Lets review the problems experienced by ABR that hinder its penetration in the market.
1. Interoperability
Ostensibly, having three giants such as Apple, Adobe and Microsoft each pushing their version of the implementation leads to obvious issues. First, the implementations by the three vendors are not interoperable. That's one of the reason why your iPad wont play flash videos.Not only the encoding of the file is different (fMP4 vs. multiplexed), but the protocol (MPEG2TS vs. HTTP progressive download) and even the manifest are proprietary.This leads to a market fragmentation that forces content providers to choose their camp or implement all technologies, which drives up the cost of maintenance and operation proportionally.MPEG DASH, a new initiative aimed at rationalizing ABR use across the different platforms was just approved last month. The idea is that all HTTP based ABR technologies will converge towards a single format, protocol and manifest.
2. Economics
Apple, Adobe and Microsoft seek to control the content owner and production by enforcing their own formats and encoding. I don't see them converge for the sake of coopetition in the short term. A good example is Google's foray into WebM and its ambitions for YouTube.
4. Content owners' knowledge of mobile networks
Adaptive bit rate puts the onus on content owners to decide which flavour of the technology they want to implement, together with the range of quality they want to enable. In last week's example, we have seen how 1 file can translate into 18 versions and thousand of fragments to manage.Obviously, not every content provider is going to go the costly route of transcoding and managing 18 versions of the same content, particularly if this content is user-generated or free to air. This leaves the content provider with the difficult situation to select how many versions of the content and how many quality levels to be supported.
As we have seen over the last year, the market changes at a very rapid pace in term of which vendors are dominant in smartphone and tablets. It is a headache for a content provider to foresee which devices will access their content. This is compounded by the fact that most content providers have no idea of what the effective delivery bit rates can be for EDGE, UMTS, HSPA, HSPA +, LTE In this situation, the available encoding rate can be inappropriate for the delivery capacity.
In the example above, although the content is delivered through ABR, the content playback will be impacted as the delivery bit rate crosses the threshold of the lowest available encoding bit rate. This results in a bad user experience, ranging from buffering to interruption of the video playback.
5. Tablet and smartphone manufacturers knowledge of mobile networks
Obviously, delegating the selection of the quality of the content to the device is a smart move. Since the content is played on the device, this is where there is the clearest understanding of instantaneous network capacity or congestion. Unfortunately, certain handset vendors, particularly those coming from the consumer electronics world do not have enough experience in wireless IP for efficient video delivery. Some devices for instance will go and grab the highest capacity available on the network, irrespective of the encoding of the video requested. So, for instance if the capacity at connection is 1Mbps and the video is encoded at 500kbps, it will be downloaded at twice its rate. That is not a problem when the network is available, but as congestion creeps in, this behaviour snowballs and compounds congestion in embattled networks.
As we can see, there are still many obstacles to overcome for ABR to be a successful mass market implementation. My next post will show what alternatives exist to ABR in mobile networks for efficient video delivery.
No comments:
Post a Comment