| General > General Technical Chat |
| How do text messages travel from one phone carrier to another? |
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| Lord of nothing:
--- Quote ---FaceTime --- End quote --- what ever that is. :scared: Normally you have "HD Voice" who is mention before. The work perfect. :-+ There are some good Explanation Video from CCC and Defcon who explain how a 2G,... Network work include how the Voice Codeq work. |
| tooki:
FaceTime is like Skype, except with better audio/video quality! It’s too bad there’s no indication of whether a given phone call is using HD voice or not — I have a hunch we don’t notice when it’s working, but of course we do notice when we have a bad connection. |
| Lord of nothing:
Some have, do, show: https://www.google.com/search?q=hdvoice+icon&num=100&client=firefox-b&source=lnms&tbm=isch |
| johnh:
With VoLTE over 4G Codec choice is negotiated between devices. Either a handset or Media Gateway The network might strip/remove some codec choices by manipulating the SDP, in the INVITE and response in 200OK The media gateway can used to perform trans-coding, this a last choice because of the performance penalty of trans-coding. |
| Zbig:
As this thread has already diverted to codec quality, bandwidth and compression, I remember how surprised I was back in the day upon learning at school about the concept of "comfort noise". Apparently, in digital communications devices, there was an audible background noise artificially injected locally by the user's terminal equipment (telephone). Turns out people would get confused when, in the periods of both talking parties going silent, the line would go totally silent as well. They were so used to the poor quality of analogue telephony and its inherent background noise that they would associate the noise with the connection ongoing. In order to save time and/or bandwidth, the equipment was gating the audio signal (passing it through only once its level has exceeded some arbitrary threshold) and inserting the locally-generated artificial static during the pauses. I remember how outraged my teenage geek self was at the idea or "ruining" the clear, digital signal path deliberately so it could sound as bad as POTS. If memory serves, 2G cellphones, DECT phones were all doing that, among others. I'm not sure I'm not imagining this now but I think I even saw an option to disable or enable the comfort noise in a VOIP gateway device. Fast forward some twenty years, I have both VoLTE and VoWiFi available with my telco and on my phone. While the improvement in quality is apparent and very welcome, I have more than once found myself going like "Hello? You still there?" when the person I was talking to went silent for a while. It was then when it dawned on me that I can no longer hear any "comfort noise" during the pauses in our conversation. That's why I now wonder: is the comfort noise feature now being omitted on purpose? Have they arrived at the conclusion that the new generations don't need it anymore as they don't remember/weren't born in the era of analogue telephony and it's time to abandon the idea? Or is it the negligence/incompetence on the device manufacturer's part? Are the codecs/standards specific in the topic of whether to use comfort noise or not? |
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