We develop an IP camera product which streams H.264/MPEG4/MJPEG video via RTSP/UDP. It has a web interface, currently we use the VLC Firefox plugin to allow viewing of the live RTSP stream in the browser but Firefox are dropping support for NPAPI plugins so that's currently a dead end.

The camera itself is a relatively low-powered ARM SoC (think Raspberry Pi level) so we don't have vast spare resource to do things like transcode streams on-the-fly on the board.

The main purpose is to check the video stream is working correctly from the web interface, so streaming a new stream (or transcoding it) in some other format/transport/streaming engine is less desirable than being able to somehow play the original RTSP stream directly. In regular use the video is streamed via RTSP into a VMS server so that's not up for alteration.

In an ideal world the solution would be open-source cross-browser and happen inside an HTML5 tag, but if it works in one or more of the most popular browsers we'll take it.

I've been reading all sorts of stuff here and around the web about the brave new world of the HTML5 video tag, WebRTC, HLS, etc. and have yet to see anything that looks like a sensible and complete solution that doesn't involve some extra conversion/transcoding/re-streaming, often by some half-supported framework or an extra server in the middle which is not a viable solution.

I haven't yet found a proper description of what may or may not be required to "convert" our stream to whatever-html5-video-likes, whether it's just a slightly different wrapper around the same basic video stream or if there's a lot of overhead and everything is different. Likewise it's not clear if the conversion could be achieved either on-board or perhaps even in-browser using JS.

The reason for the title is that if we've got to change the way it all works we may as well aim to do whatever is considered "best practice" and reasonably future-proof as far as possible rather than some expedient fudge that might not work beyond the next round of browser updates / the next W3C press release...

I find it slightly disappointing (but perhaps not surprising) that in 2017 there seems to be no sensible way of achieving this.

Perhaps "least worst practice" would be more suitable terminology...

There are many methods you can use that don't require transcoding.

WebRTC

If you're using RTSP, you're much of the way there in sending your streams via WebRTC.

WebRTC uses SDP for declaring streams, and RTP for the transport of these streams. There are some other layers you need for setting up the WebRTC call, but none of these require particularly expensive computation. Most (all?) WebRTC clients will support H.264 decoding, many with hardware acceleration in-browser.

The easiest way to get started with WebRTC is to implement a browser-to-browser client first. Then, you can go a layer deeper with your own implementation.

WebRTC is the route I recommend to you. NAT traversal (in most cases) and P2P connectivity are built-in, so your customers won't have to remember IP addresses. Simply provide signalling services and your customers can connect directly to their cameras at home from wherever. Provide TURN servers, and they'll be able to connect even if both ends are firewalled. If you don't wish to provide such services, they're lightweight and can run directly on the camera in a mode like you have today.

Fragmented MP4 over HTTP Progressive with `<video>` tag

This method is much simpler than WebRTC, but totally different than what you're doing now. You can take your H.264 stream, and wrap it directly in an MP4 without transcoding. Then, it can be played in a <video> tag on a page. You'll have to implement the appropriate libs in your code, but here's an FFmpeg example that outputs to STDOUT, which you'd pipe to clients:

ffmpeg \
  -i YOUR_CAMERA_HERE \
  -vcodec copy \
  -acodec copy \
  -f mp4 \
  -movflags frag_keyframe+empty_moov \
  -

Others...

In your case, there's no added benefit to DASH. DASH is intended for utilizing file-based CDNs for streaming. You control the server, so there's no point in writing out files or handling HTTP requests in a file-like manner. While you can certainly use DASH with H.264 streams without transcoding, I think it's a waste of your time.

HLS is much the same. Your stream is compatible with HLS, but HLS is dropping out of favor rapidly due to its lack of flexibility on codec. DASH and HLS are essentially the same mechanism... write a bunch of media segments to a CDN and create a playlist or manifest indicating where they are.