Cloud Computing?

Why consider the "cloud"?

The biggest advantage of cloud computing is that it provides us a bunch of services and resources that are accessible with minimal configuration. In this blog post, I will show you how to implement a Media Engine that uses a cloud based video software solution, Zencoder, to generate movie previews.

About Zencoder

Zencoder is cloud-based video and audio encoding software as a service (SaaS). It is hosted on Amazon Web Services. Zencoder provides many, many encoding features, but for this post we'll stick to the basics, i.e. creating a preview and some thumbnails of a movie file.

Advantages

Writing a cloud based Media Engine

First thing I did, was signup for a Test license on the Zencoder website. You'll receive an API key which is passed with each Zencoder request.

Next up is choosing your way of communicating with the Zencoder API. This API is REST based, so it's possible to only use plain old HTTP GET/POST/PUT requests and some JSON. However, there are already a couple of managed code libraries available which make it even simpler to send our encoding requests. In this post, I've used the excellent open source (MIT license) C# Zencoder library of Chad Burggraf.

Setup

Before going further with the actual implementation, let's discuss how Zencoder processes video encoding requests.

When you want to encode a video, evidently it needs to be accessible to Zencoder. Therefore we need to put in on a place where Zencoder can upload and process it. There are four options available:

1. HTTP/HTTPS
2. FTP/SFTP
3. Amazon S3
4. Rackspace Cloud Files

For this demo, let's simply put the movie files into the public folder of a dropbox account. This folder can be accessed by anyone through an HTTP address (e.g. http://dl.dropbox.com/u/<account_number>/plane.avi). Needless to say, this is NOT the way to go for production processes :-)

Afterwards, we will download the generated outputs ourselves from the Zencoder storage.

Implementation

So let's look at the implementation now. Once you've made your movie available through any of the described options, you're ready to send the encoding request to Zencoder.

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Zencoder zencoder = new Zencoder("your-api-key-goes-here");
CreateJobResponse response = zencoder.CreateJob(action.Path,
    new[]
    {
        new Output
        {
            Label = "converted",
            FileName = Guid.NewGuid()+".mp4", // output file name
            Thumbnails = new []{new Thumbnails{ Label = "Thumbs", Number = 3}}, // generated 3 thumbnails
   // Note: check zencoder documentation for many more encoding options.
        }
    });

Notice the response object we get on line 2. This will tell us if the encoding job was correctly created and provides us with the details of the created job (e.g. job id). Since the Zencoder API is completely asynchronous, you'll need this information to get the progress status of your job.

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JobProgressResponse progress = zencoder.JobProgress(response.Outputs.First().Id);
while (progress.State != OutputState.Finished)
{
...
}

Once the job has completed we can get the location of the generated files and download them.

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Job details = zencoder.JobDetails(response.Id).Job;
using (WebClient webClient = new WebClient())
{
 // download the movie preview
 Uri url = new Uri(details.OutputMediaFiles.First().Url);
 string previewFileName = App.GetTemporaryFile("mp4");
 webClient.DownloadFile(url, previewFileName);
 action.MoviePreviews.Add(new MoviePreview(previewFileName));

 // download the image previews
 foreach (Thumbnail thumbnail in details.Thumbnails)
 {
  url = new Uri(thumbnail.Url);
  previewFileName = App.GetTemporaryFile("png");
  webClient.DownloadFile(url, previewFileName);
  action.ImagePreviews.Add(new Preview(previewFileName, -1));
 }
}

Conclusion

I hope this post has given you a small taster on how you can easily benefit from cloud services within ADAM. I've added a simple sample media engine that uses Zencoder to this post. To play with it, just create a free test account at Zencoder and put in your API key.