xinjinmeng (![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
xinjinmeng) wrote2020-04-11 11:03 pm
xinjinmeng) wrote2020-04-11 11:03 pm
Anachronistic 4K
Question from the Internet:
What was the first date at which all the trans-Atlantic Internet communication running at full bandwidth at once would have technically had the capacity to stream a 4K video from some single point to some other overseas point, in real time, if all Internet communication was dedicated to the purpose and we had 4K video encoding/decoding?
Do you mean 4K UHD, 4K DCI, or some other 4K spec? Let's assume 4K UHD.
In May 2007, NHK performed a live broadcast of UHDTV, using a custom codec that compressed video to 180-600 Mbit/s and audio compressed to 7-28Mbit sec. Since Wikipedia declares that this broadcast quality to be UHD, we will use 187Mbit/s as our smallest acceptable speed.
An analog phone line, assuming perfect quality with a 4Khz signal, could transmit 0.056 Mbit/s/line using PCM v.92. Assuming hardware that could perfectly synchronize 3,340 phone lines, it would be possible to meet this data transfer load. The first transatlantic land line, TAT-1 from 1956, only had 72 speech circuits. Data on exactly how many transatlantic cable lines existed, and when, proved impossible to find.
By May 1989, PTAT-1, a transatlantic fibre-optic cable, was operational, with 27 DS-3 channels of 45 Mbit/s. Networked together, these would be able to handle the data load with plenty to spare.
What if we went to satellite instead? Going back to NHK, the ISDB-S standard was created after 1996 to broadcast via satellite, allowing for 51 Mbit/s over a single satellite TV channel. We would only need 4 UHF channels to get our bandwidth.
The SYNCOM IV network (Leastat) would be four working satellites each capable of a single UHF broadcast, which is our minimum. This network would not have our minimum count of four channels until January 9, 1990... so PTAT-1 would beat this system by nine months and would be far, far more practical. (While Leasat would launch a fourth satellite in 1985, it failed to communicate and was never implemented. Another working satellite wouldn't appear until 1990. And let's be practical: all four satellites must be above horizon for both sender and receiver, a six-body problem that would be a logistics nightmare if not an impossibility.)
In conclusion, UHD-TV could theoretically have been broadcast over the Atlantic using PTAT-1 in May 1989, using codec technology first fielded in 2007.
_____________
Sources
https://en.wikipedia.org/wiki/Ultra-high-definition_television#2006%E2%80%932010
https://en.wikipedia.org/wiki/TAT-1
https://en.wikipedia.org/wiki/Telstar_1
https://en.wikipedia.org/wiki/ISDB#ISDB-S
https://history.nasa.gov/satcomhistory.html
https://en.wikipedia.org/wiki/Syncom#Syncom_IV_(Leasat)
https://en.wikipedia.org/wiki/PTAT_Systems
What was the first date at which all the trans-Atlantic Internet communication running at full bandwidth at once would have technically had the capacity to stream a 4K video from some single point to some other overseas point, in real time, if all Internet communication was dedicated to the purpose and we had 4K video encoding/decoding?
Do you mean 4K UHD, 4K DCI, or some other 4K spec? Let's assume 4K UHD.
In May 2007, NHK performed a live broadcast of UHDTV, using a custom codec that compressed video to 180-600 Mbit/s and audio compressed to 7-28Mbit sec. Since Wikipedia declares that this broadcast quality to be UHD, we will use 187Mbit/s as our smallest acceptable speed.
An analog phone line, assuming perfect quality with a 4Khz signal, could transmit 0.056 Mbit/s/line using PCM v.92. Assuming hardware that could perfectly synchronize 3,340 phone lines, it would be possible to meet this data transfer load. The first transatlantic land line, TAT-1 from 1956, only had 72 speech circuits. Data on exactly how many transatlantic cable lines existed, and when, proved impossible to find.
By May 1989, PTAT-1, a transatlantic fibre-optic cable, was operational, with 27 DS-3 channels of 45 Mbit/s. Networked together, these would be able to handle the data load with plenty to spare.
What if we went to satellite instead? Going back to NHK, the ISDB-S standard was created after 1996 to broadcast via satellite, allowing for 51 Mbit/s over a single satellite TV channel. We would only need 4 UHF channels to get our bandwidth.
The SYNCOM IV network (Leastat) would be four working satellites each capable of a single UHF broadcast, which is our minimum. This network would not have our minimum count of four channels until January 9, 1990... so PTAT-1 would beat this system by nine months and would be far, far more practical. (While Leasat would launch a fourth satellite in 1985, it failed to communicate and was never implemented. Another working satellite wouldn't appear until 1990. And let's be practical: all four satellites must be above horizon for both sender and receiver, a six-body problem that would be a logistics nightmare if not an impossibility.)
In conclusion, UHD-TV could theoretically have been broadcast over the Atlantic using PTAT-1 in May 1989, using codec technology first fielded in 2007.
_____________
Sources
https://en.wikipedia.org/wiki/Ultra-high-definition_television#2006%E2%80%932010
https://en.wikipedia.org/wiki/TAT-1
https://en.wikipedia.org/wiki/Telstar_1
https://en.wikipedia.org/wiki/ISDB#ISDB-S
https://history.nasa.gov/satcomhistory.html
https://en.wikipedia.org/wiki/Syncom#Syncom_IV_(Leasat)
https://en.wikipedia.org/wiki/PTAT_Systems