Change permission Android system/lib to load native library data

Question

I make an app that installed in Android system, my app using native libraries, I try this code to load native libraries :

//Load Libffmpeg
                try {
                    if (new File("/data/data/"+ packageName +"/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so").exists()) {
                        System.load("/data/data/"+ packageName +"/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so");
                    }else if(new File("/system/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so").exists()){
                        System.load("/system/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so");
                    } else if(new File("/system/app/"+ packageName +"/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so").exists()){
                        System.load("/system/app/"+ packageName +"/lib/"+ "libffmpeg-linphone-" + ffmpegAbi+".so");
                    }else {
                        System.loadLibrary("ffmpeg-linphone-" + ffmpegAbi);
                    }
                } catch (Throwable e) {
                    Log.w("LinphoneCoreFactoryImpl", "Unable to load optional library lib" + "ffmpeg-linphone-" + ffmpegAbi);
                }

                //Load Main Library
                try {
                    if (new File("/data/data/"+ packageName +"/lib/"+ "linphone-" + abi+".so").exists()) {
                        System.load("/data/data/"+ packageName +"/lib/"+ "linphone-" + abi+".so");
                    }else if(new File("/system/lib/"+ "linphone-" + abi+".so").exists()){
                        System.load("/system/lib/"+ "linphone-" + abi+".so");
                    } else if(new File("/system/app/"+ packageName +"/lib/"+ "linphone-" + abi+".so").exists()){
                        System.load("/system/app/"+ packageName +"/lib/"+ "linphone-" + abi+".so");
                    }else {
                        System.loadLibrary("linphone-" + abi);
                    }
                    Log.i("LinphoneCoreFactoryImpl", "Loading done with " + abi);
                    libLoaded=true;
                    break;
                }catch(Throwable e) {
                    if (firstException == null) firstException=e;
                }

at first this error was appeared :

java.lang.RuntimeException: java.lang.UnsatisfiedLinkError: dlopen failed: couldn't map "/system/lib/liblinphone-armeabi-v7a.so" segment 2: Permission denied

after that I try to put this code :

try {
                    process = Runtime.getRuntime().exec("su");
                    dataOutputStream = new DataOutputStream(process.getOutputStream());
                    dataOutputStream.writeBytes("chmod 644 /system/lib/\n");
                    dataOutputStream.writeBytes("exit\n");
                    dataOutputStream.flush();
                    process.waitFor();
                } catch (Exception e) {

                } finally {
                    try {
                        if (dataOutputStream != null) {
                            dataOutputStream.close();
                        }
                        process.destroy();
                    } catch (Exception e) {
                    }
                }

but the same error appeared again, is that impossible to make system/lib accesible by android app in system or my code is wrong ?