I have written at length about what ABR is and what are its pros and cons, you can find some extracts in the links at the end of this post. I'll try here to share my views and expose some facts to enable a more pragmatic approach.
I think we can safely assume that every actor in the mobile video delivery chain wants to enable the best user experience for users, whenever possible.
As I have written in the past, in the current state of affair, adaptive bit rate is often times corrupted in order to seize as much network bandwidth as possible, which results in devices and service providers aggressively competing for bits and bytes.
Content providers assume that highest quality of content (1080p HD video for instance) equals maximum experience for subscriber and therefore try and capture as much network resource as possible to deliver it. Browser / apps / phone manufacturers also assume that more speed equals better user experience, therefore try to commandeer as much capacity as possible. The flaw here is the assumption that the optimum is the product of many maxima self regulated by an equal and fair apportioning of resources. This shows a complete ignorance of how networks are designed, how they operate and how traffic flows through these networks.
An OTT cannot know why a user’s session
downstream speed is degrading, it can just report it. Knowing why is important
because it enables to make better decisions in term of the possible corrective
actions that need to be undertaken to preserve the user’s experience. For
instance, a reduction of bandwidth for a particular user can be the result of
handover (4G to 3G or cells with different capacity), or because of congestion
in a given cell or due to the distance between the phone and the antenna or
whether a user enters a building, an elevator, or whether she is reaching her data
cap and being throttled etc.… Reasons can be multiple and for each of them, a
corrective action can have a positive or a negative effect on the user’s
experience. For instance, in a video streaming scenario, you can have a group
of people in a given cell streaming Netflix and others streaming YouTube.
Naturally, the video streamed is in progressive download adaptive bit rate
format, which means that the stream will try to increase to the highest
available download bit rate to deliver the highest video definition possible.
All sessions will theoretically increase the delivered definition up to the
highest available or the highest delivery bit rate available, whichever comes
first. In a network with much capacity, everyone ramps up to 1080p and everyone
has a great user experience.
More often than not, though, that
particular cell cannot accommodate everyone’s stream at the highest definition
at the same time. Adaptive bit rate is supposed to help there again by stepping
down definition until it fits within available delivery bit rate. It
unfortunately can’t work like that when we are looking at multiple sessions
from multiple OTTs. Specifically, as soon as one player starts reducing its definition
to meet lower bit rate delivery, that freed-up bandwidth is grabbed by other
players, which can now look at increasing even more their definition. There is
no incentive for content provider to reduce bandwidth fast to follow network
condition, because they can become starved by their competition in the same
cell.
The solution here is simple, the delivery of ABR video content has to be managed and coordinated between all providers. The only way and place to provide this coordination is in the mobile network, as close to the radio resource as possible. [...]
This and more in my upcoming Mobile Edge Computing report.
This and more in my upcoming Mobile Edge Computing report.
Part I:What is ABR?
Part II: For ABR
Part III:Why isn't ABR more succesful
Part IV: alernatives
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