[vlc-devel] vlc: svn commit r21814 (jb)

[Damien Fouilleul]

Rémi Denis-Courmont wrote:
>> raw UDP is still used to feed EdgeQAM through a local network, where 
>> packets reordering is not a problem, so dropping this is a mistake
>>     
>
> The idea that there can be no reordering on a local network is an urban
> myth. There might be trunking/bonding for instance.
> Or you might even have reordering on loopback if you use some packet
> schedulers.
>
> As far as I know, we do not have any muxer that supports reordering,
> so you are essentially broken if you use raw UDP.
>
>   
In the absolute, I don't disagree with you. Unfortunately, when you feed 
hundreds MPTS or SPTS to an EdgeQam, i.e gigabits of data, out of order 
packets just cannot be reordered and are just dropped, the local network 
must be configured in such a way that packets are routed in a 
predictable matter (ever heard of MPLS ?). Anyway, in those conditions, 
RTP does not provide any advantage over raw UDP. btw, in most cases, 
RTP's advantage isn't really about reordering, but timestamping, as late 
packets can be dropped early by any router in a the network path, thus 
avoid unnecessary congestion in low bandwidth networks, such as GPRS, etc...