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I want to play 2 video files using a GStreamer pipeline on my screen. The first video is without an embedded alpha channel and I want the second video with an embedded alpha channel to be overlaid over the first one.

The alpha plugin seems to be for adding an alpha channel to a video stream initially lacking it, but it's not what I want. How do I compose videos with embedded alpha channels in gstreamer?

Here are 2 samples: betina.flv (A420 color format) and betina.mov (BGRA color format).

My task is not to create such files but to overlay them on top of plain non-alpha movies.

nponeccop
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  • So you want to do something like this? http://jakearchibald.com/scratch/alphavid/ but with `gstreamer`? – justbrowsing Sep 08 '13 at 00:39
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    And over another video as opposed to a static background image. BTW the `.ogv` file there seems to have an alpha channel embedded so if it turns out to be true the part of my question about video samples is answered. – nponeccop Sep 08 '13 at 09:17

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You will want to use videomixer, I just added auto conversion support with respect to alpha channels, it is in git master but not yet released.

Mathieu_Du
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    can you please elaborate on why should the QA choose that software over another? what are its key features? also, please be clear if you used it before and if you had a positive experience. – Lorenzo Von Matterhorn Sep 14 '13 at 18:36
  • OP asked a question about gstreamer, not sure I need to market it to him. – Mathieu_Du Sep 15 '13 at 14:29
  • its not about marketing. check here: http://meta.superuser.com/questions/5329/how-do-i-recommend-software-in-my-answers – Lorenzo Von Matterhorn Sep 15 '13 at 14:46
  • I'm not recommending software, I'm explaining how to achieve his goal with the software he already uses. – Mathieu_Du Sep 15 '13 at 15:15
  • @LorenzoVonMatterhorn: I explicitly stated in my question that I'm only interested in gstreamer-based solutions, so no software recommendations is taking place. MathieuDu: your pipeline generates a Y444 movie without an alpha channel so it's not helpful. I added examples of movies with embedded alpha to my question. – nponeccop Sep 15 '13 at 19:15
  • @LorenzoVonMatterhorn I think your confusion is from not knowing what `videomixer` is. This answer is not "*use my software instead*", it is "*use this plugin hosted on the official site of the software you are currently using that I contributed to*" – Scott Chamberlain Sep 15 '13 at 20:45
  • @ScottChamberlain yes, i realized after a while he was simply referring to the plugins and respective command-line executables to use them and not really to additional software, thank you for bothering to comment tho. – Lorenzo Von Matterhorn Sep 15 '13 at 21:55
  • @nponeccop , you will want to use avdec_vp6a as the encoder then, don't hesitate to drop by #gstreamer on freenode :) – Mathieu_Du Sep 16 '13 at 04:17
  • Actually, disregard my last comment, there's no encoder for vp6a in the gstreamer plugins. You should really come on the IRC to discuss a solution :) – Mathieu_Du Sep 16 '13 at 04:24
  • I managed to find a solution myself. I don't need to encode video with alpha. I need to use `gstreamer` to merge 2 sources I already have: a source with alpha and a soure without alpha, and get a source without alpha as a result. So a plain mixing of `betina.mov`/`.flv` with another video using `videomixer` worked. I only needed to play with commandline a lot to find out the right combination and get a deeper understanding of `gstreamer` pipelines and color formats. – nponeccop Sep 16 '13 at 09:29
  • Yeah of course, I thought you really wanted alpha in your files but OK, if everything works now that's perfect :) – Mathieu_Du Sep 16 '13 at 14:00
  • So yeah you ended up using videomixer, you should accept my answer I gues ;) – Mathieu_Du Sep 16 '13 at 14:01