I’ve always wondered if that was done to allow mixed video and DOCSIS channels, shared hardware on either end, or just to ensure that TVs and STBs can quickly and safely skip DOCSIS channels that they won’t be able to decode anyway.

And in those early days many cable providers didn't even implement the Baseline Privacy Interface, so you could sniff the entire neighborhood's downstream traffic with a modified modem or possibly even a DVB-C capable TV card.

There was literally a register bit in the cable modem MAC to enable promiscuous mode, and you could just set it: https://pastebin.com/18702Ziq

Sadly the Broadcom modem hardware I used to experiment with then seemed to lack the ability to get at the raw MPEG-TS packets, so I didn't manage to repurpose it as a TV receiver. The idea was to tune to a TV channel and stream it over multicast RTP on the LAN.

As used modems were very cheap, I wanted to have a whole bank of them, to demodulate every carrier on the CATV system. All fed into a giant, noisy 24 port 100Mb Ethernet switch that had IGMP snooping support. That was back in the 2000s...

Modem photo: https://www.usbjtag.com/jtagnt/ambit120.jpg

If I remember correctly, the 188-byte packets are a result of using ATM AAL-5 frames, each 53-byte frame having 5 bytes of ATM header, 1 byte of AAL-5 framing, and 47 bytes of payload (47x4 = 188).

> The new ATSC 3.0 standard (NextGen TV) in the U.S.

Don't worry. After 3 comes 4 and 5. /s

What about bridging broadcast media to IP or vice versa?

One of the advantages of MPEG-TS is that it’s dead simple to map it to RTP or even plain UDP and back even with packet loss and data errors.

"The Transport Stream is a stream definition which is tailored for communicating or storing one or more programs of coded data according to ITU-T Rec. H.262 | ISO/IEC 13818-2 and ISO/IEC 13818-3 and other data in environments in which significant errors may occur. Such errors may be manifested as bit value errors or loss of packets."

"The Program Stream is designed for use in relatively error-free environments and is suitable for applications which may involve software processing of system information such as interactive multi-media applications. Program Stream packets may be of variable and relatively great length."

> It shouldn't be used on discs (ahem Blu-ray) or other storage and it shouldn't be used over the Internet.

I thought Blu-Ray switched to program stream, but DVD was transport stream (sounds like I've got things backwards though). Transport stream for optical media isn't that insane though, because while you can seek, seeking isn't great, and if you have a failed read, it's probably better to just move on than to retry that sector a bunch of times. Of course, using transport streams allows for smaller buffers and lower BOM, so there's that too.

I use it for storage because I can stream a recording, with full seeking, while I'm actively capturing it, or I can stream it over a websocket for a little less latency.

Having one thing that works just as well as WebSockets as it does over HLS makes things a lot easier on low performance devices where a format conversion would be a bad thing.

MPEG-TS is like a virtual analog RCA jack, it's easy to understand and work with and manipulate as long as you don't have to touch the encoding or decoding stuff, and lets you do lots of odd applications.