really well on US
> film drama edited on 480/60i tape. You only notice the slight softness
> difference between 480 and 576 - which is far less obvious than the 3.58NTSC
> vs 4.43PAL softness difference.
>
>>After all the effort to restore "Brideshead Revisited" the NTSC
>>broadcasts (and DVDs) were literally unwatchable.
>
> Well the broadcasts will have been made on 1980s converters. I'm
> disappointed that the DVDs were standards converted at all - AIUI Brideshead
> was shot and edited on film so could have been telecined from the film
> masters to 480/60i or 480/24p for DVD mastering. You'd have probably had a
> slow-down if this were the case as I suspect the UK TV production will have
> been shot 25fps film rather than 24fps (as in Europe film-for-TV is normally
> shot at 25 rather than 24)
>
> The chances are that if the DVD was mastered from the UK VT transfer it may
> well have been the 1980s 1" C format PAL, and the telecine-ing would have
> happened in the 80s as well, if it were mastered from the US broadcast
> masters made in the 80s it will have had a pretty bad conversion as well I
> imagine. Telecine and conversion technology has moved on a-pace since the
> 80s and even the mid 90s...
>
> There are of course all the usual DVD mastering annoyances as well - too
> much noise reduction, excessive compression and addition aperture correction
> etc.
I'm fairly sure the NTSC discs were new conversions (the color was
improved, and identical to the new PAL discs). For some reason they
were just done incredibly badly. I got the PAL discs when they became
available and they are fine.
The R1/NTSC discs, though, are appalling for the unending chop-chop
arising from sub-mediocre frame/field interpolation, especially for
moderate pans and rolling credits.
>>Ditto for the new "Forsyte Saga" (though the PAL DVDs for this were
>>pretty bad too).
>
> Again - a commercial DVD release - presumably not optimised for quality.
> There seem to be a massive range in quality of UK DVD releases - the good
> ones are very good, the bad ones are terrible. The best feature film
> transfers are sourced from 1080/24p HD masters - which are converted to
> 576/50i (576/25p) via scaling and speed-up.
>
> For high quality R1 PAL video and film DVD remastering the Dr Who
> Restoration Team have worked marvels. They use a BBC R&D PAL decoder to
> transfer the D3 copies of the 2" or 1" video masters (which leaves almost no
> composite artefacts), and where possible re-transfer and re-grade any film
> inserts that remain as film in the BBC archive. The quality is often
> stunningly good.
I've noted that the quality of PAL discs seems to vary a lot, and I've
been disappointed often by the discs for UK TV series.
As you say, most movies now are mastered at 1080/24, which makes for
easy downconversion to NTSC and PAL specs.
>>>>576p requires nothing more than display devices with line-doubling
>>>>and perhaps frame doubling (to 100hz) capacity.
>>>
>>>576/50p requires at worst 576/50p acquisition gear - which is rare.
>>>I think it is more common to shoot 1080/50i and then downconvert to
>>>576/50p, or 1080/25p frame doubled? Of course you can also TK 25fps
>>>film (sped up 24fps film as well) to 50p by frame doubling. There is
>>>no advantage over 576/25p, but an improvement over 576/50i if you
>>>don't vertically filter to reduce interlace twitter.
>>
>>I'd assume that with proper conversion to progressive scan, this
>>should work.
>
> 576/50i to 576/50p should be OK if the de-interlacing processing is high
> enough quality. 576/50i to 576/25p will look horrid though, as you are
> chucking away half of the motion information. To reduce display flicker
> then you would either have to move to 576/100p (quite a high scan rate) or
> 576/100i (which will have some interlace artefacts - but these will be at
> 50Hz not 25Hz as is the case with 50i)
>
>>>>This has been available from Faroudja for several years.
>>>
>>>Faroudja are more in the display conversion rather than standards
>>>conversion business aren't they? Snell and Wilcox have made HD
>>>standards converters (and some of THE best SD converters) for a
>>>while.
>>
>>Faroudja is best known for its high-end home scalers (I have one of
>>their NRS series feeding 720p/60 to an Ampro HD3600 CRT projector)
>>and, more recently, the FLI2310 chip used in certain progressive-scan
>>DVD players (with scaling to 720p and 1080i as well as 480p).
>
> Yep -scaling rather than conversion - i.e. the field/frame rates are not
> changing? (Apart from 24 to 60 which is a 3:2 conversion rather than
> anything more complex?)
>
> In other words scalers used to get between 480i to 480p to 720p to 1080i at
> either 30 or 60 (or 24 with 3:2)
Faroudja scalers rescale all NTSC sources to 60 frames. For 24fps
source material, the additional field generated by the 3:2 pulldown is
discarded, a progressive frame is created by combining the two fields
from each movie frame, and the result is output at 60fps, reinstating
the pulldown but eliminating all interlace artifacts.
> If we were to move to 60i, 60p or 30p production in Europe we'd need to use
> field/frame rate tstandards conversion, rather than scaling, permanently to
> convert to or from 576/50i for upconversion of SDTV material, and
> downconversion of HD. Whilst this is now a high quality process it is also
> a much more expensive process than scaling - especially if you have to do it
> for all of your outlets, especially regional ones. Far better to only
> field/frame rate convert the small amount of imported material rather than
> your entire archive and continued SDTV production base?
>
> Given that much of what the UK would import from the US would be 24p, rather
> than 30p or 60i, that would be easily converted to 48i then sped up to 50i
> for playout without conversion. We'd then only need to do a standards
> conversion for the 30p, 60i or 60p material such as sport, gameshows etc.
> which are far less common and popular imports than the 24p stuff.
I realize we can't expect broadcast networks to shange their ways, but
there is no reason for serious home theater people to be short-changed.
Ideally all video sources should be displayed in their original format.
>>>>I've heard mixed comments re the 100hz TVs sold in Europe.
>>>
>>>This is because they are mainly used to convert 576/50i to 576/100i
>>>- with no real progressive conversion. Some (Philips Natural Motion)
>>>even convert material (like film) sourced 576/25p, but broadcast
>>>576/50i, to 576/100i by interpolating in-between fields, giving the
>>>whole film sequence a really fluid "video" look. Very disconcerting
>>>- and the total opposite of what many producers are now doing
>>>(shooting video at 576/50i but reducing the temporal resolution in
>>>post-production to 576/25 to give a "film" look)...
>>>
>>>One problem is that it is difficult to buy a direct view CRT set with
>>>external 576/100i or 1080/50i inputs in the UK - so you are
>>>dependent on the internal processing architecture - and can't chose
>>>your own.
>>
>>Has their been much interest in progressive-scan DVD players in the
>>UK?
>
> Not huge amounts - though quite a few players are available. However there
> are very few 50p CRT sets on the market. Prog scan DVDs are mainly used
> with inherently progressive display devices that can't display interlace
> native - plasmas, DLPs, LCDs etc - which have 576/50p input compatibility.
>
> However the vast majority of TV sales in the UK are still direct-view CRTs -
> predominantly in the sub 28" diagonal. However increasingly >21" sets sold
> are 16:9 CRT shape - it is very difficult to buy a 4:3 set bigger than 21"
> in most UK stores these days. 32" is the largest mass market 16:9 CRT -
> though 36"ers are now on offer.
>
> Plasmas are growing in popularity, though like projectors they are still
> quite niche.
>
>>I'm aware of them being marketed but, as you say, without compatible
>>displays their use would be limited.
>
> 100i rather than 50p is the marketing thing for direct-view CRTs in the UK.
> Annoying as I would rather watch an unprocessed 50i picture - but it is
> difficult to buy a high-end TV without processing to 100i now... (And only
> the higher end sets have multiple RGB inputs etc.)
>
>>>>Obviously they would eliminate the flicker
>>>>associated with 50hz; however, if the rescaling (especially for
>>>>interlace-video sourced material) is not done well the results might
>>>>be less than stellar.
>>>
>>>The interpolation, motion compensation/tracking etc. used to
>>>generate twice the number of fields is the real problem with
>>>European 100Hz sets. You get smearing on fast motion, nasty overly
>>>vicious noise reduction, enhancement of MPEG2 blocking and HF
>>>artefacts etc. introduced on DVD, DSat and DTT transmissions. The
>>>RGB interconnects commonly used between DVD / Digital TV set top
>>>boxes and European TVs means that some of the MPEG2 artefacts that
>>>would be hidden by PAL (or NTSC) composite or S-video encoding
>>>aren't - so you see more of the coding errors.
>>
>>Rescaling is always a balancing act. If the source is technically
>>poor it will likely look worse on a high-resolution display.
>
> Yep - though a lot of 100Hz introduces as many artefacts as it also exposes!
>
>>If new display formats eliminate flicker associated with PAL (even
>>NTSC) and do so without compromising other technical aspects this is
>>the way to go IMO.
>
> Technically the flicker is nothing to do with PAL - that is only the chroma
> standard!
>
> I think you have to divorce your display rate and your broadcast rate don't
> you?
>
> I think that we'd be best suited eventually moving to 1080/25p and 1080/50p
> broadcast standards - display on direct CRTs would be at 100i (with
> interlace artefacts at 50Hz) - but display on plasma, DLP, LCD etc would be
> at 50p without major flicker (as the flicker is more a CRT scanning raster
> thing which isn't inherent in other display technologies?)
>
>>Someone has even suggested a 120hz standard for American HDTV which
>>would be fully compatible with both legacy 60hz NTSC video and all
>>movies and 24fps film-sourced TV series (for which each frame would be
>>shown five times, eliminating 3:2 pulldown artifacts).
>
> Yep - presumably retaining 24p and 60i/p transmission systems and only
> up-converting to 120p or i in the display device by frame repetition?
Exactly. Movies would be should with each frame repeated five times.
NTSC sources would be line doubled and frame doubled.
>>My major issue with 50hz standards is the excess flicker for standard
>>displays, and the fact that all movies and film-sourced American TV
>>series must be speeded up which may cause serious audio compromise.
>
> Have you watched 50i or 25p material on a non-CRT device?
No, only on my Sony PVM monitors, all of which are multistandard.
> The audio
> compromise is only an issue for the small amount of imported stuff we have -
> our native stuff has none. The major UK networks show quite small amounts
> of imported material - though feature films I agree are compromised
> slightly, but I personally find 3:2 more annoying than the audio change!
Feature films IMO are very seriously compromised, and this is my primary
objection re 50hz.
Assuming a multiscan display can be available, my ideal DVD player
would, first, rescale all NTSC and PAL movies to 720p using Faroudja
technology; second, discard the pulldown for NTSC and the speedup for
PAL and output a 72fps display; third, restore the audio for PAL discs
to their correct speed using a digital chip.
C.