As Calibre includes its own Content Server, one question that many users ask is why should they use calibre2opds catalogs rather than simply sticking with the Calibre Content server? This is a comparison of the two approaches:
Calibre’s content server is active. You must install it, with all its dependencies, and then run it and maintain it. The hosting system must therefore be capable of running the full set of Calibre software. The Calibre library must be visible to the Content server, or probably copied to where it is running. The Calibre Content Server uses a significant amount of memory, which might be precious on the server (I often run on servers with 512 kb total ram). The Content Sever wants to talk HTTP over TCP, meaning that anything in front of it must act like a client. It doesn’t support SSL (authentication is visible) or password-per-user. However, it does give up-to-date answers, which is a very good thing. Searching for books meeting specific criteria can be done which is another good thing
Calibre2opds generates static HTML pages. In effect this generates a web site for downloading your books which means that you do not require Calibre to be running to use the catalogs. This gives you a much wider choice of where you can host the calibre2opds catalogs. For instance it can be hosted on web servers in environments that would not be capable of running the Calibre Content server. Calibre2opds can use facilities of the hosting environment such as SSL and its security features. As an example if using the apache web server calibre2opds can run as a virtual host and use the Apache security features to give finer grain security than the Calibre Content server can offer.
Calibre2opds does not have the search facilities of the Calibre Content Server (yet) but it makes up for this by having a hierarchically structured catalog which many find easier to use than the flat catalog structure of the Calibre Content Server. The user can configure many options of the catalog structure to get it optimised for their particular use. The OPDS standard is still evolving, and the OPDS catalogs can be optimised for specific devices that do not necessarily support the full OPDS standard. You have to rerun the calibre2opds generate process to make books newly added to your Calibre library visible as changes are not picked up dynamically, although you can configure your system to automatically run the generation regular intervals.
The following table shows key features of the two different approaches for delivering ebooks over networks.
|Feature||Calibre Content Server||calibre2opds|
|Multi-Platform||Windows, Linux, MacOS||Windows, Linux, MacOS|
|Run from USB stick||Yes||Yes|
|Calibre needs to be running||Yes (Content Server component)||No|
|Built-in Web server||Yes||No – uses external web server|
|Custom Column Support||Yes||No (on wish list)|
|Run under Web Server||No||Yes|
|Security||username/password||hosting environment security|
|SSL supported||No||Yes (if hosting environment supports it)|
|Structured catalogs||No||Authors, Series, Tags, Recent Books, Ratings (optional)|
|Multiple catalog levels||No||Yes|
|Customisable catalog sections||No||Yes|
|Split sections by letter||No||Yes|
|Suppress Download links (browse only)||No||Yes|
|Coverflow in HTML catalogs||No||Yes|
|Limit formats in OPDS catalogs||No||Yes|
|Limit formats in HTML catalogs||No||Yes|
|Profiles for catalog settings||No||Yes|