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Most video streams degrade gracefully when data is corrupted. Losing a byte or two is (generally) not that big of a deal. Encryption turns every dataloss into

Most video streams degrade gracefully when data is corrupted. Losing a byte or two is (generally) not that big of a deal. Encryption turns every dataloss into something catastrophic. Now, instead of 1 byte lost, you are talking about 1 mb lost (or whatever the size of the encryption chunks are). That becomes especially bad as codecs get more bandwidth friendly. That 1mb can represent a lot of data, which ultimately gets corrupted until the next keyframe flows through. You can sort of think of it in terms of a bitmap vs jpeg. If you corrupt 40 bytes in a 1mb bitmap, no problem, it will still mostly look like the original image. However, if you turn that bitmap into a 30kb jpeg and corrupt 40 bytes, now that's a much more significant amount of the information changed.

bobdvb 3y ago
The block cipher used on broadcast doesn't have a big impact. People have been doing encryption on pay TV broadcasting for decades. There's also plenty of error correction, often 25% of the broadcast feed data is ECC.
- cogman10 3y ago
  Like I said, it expands the amount of data lost when corruption does happen. You can't have 1 bit off. And, due to the nature of interference, it's generally a block of bytes that end up corrupted. Encrypted pay tv exists (in the form of satellite transmissions) but there, interference is minimized by having a geosynchronous satellite high in the air directly beaming a signal. Only bad weather interferes. Further, because it's being beamed from a single source (rather than multiple towers around an area). you can point your dish directly at the satellite to get a relatively perfect directional connection. Other signals, the sun, power lines, etc don't generally interfere because you are concentrating a focused signal. That math all changes when talking about receiving multiple terrestrial signals with a non-directional antenna. If you've watched satellite tv, you know that whenever a storm rolls through it becomes unwatchable. There's not really any sort of graceful degradation, it's either a perfect signal or a blank screen with "no signal". SOMETIMES you might see giant swaths of green blocks or whatever if the corruption is just right, but generally speaking it's all or nothing. Meanwhile, I get relatively weak signals from a couple of weak OTA stations. For the most part, the images are perfectly passable.

bobdvb 3y ago

The block cipher used on broadcast doesn't have a big impact. People have been doing encryption on pay TV broadcasting for decades. There's also plenty of error correction, often 25% of the broadcast feed data is ECC.

cogman10 3y ago
Like I said, it expands the amount of data lost when corruption does happen. You can't have 1 bit off. And, due to the nature of interference, it's generally a block of bytes that end up corrupted. Encrypted pay tv exists (in the form of satellite transmissions) but there, interference is minimized by having a geosynchronous satellite high in the air directly beaming a signal. Only bad weather interferes. Further, because it's being beamed from a single source (rather than multiple towers around an area). you can point your dish directly at the satellite to get a relatively perfect directional connection. Other signals, the sun, power lines, etc don't generally interfere because you are concentrating a focused signal. That math all changes when talking about receiving multiple terrestrial signals with a non-directional antenna. If you've watched satellite tv, you know that whenever a storm rolls through it becomes unwatchable. There's not really any sort of graceful degradation, it's either a perfect signal or a blank screen with "no signal". SOMETIMES you might see giant swaths of green blocks or whatever if the corruption is just right, but generally speaking it's all or nothing. Meanwhile, I get relatively weak signals from a couple of weak OTA stations. For the most part, the images are perfectly passable.