3 ms·

I find it hilarious (in a mildly sad way) that NTSC (or any other analog system) is a far better system for final delivery when conditions aren't effectively pe

by LocalH 4y ago

I find it hilarious (in a mildly sad way) that NTSC (or any other analog system) is a far better system for final delivery when conditions aren't effectively perfect. Guarantee you that a digital broadcast will break down far before any analog broadcast will. If only digital could be used for 99% of distribution, with OTA still being at least some sort of hybrid system for better resilience. Digital broadcasting has very low resilience to interference. Speaking from a US perspective here, where we got saddled with 8VSB (from my understanding, COFDM is much more resilient).

iso1631 4y ago
That's not right. Digital transmission systems will cope with the errors and regenerate a perfect signal upto a point called the digital cliff. With that amount of noise in an analog signal will be a very snowy, staticy, picture. In an analog signal, a bright picture will be 700mV, a less bright picture will be 500mV, a dark one at 200mV and a very dark one at 50mV. Imagine that you get a 300mV error, that loses a lot of data - the dark one will be sort of bright, or vice versa, or the sort-of bright will be really-bright, etc. Now lets say you have a 1 represented by an amplitude of 700mV, and a 0 represented by 50mV. A 300mV error wlll have it at 400mV and 350mV. Your system will go "hey this is 350mV, it's a zero", and reclock it to 50mV, and vice versa. The recovered signal will be identical upto the point that the errors flip the bits - the digital cliff. (In reality of course the signal isn't just high/low but uses various techniques to encode the ones and zeros to prevent DC voltages accruing - Manchester Encoding for example. Push an analog video signal down a cable and it will degrade the longer the cable is. The same will happen in the digital domain -- you can see this on a waveform monitor by looking at the digital eye, but as long as the eye is open enough the signal can be retrieved to it's original state. With an analog signal, the signal is lost, and can't be retrieved.
- LocalH 4y ago
  Like I said, part of my gripe is really with 8VSB, and not digital OTA in general. At least in the US, digital OTA signals break down far quicker into an unwatchable state than analog (analog might be snowy and staticy, but our brains are wonderful at poking through that and understanding the content).

by LocalH 4y ago

iso1631 4y ago

That's not right. Digital transmission systems will cope with the errors and regenerate a perfect signal upto a point called the digital cliff. With that amount of noise in an analog signal will be a very snowy, staticy, picture. In an analog signal, a bright picture will be 700mV, a less bright picture will be 500mV, a dark one at 200mV and a very dark one at 50mV. Imagine that you get a 300mV error, that loses a lot of data - the dark one will be sort of bright, or vice versa, or the sort-of bright will be really-bright, etc. Now lets say you have a 1 represented by an amplitude of 700mV, and a 0 represented by 50mV. A 300mV error wlll have it at 400mV and 350mV. Your system will go "hey this is 350mV, it's a zero", and reclock it to 50mV, and vice versa. The recovered signal will be identical upto the point that the errors flip the bits - the digital cliff. (In reality of course the signal isn't just high/low but uses various techniques to encode the ones and zeros to prevent DC voltages accruing - Manchester Encoding for example. Push an analog video signal down a cable and it will degrade the longer the cable is. The same will happen in the digital domain -- you can see this on a waveform monitor by looking at the digital eye, but as long as the eye is open enough the signal can be retrieved to it's original state. With an analog signal, the signal is lost, and can't be retrieved.

LocalH 4y ago
Like I said, part of my gripe is really with 8VSB, and not digital OTA in general. At least in the US, digital OTA signals break down far quicker into an unwatchable state than analog (analog might be snowy and staticy, but our brains are wonderful at poking through that and understanding the content).