One cable is not another cable. The ability to transfer at speed is highly dependent on the sensitivity and characteristics of the electrical signals, how they are transferred, the characteristics of the cable, the transmitter, and the receiver. High speed TTL signals are designed to be transferred only a few cm. It works in a pinch yeah. Works great testing too. But it is not in any way "good", and by that I mean anything from causing poor performance to potentially interfering with other components in your design. Also what works on the bench is not necessary what works in the living room when someone takes your final product and does whatever it is they do with it using whatever poor crap they found laying in the bottom of their drawer. For transmission over any distance you universally never use TTL signals. It does not work over any appreciable distance, and I can't stress this enough: it was tried and failed which is precisely why I2S is converted to LVDS before being sent over HDMI in practice.OK, yes I guess I needed an other coffee and was completely off with the frequency. Lot of things in what you say make sense, but not enough to say "cant work". Cables can transport much higher speed, and well, as I said, Developpers do this all the time, connecting 2 boards together with I2S. As for Jitter, sorry I didn't get your point. Why exactly it's intrinsyncly worst? You don't have to define the incoming I2S clock as the master clock as for autodetect nothing that can't be done. I agree this is Frankensteinish as of now but I don't see any of this as a fatality.
It's no different to the serial connections from the 80s. USART is TTL, it was designed to transmit over very short distances. As soon as you wanted to connect a printer you would use RS-232 instead with its 15V instead of 5V and short circuit protection.
Speaking of protection, you're completely missing the human aspect here too. I2S is designed to be permanently connected and terminated between chips. Datasheets give you instructions of what to do with unconnected inputs and outputs in your design. They are also not in any way designed to be floating and disconnected, and simply the act of walking across the room and touching the connector can potentially fry your DAC chips. I2S affords no protection against short circuit, over voltage, incorrect connection, static electricity, etc, etc. Quite different from an LVDS transmitter or receiver.
To your last point I now don't get your point. If you're not defining the incoming clock as the master clock when using I2S then I really ask what you're hoping to achieve. I2S's only benefit as a connection is its clocking. If you're not going to use it then why go through this pointless exercise? Why Frankenstein together something in a way it was never designed to be used when you're not going to use its main marketable benefit it affords over the common and well defined S/PDIF or AES3 standard?
Also I say "marketable" because the benefit certainly isn't measurable.
No that's not the cost of standardisation. That's the cost of certification and licensing. You can create a USB device for free, you're just not allowed to market it as USB or display the USB logo on it. And while you point to USB as a costly standard, I could point you to hundreds of others which are completely free, e.g. every serial standard used RS-232, RS-422, RS-485, ... errr wait, how about I2S (it is after all a standard when used correctly).Standardisation ACTUALLY adds cost, you know that a licence to have a USB port is about 4K a year?
Not having seen something doesn't mean it doesn't exist. Companies themselves are very clear that there's zero guarantee that I2S will work. They don't say this because they like to advertise their features in this way. They say this because they there's no formal standard. You're right about one thing *IF* the port works, it works. But that "IF" is precisely what standards seek to resolve.If the port works, the port works. If there is a formal standard or just a casual agreement, what does it matter? I haven't seen posts saying, "I2S doesn't work!" I have been seeing posts complaining about some violated aesthetic engineers hold dear.