> Which smartphones block call recording? Every brandname Android I have had enables this feature for voice calls. (Although the feature is missing for app calls, and I'm now at least 5 years behind the newest phones.)

This explains a lot because this is a more recent development. https://www.pcmag.com/news/google-is-banning-call-recording-...

As the article says it was blocked a couple years ago but there was still a loophole which is now being closed as well. Though it's by blocking apps using it from the play store which can still be avoided by sideloading so technically there still is a loophole :) But it's definitely seeing more and more restrictions.

In some cases there might be local laws involved. If you buy a Samsung (or LG, but they don't make phones anymore) in Korea it will come with call recording available.

Might be, though all places I went had services stating upfront they record the call, so recording in itself wasn't illegal.

The main issue is that neither Google nor Samsung seem to understand European law on this point - it is blocked by both of them in Europe, presumably because of GDPR, but any lawyer who claims that GDPR prevents an individual for recording their own phone calls locally for personal use would get laughed out of the room.

Except at Google and Samsung apparently. And there's no way to contest this decision for users, query it or even get a straight answer out of either company on it.

> Which smartphones block call recording?

iOS?

I'm not sure of the current state of Android but back in the early days this feature also wasn't there (there were tons of apps that claim to do it but they all exploited some device-specific quirk and wouldn't work universally) despite the hardware being capable of doing this from day 1.

The reason call recording is shunned is that tons of scummy companies would suddenly end up in trouble if call recording becomes widespread and accessible to anyone.

Not just scummy companies…. Politicians, cops, judges, bureaucrats, managers, bankers, and so on. Corruption is endemic in our world, and these laws are there to protect that status quo.

It might have something to do with the high fidelity voice calling having a reasonably large bandwidth that you could theoretically use as a data channel - many times larger than an old v.92 modem. Maybe that's not so relevant these days with more people having unlimited data plans.

Why would the phone manufacturer care?

(And in any case, as you suggest most people pay more per bit transmitted on a mobile voice call than they pay per bit as data.)

Purely for fun, it would be interesting to hack up two smart phones to transmit data over a voice call. Presumably, you can keep everything binary, if you control the end-points.

That's how SMS works. It's running a baseband modem over the voice channel.

SMS is transmitted over digital signaling or transport channels. There was never any analog coding involved (except for a few retrofitted implementations on landlines in Europe).

That would give you a 128 kbit/s channel under absolute ideal conditions (the maximum bandwidth supported by the EVS codec).

Practically, you‘d be better off using a throttled (after exceeding the included data volume) native data connection.

I see. Yeah pretty terrible.