[vlc-devel] will streaming protocols survive OR will http become the protocol of choice?!

[Rémi Denis-Courmont]

Le Tuesday 29 January 2008 21:29:29 Marc E. Fiuczynski, vous avez écrit :
> I've been playing a bit with VLC using both the client and server
> components of RTSP, and am excited to see the recent submitted patches
> on supporting client-side RTMP.  I'm just curious what the developers of
> VLC consider the longevity of (legacy) RT*P streaming protocols.  It
> seems that one can do everything (except multicast) via HTTP.
> Specifically, the perceived benefits of streaming protocols (e.g., RTSP,
> RTMP) are to the best of my knowledge:
>
> 1) security (users cannot easily save a stream to disk)

> 2) trick play (seek to arbitrary points)

> 3) lower bandwidth utilization
>
> None of those benefits hold any more, as one can now:
>
> 1) easily save streams to disk using various media players,

RTSP is not "easy" to save, but it is doable, and would become easier if there 
was more demand.

> 2) trick play is now supported either through the use of HTTP range
> queries or on the server side via a CGI (see youtube), and

Assuming you know where to seek. Yes.

> 3) http servers designed for delivering multimedia "just in time"
> (versus ASAP bulk downloads) in ways that mirrors what streaming
> protocols (again a simple experiment with youtube reveals that they pace
> the outgoing data delivery).

Even if the server does not pace, the client could do it at TCP level. This is 
not really an issue. The only use is to rate limit clients.

Probably the main reason why RTSP mostly failed so far is that it is so 
unfriendly to NATs and firewalls. Hence people come with non-compatible 
solutions, and there is no big incentive to interop. Also companies want to 
sell and buy proprietary solutions for media...


For video-on-demand, where you may actually want to have big receive buffers 
and reliable reception, it is actually better to use HTTP than RTSP. And then 
you get firewall and NAT traversal as an added bonus. So yeah, I don't see 
much point in using more dedicated protocols, such as RTSP there.

As far as I can tell, the one and only real advantage of UDP (beyond 
multicasting) is low latency. But you typically don't care so much about 
latency when streaming, as you would when conferencing.

You can argue whether TCP (HTTP) is good or bad for live streaming (not VoD) 
then, but obviously VoD is much more common an usage.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
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