Use the file command to find out whether it is a gz or ar package.
# ls kino2_0.21_arm.ipk
kino2_0.21_arm.ipk
# file kino2_0.21_arm.ipk
kino2_0.21_arm.ipk: gzip compressed data, was "kino2_0.21_arm.ipk", from Unix, max compression
# mkdir kino2
# cd kino2/
# tar zxvf ../kino2_0.21_arm.ipk
./debian-binary
./data.tar.gz
./control.tar.gz
# tar zxvf data.tar.gz
./
./opt/
./opt/QtPalmtop/
./opt/QtPalmtop/bin/
./opt/QtPalmtop/bin/kino2
./opt/QtPalmtop/apps/
./opt/QtPalmtop/apps/Multimedia/
./opt/QtPalmtop/apps/Multimedia/kino2.desktop
./opt/QtPalmtop/i18n/
./opt/QtPalmtop/i18n/ru/
./opt/QtPalmtop/i18n/ru/kino2.qm
./opt/QtPalmtop/pics144/
./opt/QtPalmtop/pics144/kino2/
./opt/QtPalmtop/pics144/kino2/tv.png
./usr/
./usr/local/
./usr/local/bin/
./usr/local/bin/mplayer
./usr/local/etc/
./usr/local/etc/mplayer/
./usr/local/etc/mplayer/codecs.conf
./usr/local/lib/
./usr/local/lib/mplayer/
./usr/local/lib/mplayer/vidix/
./usr/local/lib/mplayer/vidix/w100_vid.so
#