Market research as well as experience with customer deployments globally show that personal cloud and mobile video use is on the rise. As part of this, more people prefer to stream content than download it. This is somewhat akin to the difference between renting and owning content, the former is less expensive and comes with the expectation that video can be watched instantly instead of waiting for a potentially long download. On the other hand, if you need offline use, streaming won't cut it.

This begs the question of whether progressive downloading or streaming is better for personal cloud video. I do not pretend to be a CTO, nor did I stay in a Holiday Inn last night, but here are my thoughts.

In one corner, progressive downloading, sometimes called http streaming, transfers a video file from a cloud to an app/client on a smartphone, tablet, personal computer, browser or other endpoint. Contrary to popular belief, however, depending on the network bandwidth and video encoding, the video may start playing as soon as enough of the file has downloaded. This myth buster says that with progressive downloading, you don't need to wait for the whole file to download to start watching.

In the other corner, video streaming, popularized by video services such as Netflix, exchanges commands over a network to control playback of video, such as start, stop, skip, advance, rewind, etc.

There are many detailed articles that compare progressive downloading vs. streaming for video, and you can google this for more. The general consensus is that neither is optimal for every situation. For example, if you expect that users will have fast connectivity, streaming is better, but if users do not, progressive downloading is superior because it can deal with buffering that makes streaming over slow connections insufferable. Remember that the next time you stream a movie, tv show or video clip and the video is choppy or interrupted. I don't know about you, but to me, this is still the norm, and I live in Silicon Valley, the land of fast networks and 4G mobile data.

The approaches involve other considerations. Progressive downloading may result in more bandwidth consumed, because unless the user stops a downloaded, the entire file downloads, whereas with streaming, if the user stops watching, only a portion transfers. On the other hand, if a video is watched more than once, progressive downloading uses less bandwidth, because once downloaded, it does not generate more traffic.

When it comes to protecting content such as copyrighted material, streaming is superior because the video is discarded after playing, while with progressive downloading, video remains on the client until deleted. There is also the critical issue of cost. Adding a bank of streaming servers or a content delivery network with network caching is non-trivial in terms of capital outlay and/or operating costs. Then there is the question of high definition, which places more strain on a network when streamed, so in this case, progressive downloading may be wiser.

So which is ultimately better for personal clouds? The answer as usual, is both, neither, or it depends :) Different personal cloud services have different audiences, purposes and policies regarding commercial video storage. For example, iTunes, integrated with iCloud, supports both - content can be downloaded or streamed. As noted, the trend is streaming, as more users have good enough connectivity. This is fine for markets where people can afford that, but in many parts of the world, that is not yet the case. In those places, progressive downloading not only makes sense but is the only technique that is feasible.

For any personal cloud service, it boils down to key questions such as, are users allowed and encouraged to store commercial video in their cloud or is the personal cloud primarily for user generated video such that streaming is an unnecessary luxury? Do most projected users have fast bandwidth such that streaming will offer a good experience? Do the economics of the service warrant the additional cost of streaming? How much do users expect high definition?

Our experience in working with large personal cloud providers worldwide shows that for today, progressive downloading is a more universal approach that results in a better experience and has a better bang for the buck. The extra cost of streaming is not appreciated by many users. That said, there are certainly markets where video streaming makes sense and is required. At some point soon, the scale will most likely tip towards streaming, but we're not quite there yet. What's important is that the technology underlying your personal cloud service is flexible to support both approaches as appropriate.