Re: [media-and-entertainment] Use of WebRTC for media content distribution (#1)

> ATSC is an IP Multicast system. What do you consider the "real Internet"? Is ATSC a fake system?

I consider the real internet to be a network of networks that permit me to use TCP/IP or UDP/IP to access a remote systems.

IP multicast depends on packet switching. Most importantly for IP multicast is the correct forwarding of packets to an interested subscriber, generally achieved using Layer 3 routers or Layer 2 switches (with snooping) in path between sender and receiver. For better or worse, the internet is heterogenous in so far as different access network technologies, operator domains and many other factors. Such IP networks may carry unicast and multicast traffic, which can interfere with each other with negative consequence. To this end there are several approaches to deployment, for example, some IP multicast deployments prevent interdomain multicast (so-called multicast islands), some will segment the unicast and multicast networks (i.e. seperate VLANs).

Please explain how OTA broadcast delivery of IP packets satisfies IP multicast expectations.

Can you point me towards an ATSC-compliant ROUTE transport endpoint on a publically routable IP address such that I can test out without needing to be in the OTA broadcast coverage area?

>>    I was part of the DVB analysis and disagree with your statement. The conclusions of ATSC are not applicable to heterogenous IP networks.

>ATSC is heterogenous. Unicast transport is fully integrated into ATSC along with IP multicast. Your premise is not accurate.

"Heterogenous networks" i.e. networks composed of multiple: vendors, operators, physical layer technologies etc. ATSC seems not to support heterogenous networks if I can't access it using one of the many IP standards-compliant clients at my disposal.

> Again - ATSC does porivde both unicast and multicast modes of delivery. Please familiarize yourself with the specification before making such statements.

I know ATSC provides both. What I've seen and heard is that the "multicast mode" is independent of the unicast mode. This is distinct from DVB mABR which relies of the combination of modes e.g. unicast IP is used for service discovery and fast-channel change, multicast IP is used for bulk transfer of ABR resources such as segments of audio, video or subtitle tracks.  DVB mABR relies on an access network route into the internet.

So to your earlier point that "Any broadcast transport must have clear identification of the necessary information included in a RAP (Random Access Point), in order to allow for fast channel acquisition. This includes: broadcaster application for the channel, initialization segment" the DVB design avoids these design constraints - such information is discoverable via unicast IP access. If that is also the case for ATSC, then your earlier comment is invalid. Which is the case?

-- 
GitHub Notification of comment by LPardue
Please view or discuss this issue at https://github.com/w3c/media-and-entertainment/issues/1#issuecomment-441160305 using your GitHub account

Received on Friday, 23 November 2018 05:48:19 UTC