120hz versus 240hz
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From: Dave Plowman (News) on 2 Mar 2010 05:04 In article <7v3f4mFldkU1(a)mid.individual.net>, Phil Allison <phil_a(a)tpg.com.au> wrote: > "Geoffrey S. Mendelson" > > > > The 50 and 60 fields per second (a field being half an interlaced > > frame) were chosen not because they needed to be that fast (48 would > > have done), but to eliminate interefence effects from electrical > > lights. > ** But the lights concerned were those being used to illuminate the TV > studio. Studio luminaries are commonly filament lamps. To allow easy control of level, and because of their continuous spectrum light output. > When frame rates are not locked to the AC supply frequency, faint > shadows can be seen moving up or down studio images on a monitor or > home TV set - due to the twice per cycle dip in brightness of > incandescent lamps. In the UK TV hasn't been mains locked for about 40 years. I'd guess other countries the same. The mains frequency varies too much for modern requirements. > Other fixes include using lamps with sufficient thermal inertia or > groups of lamps on different phases to eliminate the light modulation. Fluorescent types are used on location these days, but use high frequency ballasts. HID types don't run at mains frequency either. Only time I've seen a phased array used was for a boxing ring - before high frequency ballasts became common. -- *I pretend to work. - they pretend to pay me. Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: Arfa Daily on 2 Mar 2010 06:37 "Dave Plowman (News)" <dave(a)davenoise.co.uk> wrote in message news:50f1a111e3dave(a)davenoise.co.uk... > In article <td_in.163148$Dy7.138444(a)newsfe26.ams2>, > Arfa Daily <arfa.daily(a)ntlworld.com> wrote: >> The digital terrestrial TV being provided here in the UK now, currently >> carries no HD content, despite ongoing promises. > > Not so. BBC HD is transmitted on FreeView as is ITV HD. CH4 and 5 will be > added shortly. This is from the London transmitter. Not sure about > everywhere. > > -- > *Who are these kids and why are they calling me Mom? > > Dave Plowman dave(a)davenoise.co.uk London SW > To e-mail, change noise into sound. None available on FV here in my east midlands location. Just looked at my "TV Times" (national) listings mag, and it claims that BBC HD is available on Freesat CH 108, Sky CH 143 and Virgin Cable CH 108. Likewise, it says that ITV HD is only available on Freesat via the 'red button' service. In any case, BBC HD is hardly a useful service, as they just stick a mixture of their total network output on there at random times. I was recording "Survivors" on BBC HD via sat on series link. Suddenly, the series finale has disappeared from the recording list. I check the schedules, and it's just not on there. Some random olympics programme or something. So I hastily set it to record on SD BBC. Then, a couple of days later, it randomly appears again on BBC HD at some obscure time when they had a slot to fill. ITV HD, from what I've seen of it on the Freesat service, seems to be just for football matches, once in a while. Either service is hardly inspiring for people with HD TV sets and a built-in DTTV tuner, as most have. So I would have to conclude that at the moment, the London area is possibly unique in carrying these services. Just as a matter of interest, what equipment is required to receive these FreeView HD transmissions, and has the compression scheme now been finalised then, to allow manufacturers to produce necessary equipment in bulk ? Interesting that you say that CH5 is shortly going to be placing HD content onto FreeView. At the moment, they have no HD output at all, and I would have thought that if they were about to start, then the first places would have been on the Sky satellite service, and Virgin cable, where there is an existing customer base, with fully operational equipment to allow them to access and view the service. Channel Four I can understand wanting to provide a FreeView service as they already produce an HD mirror of their SD service on Sky and Virgin. Just as a matter of interest, do you know what cameras they use for producing their HD content (or their programme makers / suppliers) ? Just that their HD output is stunningly good compared to some other efforts by other stations. And I'm talking original 'native' HD here, not just content that was shot in standard res, and then placed on the station's HD channel. Taking, for instance, Phil and Kirsty's "Relocation, Relocation" (Wednesday 8pm) programme on CH4. The image quality is absolutely cracking, and everything you would expect HD to be. Likewise, "Extreme Engineering" on NatGeo I think it is, and "American Chopper" on Discovery. OTOH, "Lost" and "24" from Sky 1 both claim to be 'originals' in HD format, but although they look better in HD than they do in SD, they still seem to lack that 'pin-sharp' quality that the other programmes I've cited, have. As you are 'in the business' so to speak, just wondered if you had any insights into this ? Arfa
From: William Sommerwerck on 2 Mar 2010 08:49 > I'm not sure what exactly you mean by "an evolving standard". > That seems an oxymoron if ever I heard one. Either it's a standard, > or it's an evolving system. It can't be both. To the best of my understanding, all audio and video codecs carry with them the information need to correctly decode the transmission. This allows (for example) DVDs and Blu-rays to use varying bitrates and different codecs. (If this isn't right, please correct me.)
From: Dave Plowman (News) on 2 Mar 2010 08:53 In article <mM6jn.192295$4D2.36704(a)newsfe12.ams2>, Arfa Daily <arfa.daily(a)ntlworld.com> wrote: > "Dave Plowman (News)" <dave(a)davenoise.co.uk> wrote in message > news:50f1a111e3dave(a)davenoise.co.uk... > > In article <td_in.163148$Dy7.138444(a)newsfe26.ams2>, Arfa Daily > > <arfa.daily(a)ntlworld.com> wrote: > >> The digital terrestrial TV being provided here in the UK now, > >> currently carries no HD content, despite ongoing promises. > > > > Not so. BBC HD is transmitted on FreeView as is ITV HD. CH4 and 5 will > > be added shortly. This is from the London transmitter. Not sure about > > everywhere. > None available on FV here in my east midlands location. They're really just tests at the moment. The full HD service should be available by the Olympics next year. > Just looked at > my "TV Times" (national) listings mag, and it claims that BBC HD is > available on Freesat CH 108, Sky CH 143 and Virgin Cable CH 108. > Likewise, it says that ITV HD is only available on Freesat via the 'red > button' service. Well, I don't have a FreeSat receiver but get ITV HD off satellite. > In any case, BBC HD is hardly a useful service, as > they just stick a mixture of their total network output on there at > random times. I was recording "Survivors" on BBC HD via sat on series > link. Suddenly, the series finale has disappeared from the recording > list. I check the schedules, and it's just not on there. Some random > olympics programme or something. So I hastily set it to record on SD > BBC. Then, a couple of days later, it randomly appears again on BBC HD > at some obscure time when they had a slot to fill. With just the one HD service, choices will be made. > ITV HD, from what > I've seen of it on the Freesat service, seems to be just for football > matches, once in a while. Some dramas too. The most regular being The Bill. > Either service is hardly inspiring for people > with HD TV sets and a built-in DTTV tuner, as most have. I'd be surprised if many have an HD set with a built in HD tuner - they've only just been announced. And an ordinary Freeview tuner won't get HD. > So I would have to conclude that at the moment, the London area is > possibly unique in carrying these services. Just as a matter of > interest, what equipment is required to receive these FreeView HD > transmissions, and has the compression scheme now been finalised then, > to allow manufacturers to produce necessary equipment in bulk ? FreeView HD tuners are on the market. But I'll not get one until there's a HD PVR at a reasonable price. > Interesting that you say that CH5 is shortly going to be placing HD > content onto FreeView. At the moment, they have no HD output at all, > and I would have thought that if they were about to start, then the > first places would have been on the Sky satellite service, and Virgin > cable, where there is an existing customer base, with fully operational > equipment to allow them to access and view the service. The relationship between Sky and its audience is based on making Sky money. Nothing to do with providing a service. > Channel Four I can understand wanting to provide a FreeView service as > they already produce an HD mirror of their SD service on Sky and Virgin. > Just as a matter of interest, do you know what cameras they use for > producing their HD content (or their programme makers / suppliers) ? > Just that their HD output is stunningly good compared to some other > efforts by other stations. And I'm talking original 'native' HD here, > not just content that was shot in standard res, and then placed on the > station's HD channel. Taking, for instance, Phil and Kirsty's > "Relocation, Relocation" (Wednesday 8pm) programme on CH4. The image > quality is absolutely cracking, and everything you would expect HD to > be. Likewise, "Extreme Engineering" on NatGeo I think it is, and > "American Chopper" on Discovery. OTOH, "Lost" and "24" from Sky 1 both > claim to be 'originals' in HD format, but although they look better in > HD than they do in SD, they still seem to lack that 'pin-sharp' quality > that the other programmes I've cited, have. As you are 'in the > business' so to speak, just wondered if you had any insights into this ? I'm not sure what gear is used for the progs you mention. But the snag is some still use filters to soften the image - especially with 'talent' of a certain age who don't want every wrinkle to show. Near always on drama. However, anything shot outdoors to look good is likely to look particularly sharp due to the light levels than drama, etc. The HD drama I work on uses Thompson cameras and is recorded on Panasonic P2 - memory card based system. The pictures are quite superb - until the fog filters go in. ;-( -- *Corduroy pillows are making headlines. Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: Geoffrey S. Mendelson on 2 Mar 2010 11:04
William Sommerwerck wrote: > To the best of my understanding, all audio and video codecs carry with them > the information need to correctly decode the transmission. This allows (for > example) DVDs and Blu-rays to use varying bitrates and different codecs. (If > this isn't right, please correct me.) No. It's much more complicated than that. AVI files carry imformation about the file, such as a codec number each for audio and video, the bit rate, the frame rate, number of audio channels, and so on. Satellite (and DBS) data feeds contain some information, some feeds contain none at all. DVD's, Blu-Ray, VCD's, etc, all have a very specific format. DVD's are also limited to MPEG-2 video encoding (with a limited range of resolutions, frame rates, etc.) They also have a very limited range of audio encoding. Sometimes it amazes me that a program such as mplayer or VLC can play a random file and it works. The reason the Chinese DVD players can play so many files now is that they either use the freeware Linux based player, Mplayer, or the proprietary clone of it written in a language for embedded systems. Just as an example, someone gave me a sample of the files created by their DVB-T TV decoder. They are raw MPEG-TS files, encoded with H.264 and AAC. Nothing I have can open them. :-( Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm(a)mendelson.com N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |