vs-thumb should not rely on standard streams to communicate result image back

[Thomas Voß]

vs-thumb right now streams extracted data to stdout by default (see [1]). The approach is brittle in the sense that any component (e.g., gstreamer or gstreamer plugin) writing to stdout can easily break the thumbnail. We have zero control over stdout and should thus either:

  (1.) Rely on specifying an explicit temporary destination file or
  (2.) Open a dedicated communication pipe to communicate back the resulting thumbnail to the calling process.

Please also see [2.] for the respective product bug.

[1.] http://bazaar.launchpad.net/~unity-team/thumbnailer/trunk/view/head:/src/vs-thumb/thumbnailextractor.cpp#L371
[2.] https://bugs.launchpad.net/zhongshan/+bug/1554867

[Michi Henning (michihenning)]

Writing via a temp file is way more expensive. (The old thumbnailer did that.)

Dedicated pipe sounds like the way to go.

[Michi Henning (michihenning)]

BTW, the problem referenced in the bug report isn't caused by something writing to stdout. There error there is caused by a missing/broken codec, it seems.

[Michi Henning (michihenning)]

Not sure there is a bug there at all, actually. The media scanner indexes the file, and the thumbnailer can't make a thumbnail for it because there is no codec for the file. So, no thumbnail. That's expected and normal behavior.

[Michi Henning (michihenning)]

Thomas tells me that this reliably happens for any video taken on an M10 or Turbo. Looks like something in gstreamer is indeed writing to stdout. I'll change it to run the pipe via a different file descriptor.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Launchpad Janitor (janitor)]

This bug was fixed in the package thumbnailer - 2.4+16.04.20160321-0ubuntu1

---------------
thumbnailer (2.4+16.04.20160321-0ubuntu1) xenial; urgency=medium

  [ Michi Henning ]
  * vs-thumb now uses a separate pipe instead of writing to stdout (LP: #1556835).

  [ CI Train Bot ]
  * No-change rebuild.

 -- Michi Henning <email address hidden> Mon, 21 Mar 2016 02:12:07 +0000