[streaming] Re: Multicast streaming and forward error correction...

[Marshall Eubanks]

Hello;

Multicast UDP is no less reliable than unicast UDP, while streaming  
TCP has its own issues.

However, if you are really serious about this, you need to  
investigate applying FEC.
RMT FEC has been accepted by MBMS and other other mobile services, and
Digital Fountain has an implementation (I do not know about open  
source implementations).
I can certainly get you in touch with DF principals if you want their  
code and API.

If you have access to the actual wireless links, investigate adding  
or tweaking the transport layer FEC.
I believe that most wireless systems support this, and it would  
probably be cheaper and, of course,
it applies to everything on the link.

Regards
Marshall

On Feb 22, 2006, at 9:12 AM, Chhaya, Harshal wrote:

>
>> Any help at all would be appreciated, including any other help with
>> streaming multicast on a wireless link! :)
>
>
> James,
>
> I don't think VLC supports FEC for transmitting a stream but I don't
> know for sure and I will let others comment on that.
>
> But I do know that streaming multicast on a wireless link is less
> reliable than streaming unicast on the same link. The wireless LAN
> protocol requires explicit acknowledgement for unicast data which
> helps with re-transmissions of lost frames. This re-transmission is
> very quick and is transparent to the upper protocols (TCP/UDP).
> Multicast/broadcast data are not acknowledged and so lost frames
> can't be recovered quickly. And if you are using UDP to stream, they
> can't be recovered at all. As a result, streaming multicast video
> over a wireless link will suffer from packet loss.
>
> Have you tried sending each video as a unicast stream? If the total
> data-rate can be supported by your wireless link, this could be your
> best option.
>
> Regards,
> - Harshal
>
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