256 bit AES encryption in Android
Verbosity

String myString = getOutputFile();
File myFile = new File(myString);
FileInputStream inputStream = new FileInputStream(myFile);


FileInputStream can take String as argument. I'd do this instead:

FileInputStream inputStream = new FileInputStream(getOutputFile());


Whoa whoa whoa! We are reading from the output file? Did you make a mistake? I dunno, but by simply removing some lines I've suddenly exposed what could be a flaw!

Clarity

You're making a lot of objects and doing things with them. Try putting some blank space in between. It groups statements together and makes the code more logical.

void encrypt() throws IOException, NoSuchAlgorithmException, NoSuchPaddingException,
        InvalidKeyException {
    FileInputStream inputStream = new FileInputStream(getOutputFile());

    File encodedfile = new File(path,"filename" + ".mp4");
    FileOutputStream outputStream = new FileOutputStream(encodedfile);

    SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, sks);
    CipherOutputStream cos = new CipherOutputStream(outputStream, cipher);

    int b;
    byte[] d = new byte[8];
    while((b = inputStream.read(d)) != -1){
        cos.write(d, 0, b);
    }
    cos.flush();
    cos.close();
    inputStream.close();
}