protected static int get7BitsInt(byte[] data, int offset) {
        int b0 = data[offset + 0] & 0x7F;
        int b1 = data[offset + 1] & 0x7F;
        int b2 = data[offset + 2] & 0x7F;
        int b3 = data[offset + 3] & 0x7F;
        return (b0 << 21) + (b1 << 14) + (b2 << 7) + (b3);
    }
AKA a Synchsafe integer.
4 bytes hold a 28 bit number. The highest
bit in each byte is always 0 and always ignored.
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-audiovideo-module/src/main/java/org/apache/tika/parser/mp3/ID3v2Frame.java