1080i - WHY is that native for most if not all "HDTV channels"? - Page 3 - AVS Forum
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post #61 of 73 Old 01-29-2012, 05:30 PM
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Originally Posted by TVOD View Post

I also worked many centuries ago on the plexiglass headed monster that the above controller connected to. The joys of sticking a screwdriver through small openings to drop the heads on large fast spinning discs, often times in cramped quarters and not the cleanest environments.

The HS-100 was one of the earliest examples of video recording on a disc. And it was (of course) analog. Only certain people were deemed worthy to lower the heads onto the disc. Did you ever have to send out for good vodka to clean the heads/disk?
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post #62 of 73 Old 01-30-2012, 02:02 AM
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Yep - the HS-100 is one of the first, but was a good few decades after the first recordings of TV to disc.

http://www.tvdawn.com/tv1strx.htm This is a link to the Phonovision recordings made by Baird in the 1920 and 30s. Amazing to think that within a few years we went from 30 line mechanical TV to a fully electronic 405line interlaced 50Hz system which continued until the mid-80s. (After launching in 1936)
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post #63 of 73 Old 01-30-2012, 07:33 AM
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OK, maybe I should have said electroninc television disc recording...

Baird's system is probably more like the RCA SelectaVision CED discs in 1981. Then there was the LaserDisc from 1980. Arvin made a system that could store 200 stills on a magnetic "disc" around 1976, I think.

Mechanical television is still pretty amazing. They sometimes have a demonstration of it running at the Early Television Museum in Hilliard, Ohio (near Columbus, Ohio) in the USA.

In any case, I don't think the Baird Phonovision discs would make for good slow motion
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post #64 of 73 Old 01-30-2012, 06:54 PM
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I just bought my first CED player a few weeks ago! More of a curiosity than anything. The picture is pretty good. Better than your average VHS, but it can't touch laserdisc's 425 lines of resolution. (CED tops out at 240.)

Here's the place for everything CED.

http://www.cedmagic.com

Former USSB uplink operator.
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post #65 of 73 Old 01-30-2012, 07:25 PM
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Originally Posted by hphase View Post

The HS-100 was one of the earliest examples of video recording on a disc. And it was (of course) analog. Only certain people were deemed worthy to lower the heads onto the disc. Did you ever have to send out for good vodka to clean the heads/disk?

At stadiums we usually had to settle for what was available at the vendors, which was usually what was ever on tap, before doing any work on it ... oh wait I think you meant something different

Looking back it's amazing how reliable how such a vulnerable design was, especially as it was mainly used for field work. Of course once in a while there were failures, to which the notification was given "The slo-mo is no mo".

I know this is getting OT, but one thing I remember that was kind of funny was the commonly used informal name given to the full sized TV81 camera cable. No one thought anything of it at the time. As the cable was rather thick because it was multicore, it was referred to using a rather course term which described a male horse's anatomy. I don't think that would fly in current times. It was often just abbreviated to "horse".


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post #66 of 73 Old 01-30-2012, 08:23 PM
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Originally Posted by scowl View Post

This was a major problem with old encoders that could only search for matching blocks in a short area around each block (usually a diamond shaped area). Now encoders are so powerful that they can do exhaustive searches of entire HD frames in real time to match blocks. They'll find that block no matter where it is.

Could it be that the 720p was an advantage to a station using an older encoder rather than buying a new one? Encoder prices have fallen to where I don't think that would be a major issue to most even with tight budgets.

Using FOX as an example, while I have noticed GOP boundaries on some football game (aka swimming grass), the amount of blocking artifacts seem far less than what I commonly see on 1080i stations even without subchannels. I know FOX uses the splicer system to avoid re-encoding, but CBS's 40 Mbs network feed should suffice as it's 2:1 of the ATSC rate. NBC is harder to compare directly as the ones I've viewed have subchannels.

It seems the argument for 1080/50p or 1080/60p encoding as requiring only slightly more bandwidth is more recent. Perhaps that is using MPEG 4.

While there are some advantages to 720p, if I had to pick one standard I would choose 1080i. Of course 8k @ 120 fps progressive with 22.2 might be nice too.


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post #67 of 73 Old 01-30-2012, 08:27 PM
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Quote:
Originally Posted by hphase View Post

Baird's system is probably more like the RCA SelectaVision CED discs in 1981.

A system that RCA (when the A stood for America) highly benefited from


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post #68 of 73 Old 01-30-2012, 09:33 PM
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Quote:
Originally Posted by TVOD View Post

Could it be that the 720p was an advantage to a station using an older encoder rather than buying a new one? Encoder prices have fallen to where I don't think that would be a major issue to most even with tight budgets.

Using FOX as an example, while I have noticed GOP boundaries on some football game (aka swimming grass), the amount of blocking artifacts seem far less than what I commonly see on 1080i stations even without subchannels. I know FOX uses the splicer system to avoid re-encoding, but CBS's 40 Mbs network feed should suffice as it's 2:1 of the ATSC rate. NBC is harder to compare directly as the ones I've viewed have subchannels.

It seems the argument for 1080/50p or 1080/60p encoding as requiring only slightly more bandwidth is more recent. Perhaps that is using MPEG 4.

While there are some advantages to 720p, if I had to pick one standard I would choose 1080i. Of course 8k @ 120 fps progressive with 22.2 might be nice too.

720p's big advantage comes on 24p content where 60% of the frames are essentially duplicates and therefore need few bits to compress. Even on a 1080i encoder that can detect and reverse pulldown (which few actually utilize in ATSC broadcasts due to problems with false detection and broken decoders), only 20% of the fields are redundant.

Fox's encoders are more aggressive about making GOP boundaries match scene changes. CBS uses NetVX encoders at most of their O&Os, and they seem to have them configured to ignore scene changes and pretty much use strict 15 frame GOPs. That does lead to some less than stellar frames for the remaining portion of the GOP when the material is challenging. Encoders that use longer, but variable-length, GOPs seem to suffer less at scene changes, but they do have a longer average delay before the picture starts decoding because of having to wait for an I frame.
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post #69 of 73 Old 01-30-2012, 10:52 PM
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Quote:
Originally Posted by TVOD View Post

It seems the argument for 1080/50p or 1080/60p encoding as requiring only slightly more bandwidth is more recent. Perhaps that is using MPEG 4.

According to the EBU it doesn't need any more than 1080i (both 1080/50p and 1080/50i using mpeg4).
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post #70 of 73 Old 01-31-2012, 04:54 PM
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Hopefully that will spur 1080p live production. However with 4K now making appearances at CES for both acquisition and display including panels and home projection, and internet increasing the share of media delivery to home with better codecs on the horizon such as h.265, I wonder if 1080p will be bypassed. I know I'm biased against JVC somewhat, but a 4k camcorder for less than $5k this year shows how fast 4k is moving. OK I know it's not an Alexa or a Red, but that's still is a significant step forward to me.

Once we get to home 4K (and especially 8k), will theaters survive? I know there are still many, perhaps even a majority, who still prefer the communal viewing experience, but for those who are growing up with high quality home viewing will that continue? Will HD be considered low-def?


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post #71 of 73 Old 01-31-2012, 05:18 PM
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Quote:
Originally Posted by TVOD View Post

Hopefully that will spur 1080p live production. However with 4K now making appearances at CES for both acquisition and display including panels and home projection, and internet increasing the share of media delivery to home with better codecs on the horizon such as h.265, I wonder if 1080p will be bypassed. I know I'm biased against JVC somewhat, but a 4k camcorder for less than $5k this year shows how fast 4k is moving. OK I know it's not an Alexa or a Red, but that's still is a significant step forward to me.

Once we get to home 4K (and especially 8k), will theaters survive? I know there are still many, perhaps even a majority, who still prefer the communal viewing experience, but for those who are growing up with high quality home viewing will that continue? Will HD be considered low-def?

The problem is the last mile to the customers set, transport via fiber or satellite with 4:2:2 mpeg-2 or DVB-S2 MPEG-4 has plenty of bandwidth available.

From the TV station or Cable company to the consumers set top is the problem...

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post #72 of 73 Old 01-31-2012, 11:08 PM
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Quote:
Originally Posted by scowl View Post

Forcing you to send twice as many of them every second including twice as many less-efficient I-frames.

I knew there was something I might have missed. Each 720p I frame represents half as many pixels as a 1080i I frame. That would cancel out having twice as many. The last P frame in the GOP would be half the time as in interlace from the I frame. The B frames would be half the time between P frames. This should provide tighter correlation between frames. Even with full frame motion search, the rate of motion doesn't usually stay consistent, and I would think that would cause a difference of the spectral content of a moving object from motion blur. Also with constant length GOPs, a worst case cut separating the P and B frames from the I frame would affect half the time and pixels compared to interlace.

Even without 2:3 detection, 720p may be more efficient than 1080i as each progressive frame represents a unique 24p frame, while in interlace there are 2 of the 5 frame sequence which contain mixed frames between the fields.


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post #73 of 73 Old 02-01-2012, 01:24 AM
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Originally Posted by ybsane View Post

The problem is the last mile to the customers set, transport via fiber or satellite with 4:2:2 mpeg-2 or DVB-S2 MPEG-4 has plenty of bandwidth available.

Yep - and nobody realistically expects MPEG2 to be used for feeds to consumers for any new platforms. The US/Japan/Aus/Korea are the odd-ones-out globally using MPEG2 for consumer broadcast of HDTV - everyone else is using H264 (aka MPEG4 pt 10/AVC)

Whether 4k and 8k use H264 or the newly developing replacement will be interesting. I suspect that 8k will need a newer compression scheme to make sense even using DVB-S2 satellite.

The demo I saw of 8k/60Hz Super HiVision over satellite used 2 x 70Mbs DVB-S2 transponders with the 8k signal sent as 16 simultaneous tiled 1080/60p H264 streams - at around 140Mbs in total. (The live camera demo used 800Mbs MPEG2 over a fibre IP connection from London to Amsterdam).

Until they can get 8k onto a single transponder (ideally more than one stream onto this) - which may already be feasible (the demo I saw was a couple of years ago) then even satellite bandwidth is still looking limited.

Of course 4k is an interesting discussion - as that is probably feasible now for premium content.

Quote:


From the TV station or Cable company to the consumers set top is the problem...

I suspect 4k/8k is likely to be fibre or satellite based to the consumer - not OTA or copper-cable based - in many territories. Cable and telco companies are eventually going to have to bite the bullet and replace copper with fibre to the consumer - as is the case in places like Japan or Korea.

I notice that at least one telco company in the UK is now fibreing new built homes and offering 50-200Mbs fibre internet connections in these properties.
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