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Objectives - Quality vs. Reliability

At the time of writing, HEVC/h.265 is beginning to emerge more fully in production. By far h.264 is still the dominant compression technology for distribution models. However, h.265 does produce a higher quality for a given bitrate than h.264, so it has a place in contribution technology. That said, bandwidth in most venues is these days nowhere near as scarce as it was 15 years ago when I used to have to channel bond multiple ISDN lines to create a 384k connection out to the CDN from many venues. Today, one can expect conference centers to have 10Mbps to 100Mbps leased line connectivity - but you must always check and confirm this beforehand, ensuring that any firewall access is in place.

Why am I discussing this under quality vs. usefulness?

If the site has a 5Mbps connection, you are in a marginal range. Normally it is good practice to deliver two copies of your contribution feed to your CDN - one feed to two diverse locations so that should one fail, the other will give the event continuity. Allowing a little overhead to 2Mbps contribution streams would be using pretty much all of that 5Mbps connection. Should something else happen to unexpectedly try to stream 2Mbps over that same link (as so often happens at facilities where multiple people have access to the IP link), then both contribution feeds may suffer from network congestion.

At that point one there are a few options:

  • • Increase the budget and upgrade to a 10mbps link.
  • • Downgrade the contribution feed quality to 1.5Mbps (etc.) to provide more overhead for the unexpected.
  • • Drop one of the two contribution feeds and hope nothing goes wrong with it, since that would produce a blackout.

Ultimately all webcasts need to undertake this risk/link budget assessment to properly define how reliably the event will be delivered. As budgets become constrained, these outcomes and risk indicators come strongly into play.

Granted, it is not strictly true to say that in a bandwidth-constrained environment that “reliability is inversely proportional to quality" but it is a good rule of thumb to have in mind.

 
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