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I came here because when i export my render in AVI Raw (RGBA) i got some render issues. There is some kind of 1 pixel shift in some pixel row :

enter image description here You might need to zoom to see it

This problem doesn't appears in blender render preview and it's still there if i render in .jpg at first and create a video with the blender's video editor. Here is what i see in blender with my render setting :

enter image description here

Because it appears only when i export the video i think it come from the compression process but i don't have enough knowledge on it to find a solution by myself :/

Thank you

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  • $\begingroup$ Your trying to save unassociated rgba in a format, that doesn't support the alpha channel (AVI). Render it with a not transparent background: choose RGB, goto Properties > Render > Film and uncheck transparent. $\endgroup$
    – Leander
    May 24, 2018 at 7:57
  • $\begingroup$ That was that, thank's a lot ! any idea how to render with alpha channel and without this bug ? (tried a lot of solution but whether there's this bug whether the compression is too high and the quality of image is too low) $\endgroup$
    – MBP
    May 24, 2018 at 9:33
  • $\begingroup$ This is not a bug. You have to choose a format which supports alpha channels. There are not builtin video formats with alpha in Blender currently (such as Prores), so you have to choose an image format such as PNG, TIFF, EXR, DPX with RGBA selected. It will render to an image sequence. $\endgroup$
    – Leander
    May 24, 2018 at 9:35
  • $\begingroup$ I tried the FFmpeg video exportation which contains codec that support alpha channel but i got the same issue if i render it directly or if i go through a PNG render that i render with the video sequence editor. So i guess the solution is to export it in PNG and using another program to create the .AVI file or is there something that i missed ? $\endgroup$
    – MBP
    May 24, 2018 at 9:44
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    $\begingroup$ Do you want a black background? Or do you want a transparent file? If you want a transparent video file you have to compose it in another application from blenders image sequence. Elaborate which ffmpeg format in Blender supports an alpha channel, please. $\endgroup$
    – Leander
    May 24, 2018 at 9:45

1 Answer 1

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Leander : "Your trying to save unassociated rgba in a format, that doesn't support the alpha channel (AVI). Render it with a not transparent background: choose RGB, goto Properties > Render > Film and uncheck transparent."

"This is not a bug. You have to choose a format which supports alpha channels. There are not builtin video formats with alpha in Blender currently (such as Prores), so you have to choose an image format such as PNG, TIFF, EXR, DPX with RGBA selected. It will render to an image sequence."

So the bug where due to the use of transparency and the RGBA mode on a file format that don't support it.

If you have issues rendering with transparency, i tried to render with alpha using ffmpeg video with the codec HuffYUV, PNG, and video codec #1 which support RGBA but either the quality was too bad either it has the bug that i came for in the first place. It seems like Blender don't have any proper way to render with an alpha mask. i will edit this comment if i find a proper way to do it without using another soft, anyway i'll solve this subject because the main problem is solved.

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