1. Field of the Invention
The present general inventive concept relates to an apparatus and a method of automatically compensating a difference between audio signals of an analog broadcast and a digital broadcast in which a magnitude of output audio signals of a simulcast that depend on a difference between modulation degrees thereof.
2. Description of the Related Art
Digital broadcasting began in 1998, but analog broadcasting is still being used. Simulcast is used to concurrently broadcast the same contents over a digital broadcast channel and an analog broadcast channel. According to the simulcast, even though the digital broadcast is received, a user can still use an analog television set to view the contents of the analog broadcast. Accordingly, a digital broadcast receiver has been developed for concurrently receiving the analog broadcast and the digital broadcast. Therefore, the same contents are concurrently transmitted over the analog broadcast channel and the digital broadcast channel for the same station, and the user can use the digital broadcast receiver to tune to a predetermined channel and view the contents over the tuned channel.
In a conventional analog broadcast, an audio signal of the analog broadcast channel is modulated and broadcasted according to the National Television Standards Committee (NTSC) standard, the Phase Alternation by Line (PAL) standard, or the SEquential Couleur Avec Memoire (SECAM) standard. In the NTSC standard, the audio signal of the analog broadcast channel is generally FM-standard-modulated and transmitted at a bandwidth of ±25 kHz. In the PAL standard, the audio signal of the analog broadcast channel is standard-modulated and transmitted at a bandwidth of ±50 kHz. The digital broadcast receiver generates and outputs a modulation signal, which causes a magnitude (i.e., an output level) of the audio signal output to a speaker to vary according to a frequency of the modulation signal. If the audio signal of the analog broadcast channel is transmitted at a standard modulation degree and the digital broadcast receiver receives and modulates the audio signal of the analog broadcast channel, there is no difference between the audio signal output of the analog broadcast channel and a corresponding digital broadcast channel that broadcasts the same contents (i.e., for the same station).
A problem lies in the fact that the audio signal of the analog broadcast channel is output using a wide dynamic range of transmission decibels in order to improve a sound quality of a commercial advertisement and an audio output at each broadcast station. The audio signal of the analog broadcast channel is over-modulated for transmission at two to four times a modulation degree of a standard-modulated audio signal. A magnitude of a demodulated audio signal of the analog broadcast channel is determined depending on the modulation degree of a transmitted audio signal. Therefore, the magnitude of the output audio signal of the analog broadcast channel that is over-modulated varies greatly compared to when an audio signal having the same contents is standard-modulated and output over a corresponding digital broadcast channel. Accordingly, since the audio signal output varies between the digital broadcast channel and the corresponding analog broadcast channel, a user is required to control the magnitude of the audio signal (i.e., the output level) whenever the channel is changed which results in an inconvenience to the user.