Show HN: Boltstream – Self-hosted full end-to-end live video streaming platform

In broadcast contribution, where you have someone in the studio talking to a person on the screen, anything over a second brings complaints. Typically aim for under 500ms of processing delay for low bitrate contributions, and at 25fps with a bog standard blackmagic card going SDI-IP-SDI, and add in timing, you're looking at 500ms of your budget eaten by the hardware framebuffer. OBE do a better capture card - one which allows access to the data on a line by line basis. If you go for something more hardware based and say a J2K codec you can get your latency down to a couple of frames.

I had a problem a few years ago with lives from Kiev -- the ISP we had kept dropping our packets for 125ms at a time. Didn't matter if we sent 20mbit (so 2000 packets per second) or 2mbit (200pps), the number lost in a row matched the 125ms outage.

Network people laugh when I complain about 125ms outages on the internet, but it meant that standard FEC wouldn't work (maximum of 20 burst packets, even if it recovered every lost packet that would mean errors above a transport stream rate fo 1.6mbit.

Now you can use RIST to dial in resends, but with a 100ms rtt you're looking at needing 300-500ms of buffer to cope with that type of outage (to realise the packets are missing and not just delayed (say 50ms), to ask for the retransmit (50ms), and to get them (50ms, then smear them over time as you can't do an instant retransmit)

Alternatively you can transmit twice and offset, but that still adds 150ms of delay.

(SRT itself is a defunct file transfer protocol that's had some life brought back into it by Haivision)

Big broadcasters tend to go for "open standards" from groups like SMPTE and DPP. The "DPP001 - Live IP Profile" recommendation has a variety of different profiles depending on the importance of the media and the network that's involved, but it generally revolves around MPEGTS over RTP, with either dual streaming (sending the same packets down two different networks), or RIST (so a NACK based error correction), or perhaps both. Certainly when I broadcasted major international TV events recently, I've gone for both RIST and two networks.

The last thing you want is your signal to drop out for 10 seconds due to a power failure while your network reroutes just as the final touchdown at the superbowl happens - or worse in the the commercials.

In the world cup in 2018 I was watching an RTP feed direct from the IBC in Moscow on my desktop in VLC. The goal went in, and strangely I recognised it was a goal for England (I don't really do football). Window was open, and I cheered.

A few seconds later the neighbours cheered - they were watching it on TV.

I remember watching a 4K FA Cup final too in parallel to an off air TV feed. Watched the goal go in on the TV. By the time it had gone in on the 4K feed I'd actually forgotten it was a goal, so I guess that wasn't too bad.

That's a problem with streaming. If you're watching a popular live event like a big football match, and your neighbours are too, you need to be receiving it at the same time to avoid "spoilers".

If you stream speedrun attempts, a block of ads every 30 minutes probably isn't going to cause viewers to miss anything of significance, so it's probably safe to flip that switch. Of course, when the ads show up at the wrong time in that case, it's probably very upsetting.

But if you stream a show with banter between hosts, and you already manually run ads every hour while preparing for the next segment of the show, and you still get interrupted in the middle of the dialogue by an ad? That's horrible.

If you stream a competitive game (DotA, LoL, Overwatch, Warzone, etc), and your amazing comeback from behind gets interrupted by an ad, you're going to lose both short term and long term revenue.

Long term because viewers will get frustrated and leave. Short term because viewers seeing a great play are more likely to donate and gift subscriptions to celebrate the moment. But if they don't actually see it, you can't get that hype train started, and you lose out and so does Twitch.