Safari projects use the H.264 video codec for video streaming. All participants in the Safari OpenTok session must support this codec. There is currently a bug in the Android Chrome browser that prevents the device from streaming H.264 video to other participants. The remote participants see a black window instead of the live video. The Android Chrome browser can successfully decode the H.264 video from other participants.
This Chromium issue is being tracked here. The fix has been merged into the Chrome 63 code base.
There is a second issue where participants on Android Chrome get the on screen error message "Video Format Not Supported". In this case audio works but there is no video, just the error message. H.264 video codec support was added to Android Chrome in version 57. At present H.264 video codec is limited to Qualcomm (Kitkat and later) and Samsung Exynos (Lollipop and later) chipsets. As there is no software H.264 encoder implementation, only the aforementioned chipsets are supported. For additional details see here.