1. A method of determining TV channel information, the method comprising: at a digital video conversion device having one or more processors, radio-frequency circuitry and memory for storing program modules to be executed by the one or more processors, wherein the digital video conversion device is communicatively coupled to a TV set and a TV signal source, respectively, so as to pass TV signals from the TV signal source to the TV set: receiving a TV channel identification request from a mobile terminal via a wireless communication channel; in response to the TV channel identification request: acquiring an image from the TV signals currently broadcasted on the TV set; extracting a plurality of station logo characteristic sets from the image, wherein each station logo characteristic set corresponds to one of a plurality of station logo templates, wherein each station logo template includes a respective station logo type and logo position information for a respective station logo image region, and wherein extracting the plurality of station logo characteristic set for a corresponding station logo template in the plurality of station logo templates includes: in accordance with a determination that the respective station logo type in the corresponding station logo template is a static opaque station logo type, generating a normalized block-level color histogram for a station logo image region in the image; and in accordance with a determination that the respective station logo type in the corresponding station logo template is a static semi-transparent station logo type, generating a perpetual hash value of the station logo image region in the image; calculating a similarity score between each station logo characteristic set and the corresponding station logo template of said each station logo characteristic set; identifying one of the plurality of station logo templates as matching the image based on their similarity scores; and returning TV channel information associated with the identified station logo template to the mobile terminal.