How about select the autotimeshift function?

1)please make sure the usb device is connect
2)goto STB Setting Menu->autotimeshift menu. you can select 30min,60min,90min,120min.
3)exit all menu and you can press (info key+8) to open the record info
4)then you can press OK Key to replay current channel

PVR Previous key: start play channel from zero time 
PVR next key:     start play channel from current time
PVR forward key: forward the current channel
PVR backward key:backward the current channel