VAAPI/QSV encode video with alpha channel

[Wu2019]

Hello,

I use VAAPI (ffmpeg+libva+media-driver) to encode a WebM video from a raw video with RGBA.

The final WebM video don't save alpha information (maybe means AlphaMode is closed).  I don't know whether it is the hardware that support encoding a alpha frame？Or maybe there are some limitations of the open source software library implementation? Did I miss anything crucial?

Many thanks in advance for your help
Wu

[RahulU_Intel]

Hi,

Thanks for posting in Intel forums. We are checking on this internally. We will get back to you soon.

Thanks and Regards

Rahul

[Mark_L_Intel1 · Accepted solution]

Hi Ximing,

Sorry for the late response.

The best place to ask this question is FFmpeg forum because this forum is to support Intel media toolkit like Media SDK and oneVPL.

I did a quick to the VAAPI driver support FFmpeg QSV plugin, here is the support table. As you can see it should support Alpha channel if your codec is VP9. But FFmpeg might mask out the alpha channel, so you might need to solve this problem first. You can use software codec to encode and make sure the alpha is not masked and switch to qsv. If you still got question, please go to FFmpeg forum to post.

Mark Liu

[Wu2019]

Hi Liu,

Thanks for your help!

I'm glad it's not because the hardware doesn't support it. And I will try to adjust my solution based on this.

This is very helpful to me. Thank you again for your reply！

Wu

[Mark_L_Intel1]

Yes, I can find the Alpha support at the media driver table but I can't find information in the Media SDK side. So I think FFmpeg QSV might help on this.

Mark