Looks like I’m a little late to the party, but I’m catching up with some great posts at omino.com. I’ve always admired David Van Brink’s qt_tools project, A great open source command-line set of tools for dealing with Quicktime, and it looks like he’s now sharing more quick hits of his pixel, motion and scripting explorations. Very fun David.
Last time, we talked about using a Socket Object in After Effects CS3 to parse a data feed with E4X XML parsing. There are a lot of useful workflow operations I can think of that could make use of data feeds, but After Effects is a visual medium, so let’s do something visual, let’s import a set of flickr photos matching a tag. This is a proof of concept script, and before you plunge into experimenting you should check the terms of service of the web feed provider and respect the use of images you download. That said, let’s take a look at some code.
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I had an email conversation with Matt, who wanted to fetch some xml to play with the new E4X XML parsing in AE CS3. We’re still waiting for the ExtendScript HttpConnection Object to show up in After Effects, but we do have access to the Socket Object. The Socket Object is a little low level, but if you are using web feeds and don’t need authentication it’s actually pretty easy.
This code segment outlines the basics.
webConnect = new Socket;
response = new String;
if(webConnect.open("feeds.feedburner.com:80","UTF-8")) {
webConnect.write('GET /current/currentpicks?format=xml HTTP/1.0nn');
response = webConnect.read(100000);
response = response.toString();
var xmlStart = response.indexOf("<?xml");
var xmlString = response.substring(xmlStart, response.length);
alert(xmlString)
webConnect.close();
} else {
alert (""unable to open webConnect via Socket"")
}
We open a Socket and connect to, in this case, a feedburner feed. We use the read() method to read in the XML, and since the Socket object includes the header we use indexOf to find the beginning of the XML and substring to read to the end of the line.
A couple of gotchas in the code. In this case the header tells us the document encoding is utf-8 so we explicity set it with
webConnect.open("feeds.feedburner.com:80","UTF-8")Also, when Matt and I were initially exploring this we were just getting the header. It looks like a GET request with
response = webConnect.read()
allows a block response, and the later content was going off into the ether, If we used
response = webConnect.read(100000);
with a sufficiently large number to include all of the XML we got all of the contents of the XML file. This seems like a really bad idea, since we’ll never know the size of the XML file unless we munge some headers and setting it arbitrarily high also seems like a bad idea. Can someone who’s spent more time with the Socket object leave a comment or email me on how to handle the block response or alternatives to setting a big count for the read() method? I’d appreciate it.
Anyway, that’s the basic idea. You’d then parse the xmlString variable and do fun stuff with it. One heads up, the sample above includes namespaces, so be sure to read the section on namespaces in the Scripting Guide.