Playing a video from DeDup 1.5.3's scanner on Android

The Play button on a video in DeDup 1.5.3's video scanner hands the file to another app on your phone. The Play button doesn't use a player inside DeDup. If Android refuses to open the file, or no app can play it, you get a short message instead.

What happens when you tap Play

1. DeDup picks an address for the video (see below).
2. It builds a request to view the file as a video and asks Android to show a chooser titled "Play Video".
3. You pick an app, and that app plays the video.

Tapping elsewhere on the video tile selects it for deletion rather than playing it.

How access is resolved

DeDup chooses between two kinds of address:

• A link from DeDup's own file provider. This is used when the video has a known file path, a file exists at that path, and the provider can describe it. The code's stated reason is that this link lets the other app read the video without depending on DeDup's own permission to your media. DeDup's provider is set up to cover external storage, DeDup's app folder and the device root.
• The media library address. This is the fallback when the path is unknown, the file isn't found at that path, or the file is outside the provider's folders. It's the address that Android can refuse if DeDup has lost read access to the video.

In both cases the request carries the read-permission flag, which asks Android to let the app you pick read that address.

When it fails

DeDup launches the chooser through a small wrapper. According to the code's comments, Android checks at launch that DeDup is allowed to pass the address on. If it isn't, Android throws a security error. The comments list when this can happen: if media access was revoked or limited, if the scan result is old, or if another app owns the file. The wrapper catches that error. It also catches the case where no app can handle the request.

Either way you see a short message on screen: "Can't open this video. It may have been moved or deleted, or DeDup no longer has access to it." The two failures show the same message. DeDup doesn't tell you which one happened.

The message only covers a failure at launch. Once a player app opens, DeDup can't see what happens next. If that app can't load the file, any error comes from that app.

Scope of this post

Checked against: DeDup 1.5.3 source code (Android).

Not tested on a device: which apps appear in the chooser, how any player behaves, whether the message appears on a particular phone, or how Android treats the grant on different versions. The explanation of why the security error occurs comes from comments in the code, not from running it.