Live Streaming to Browser

Question

I'm a bit at my wits end here.

I want to stream a live video broadcast to a web browser.

Currently I use ffmpeg to stream a directshow live source as a webm stream to node.js which then forwards the stream to the http request from the <video> element. So far everything works.

live source -> ffmpeg -> POST [webm] -> node.js -> GET [webm] -> video tag

My problem is that the source clock and the web clients clock doesn't exactly match each other (not that surprising). For video this is not a problem, dropping or duplicating a frame every now and then is not noticeable. However, with audio it is another issue. From what I've been able to figure out so far Chrome (or any other browser) does not perform any form of audio resampling compensation (e.g. swr_set_compensation from ffmpeg) to compensate this mismatch. Instead I get quite audible audio distortions (a loud beep) when the playback buffer runs out of samples.

My question is whether it is possible to achieve proper playback (with audio) of a live source in a web browser?

I haven't tried using silverlight or flash for playback yet. Would that possibly work better?

Answer 1

Live media (audio or/and video) streaming to a web browser has been possible for a couple of years though it is still making progress as of today. It is the next big thing for media on the web and many platforms like Youtube are already on board.

A typical live media streaming scenario is:

audio/video feed > transcoding > streaming > player

At each step you have several technological possibilities available. However I should already mention here that the road to live media streaming is paved with proprietary technologies.

• audio/video feed: either raw or very lightly compressed media format and cannot be uploaded as such to the Internet. You need to transcode it. You may have to use a grabbing device like a PCI Express card or USB/thunderbolt device to get your cam onto a computer.
• transcoding: you have software (ffmpeg, Flash media live encoder, Wirecast) or hardware solutions (streamingmedia.com has a wealth of information on the subject like here). H264/AAC is the current media professional standard and streams are often transcoded to multiple renditions (bitrate) to suit different network conditions.
• streaming: you most likely need to target multiple devices to deliver your live stream. Not all devices support the same streaming protocol. HLS works on Apple devices and Android > 4.1. HDS or RTMP works in Flash, Smooth streaming in Silverlight. You cannot reach all devices with one protocol so in this case you would need a streaming server like Wowza or Red5. A streaming server take as an input a transcoded live stream and prepare it for cross device delivery while sustaining a massive number of simultaneous connections (over a thousand is not uncommon nowadays). It can also add functionalities like DVR or DRM. As of today the effort is around HTTP adaptive bitrate delivery. Large companies add CDN support for global delivery.
• player: to display your live stream with various options like custom layout, closed captions, ads, chat module and more. Flash has been leading the market up until now for live media streaming on desktop. You can use HTML5 video for iOS and Android where HLS is supported.

Coming in fast is MPEG DASH and it works live with HTML5 video. There is a JS lib that supports live. I have tested it and it works though I may not use it for a production case scenario just yet as it is still a bit clunky (on demand support is better) and browser support is narrow at the moment (As of 8/30/13, Desktop Chrome, Desktop Internet Explorer 11, and Mobile Chrome Beta for Android are the only browsers supported).

I cannot comment much on your solution because I have not used node.js for streaming but it sounds like an interesting effort. A typical solution I would use relating to your case:

Device > ffmpeg (H264/AAC) > Wowza > Hybrid player (Flash + HTML5).

Instead of Wowza you could use Red5 (free/open source - but not much activity as of late). You can also look into Nginx RTMP module which supports HLS and MPEG DASH on top of RTMP.

For flash I use Strobe from Adobe which support live streaming and is easy to set up and a fallback to HTML5 where flash is not supported. I use SWFObject lib to detect flash support and feed a HLS URL to an HTML5 video tag for mobile devices. You can use RTSP for Android < 4.1 and other mobile devices.

Another thing I should mention is real time communications. For video/audio conferencing you could have a look at WebRTC. Those 2 articles should get you on the right track. Here and here. WebRTC will work great for one to few, one to one, few to few. If you need to support more concurrent connections you can have a look at Licode or tokbox.