WebRTC vs HTTP Streaming

[namast...@gmail.com]

Hi,

I've been experimenting with WebRTC and HTTP streaming protocols (HLS, MPEG-DASH) for live video streaming for a few days now, and have found that while WebRTC achieves sub second latencies, HTTP streaming protocols always have multi-second latencies. I therefore have a couple of questions related to WebRTC vs HTTP streaming. 

1. How is WebRTC able to achieve sub second latencies compared to HTTP streaming protocols?

2. If WebRTC already provides low-latency video streaming, why is there an effort to unify HTTP streaming protocols under the MPEG-DASH standard?
3. How does WebRTC compare to RTMP? (I haven't explored RTMP until now, but I want to know if it's possible to achieve sub-second latencies with RTMP)


Thanks
Bharat Khatri

[nazmus shakeeb]

Hi Bharat,

Here is my understanding. It may help you.

WebRTC uses RTP and RTCP protocol for voice and video communication. These are widely used protocols for real time voice and video communication standardized by

IETF. To minimize latency WebRTC can do the following things.

1. use UDP to send receive packet ( TCP can introduce delay )

2. discard frame 

3. change quality of the video ( depending on bandwidth )

4. send voice and video separately 

         

So when using WebRTC latency of the video can be very less.

But HTTP and RTMP are mostly used in the server to client video streaming where quality is great as 

1. It never drops frame.

2. Never changes quality on they fly.

3. Uses TCP for communication ( in fact HTTP has more overhead than TCP but quality is same ) 

but these protocol needs some buffer to show smooth video. so latency is high. 

When HTTP protocol is used it can be used by any browser ( no need of WebRTC support ).  

So both protocols are necessary. You need to select right one based on your requirements. 

Thanks,

Shakeeb

[Niels Moller]

On Tue, Aug 30, 2016 at 9:37 PM, <namast...@gmail.com> wrote:

1. How is WebRTC able to achieve sub second latencies compared to HTTP streaming protocols?

It doesn't use TCP, and it doesn't use large (1s or more) chunks of data.

 

2. If WebRTC already provides low-latency video streaming, why is there an effort to unify HTTP streaming protocols under the MPEG-DASH standard?

HTTP streaming has its place for streaming without low-latency requirements. And it works nicely with HTTP caching infrastructure.

3. How does WebRTC compare to RTMP?

No idea.

 

/Niels