Download original firmware from an URL: http://update.tvip.ru/stb/<model>/<os>/release/tvip_firmware.ota.zip
Here, model is mediacenter model, for ex. s410; os is OS type (android or linux-qt).

$ mkdir firmware

$ unzip -o -q tvip_firmware.ota.zip -d firmware

$ ls -l firmware/
total 8272
drwxr-xr-x   6 vovan  staff      204  7 фев 13:55 META-INF
-rw-r--r--   1 vovan  staff  3870617 29 фев  2008 boot.img
-rw-r--r--   1 vovan  staff   360464 29 фев  2008 bootloader.img
drwxr-xr-x  19 vovan  staff      646  7 фев 13:55 system

For Linux firmware, roofs is located in system folder.
/usr and /home in Linux-Qt firmware are SquashFS images.

If you need to add symlinks, you should edit the following file: META-INF/com/google/android/updater-script

Compress:

$ cd firmware
$ zip -r ../unsigned_tvip_firmware.ota.zip .
$ cd ..

To sign a package, you will need:

• Java Development Kit OpenJDK или Oracle JDK
• singapk.jar tool and platform keys sign_tools.tgz

Sign OTA:

$ java -jar signapk.jar -w key.x509.pem key.pk8 unsigned_tvip_firmware.ota.zip signed_tvip_firmware.ota.zip