http://elearningcurve.blogspot.com/2008/06/online-presentation-tools-as-kn
After yesterday's short digression into some of the finer points of heuristic evaluation, today I'm returning to the matter at hand: an assessment of the features and functionality provided by the authorSTREAM and SlideShare hosted presentation distribution services.
Now read on...
authorSTREAM is a web-based PowerPoint presentation sharing platform from authorGEN Technologies. After creating a presentation in Microsoft 
PowerPoint, content creators can upload presentations to the authorSTREAM website. During the upload process the content is converted Adobe to Flash SWF format displayed via the Flash player. Content creators can use the provided HTML code to embed the presentation in a blog or website, as well to share the presentation via e-mail, and submit the content to YouTube. authorSTREAM also enables users to share their presentations via mobile devices that support MV4 playback such as the Apple iPod or iPhone.
Slideshare supports a range of import file types, including PowerPoint PPT, OpenOffice.org Impress, and PDF format. Broadly speaking, we can say that the SlideShare upload process shares many characteristics 
with other Web 2.0 tools, and is in fact very similar to the authorSTREAM submission procedure. Generally speaking, once a file is uploaded and converted to SWF, it is publicly available.
The content creators can choose to make the slide show available to be downloaded. Interestingly for a service provided by a for-profit organization Slideshare is linked with Creative Commons, so various attribution licenses are supported (click here for more thoughts on Open Source Software). As with other hosted Web 2.0 services (including YouTube), a presentation can be viewed in the small screen or take the full screen of a monitor.
Table 1 authorSTREAM & SlideShare Feature Comparison
| Feature | authorSTREAM | SlideShare |
| PowerPoint animations | Yes | No |
| PowerPoint animations with audio | Yes | No |
| Motion-based content (i.e. Flash animation / movies) in slides | Yes | No |
| Rehearsed timings | Yes | No |
| Voice-over narration | Yes | No |
| Embed code | Yes | Yes |
| Statistics | No | Yes |
| RSS Feed support | Yes | Yes |
| Full-screen playback | Yes | Via SlideShare.net only |
| Private content | Yes | Yes |
| PowerPoint file download | Yes | Yes |
| User Groups | No | Yes |
General Observations: Content Authoring
authorGEN provide authorPOINT Lite, an advanced multimedia presentation creation software utility, which installs in PowerPoint and offers a host of features for power users. Presenters can upload presentations directly from within PowerPoint with this add-on software.
authorPOINT is an advanced multimedia presentation creation software, which installs in PowerPoint as an add-in and provides a range of features for power users. Presenters can upload presentations directly from within PowerPoint with this utility. SlideShare does not offer any offline desktop utility to support the website service.
General Observations: Audio
authorSTREAM handles voice-over audio in presentations very well. Audio is retained in narrated PowerPoint presentations when uploaded to authorSTREAM. Authors can also create audio presentations using either live or pre-recorded audio as a media type via authorPOINT, before uploading to authorSTREAM.
SlideShare on the other hand, has a “slidecast” feature where the content author synchronizes a pre-recorded audio file online following upload to the server.
authorSTREAM's offline desktop application is a very flexible feature - potentially very useful for e-learning content, in my view.
General Observations: Content Distribution
One very usable feature of SlideShare is it facility to enable extended distribution of content outside of it's native hosting environment. 
By clicking on the <embed> button on the UI, both an author and any other user can either share the presentation via any one of a range of social networking services (see the screenshot for some examples) as well as provide the source code to enable the presentation to be embedded in a blog or web page, very similar to YouTube's functionality. A case could definitely be made that this type of portability will support the creation of Internet memes in environments where YouTube is not appropriate (due to bandwidth issues, for example).
Conclusions
So which service is better? Well, I guess that comes down to WIIFM - what's in it for me. The broad sweep of features and functionality are pretty similar on both services: deficiencies in one are accommodated by lack of functionality in the other, so it really comes down to personal choice.
My user experience of authorSTREAM was slightly superior to that of SlideShare: upload and conversion times were lower on the former service, for example. Equally, the enhanced slide animation and transition support on authorSTREAM was a positive advantage, as was the ability to view presentations in full-screen mode via a third party environment (my blog in this case). I also prefer the extended functionality afforded by the desktop-based client client, as well as the better audio integration.
In the end... well, I recommend that you try both out yourself, and you decide which service meets your needs.
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