webm with alpha channel rendered differently between browser and player

[CHIN SHOU]

I have a webm with alpha channel I played with vlc player, there is some obvious artifacts. But if I playback it with chrome by embedded in video tag, the artifacts was disappeared and the video alpha channel seems very smooth . Does any body know why chrome render the alpha channel webm differently from vlc player. As far as I checked vlc  player it also use libvpx as the decoder. Does the chrome apply some anti-aliasing image render differ from the vlc ?

Thanks in advance

[James Zern]

Hi,

On Fri, Jun 21, 2024 at 8:58 AM CHIN SHOU <chinsh...@gmail.com> wrote:

I have a webm with alpha channel I played with vlc player, there is some obvious artifacts. But if I playback it with chrome by embedded in video tag, the artifacts was disappeared and the video alpha channel seems very smooth . Does any body know why chrome render the alpha channel webm differently from vlc player. As far as I checked vlc  player it also use libvpx as the decoder. Does the chrome apply some anti-aliasing image render differ from the vlc ?

Do you have an example file and log from vlc you can share? It would be good to add what versions of vlc and libvpx you're using.

Chrome doesn't do anything special beyond decoding the 2 streams and copying them to a YUVA destination:
https://source.chromium.org/chromium/chromium/src/+/main:media/filters/vpx_video_decoder.cc;l=350;drc=8f68d172f1e37377f10af23f6a44e53953fe8170