CatCam

At Make Tech Easier, Damien shows how to set up a motion sensing webcam on Linux, and suggests storing the files on Dropbox to view from anywhere. Great idea!

This repo simply makes use of the Dropbox API to list the Dropbox files with file sizes.

Why use the API and not just the Dropbox web site, you ask? Well, because Dropbox doesn't list how big the files are (at least not in 2017), giving no indication of which files have significant content ..not without clicking each file's properties, which, umm.. no.

Prereqs

• A Dropbox account
• A Linux box with a webcam (somewhere near your cats) 😸 😸
• A web site to publish these PHP files

Set up

1. To use the Dropbox API, go to https://dropbox.com/developers/apps to create an app and get a token. To protect my other Dropbox data, I chose to use the kind of app that's restricted to a single folder.

2. After downloading or cloning this repo, use the config template to create a config/catcfg.inc file with the Dropbox app name and token. For example:

   $c = Array(
     'app' => 'myunique_dropbox_catcam',
     'tok' => '56YrsSSSSSSome-Long-64-Character-Token-For-Your-DropboxAPP_BBBgh',
   );

3. Setup and run motion to capture the videos. I have a cheap webcam on a Linux box that runs the motion application. When it senses motion (a field of a few hundred pixels has changed), it writes a movie file to the same folder that is owned by the Dropbox app. See Damien's article for information on setting up the Motion application. The following diff shows the only changes I made to Motion's configuration file, based on where my camera was placed and the approximate size of a cat on the far wall on my home.

   

4. Upload this catcam folder to your web site.

   Note: If you're site doesn't run Apache or allow .htaccess file overrides, hide your catcfg.inc file some other way, such as moving it out of the web folder to another location on your server. Update the include statements in the PHP scripts accordingly.

5. Point your browser to the /catcam/ folder on your web site and click away!

Programming notes

So, when first run, the token is obtained and an API call made to /list_folder, which returns an array of file entry records, with name, size, and other things. I only care about the name and size. Those are listed.

The /list_folder call will also return a has_more value of true and cursor value if there are more files than could be retrieved in this first call. These values are used to retrieve subsequent pages of results. So, if there are more pages, a button is shown with the cursor value below the list. At the time of this writing, looks like the default number of items per page is 2000. Could specify an item limit per page in the data passed to /list_folder, but nah.

When the user clicks the button, this same page is loaded but with the cursor as a POST parameter. That logic is at the top of the page, so that if a cursor is passed to this page, it'll call the /list_folder/continue API (with the cursor value) instead of the /list_folder one. Dropbox then retrieves the subsequent page of results.

For more info, see the Dropbox API doc on /list_folder.

I discovered that you can't share a folder that is used by a folder-restricted app. So, I added the download link to bypass the need to have account access to get the video. The link POSTs path and size info to Drobox's /download endpoint. I couldn't get PHP's file_get_contents() to work with the binary data stream, so I ended up using curl in the catget.php file.

And that's about it.