Issue related to VideoWriter in Andorid

Android/Java
1

Hi there. I’m newcomer to opencv. I have a face dection program it detects face from frames of a MP4 video and then using VideoWriter to export frames into a MP4 video, it works fine in Linux but not in Andorid. I hope some could answer my following issues:

  1. A outdated link says I can’t load arbitary video in Andorid. Is it still true now? Do I still need convert MP4 video to AVI video ?
  2. I have tried using MJPEG-based AVI video. A pretty weird behavior of VideoWriter is that file name of exported video must contain digit character, code snippet copied from opencv/modules/videoio/src/cap_images.cpp
    CV_Assert(_filename);
    filename_pattern = icvExtractPattern(_filename, &offset);
    CV_Assert(!filename_pattern.empty());

and inside of icvExtractPattern function:

while (pos < len && !isdigit(filename[pos])) pos++;

So the truth is changing file name from output.avi to outputt_1.avi. Everything runs as I expected Why ?