code: private void decodeVideoHeader() throws IOException {
          int length = file.readInt();
          file.skipBytes(4);//video frame count is always zero with ffmpeg encoded files...
          videoWidth = file.readUnsignedShort();
          videoHeight = file.readUnsignedShort();
          byte[] videoEncodingBytes = new byte[4];
          file.readFully(videoEncodingBytes);
          videoEncoding = SmjpegVideoEncoding.fromMagic(videoEncodingBytes);
          file.skipBytes(Math.max(0, length - 4 - 4 - 2 - 2));
      }
docs: /*
  Optional video header:
  4 bytes magic - "_VID"
  Uint32 video header length
  Uint32 number of frames
  Uint16 width
  Uint16 height
  4 bytes video encoding  ("JFIF" = jpeg)