Can not generating thumbnails with publish stream used video codec VP8

In *[install-dir]/conf/VHost.xml file, I Put

com.wowza.wms.transcoder.thumbnailer.HTTPProviderGenerateThumbnail
thumbnail

none

And when I published stream with video codec H.264, I can get thumbnail via this link
http://[my ip]:8086/thumbnail?application=live&streamname=sss&size=640x640&fitmode=letterbox&format=png

But when published stream with video codec VP8, I cannot get the thumbnail.

Please help me to check about this. Why VP8 can not get thumbnail.

Thanks

As you see in the name of the module, this is transcoding functionality.
So you need to transcode the WebRTC codec in something that can be read by the module.

If you transcode your WebRTC stream to h264 it will/should work.

I am having issue capturing thumbnails for non transcoded, video codec h264. I am following steps mentioned in https://www.wowza.com/docs/how-to-generate-thumbnail-images-of-live-streams. The transcoded stream from mpeg4 to h264 works for capturing thumbnails.
Any response would greatly appreciated!

Read transcoded stream with ffmpeg and compare with non transcoded stream to see what are the differences in the codec properties.