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VCD 机工作时,光盘在主轴电机带动下做恒线速度转动,激光头发出激光束投射到光盘坑点轨迹(信息轨迹)上,光盘又将激光反射到激光头,激光头内部的光电转换器将反射回来的光还原成电信号。激光头送出的电信号送到 RF 前置放大电路,在 RF 放大电路中进行放大,形成 RF 信号(即光盘上的视频数字信号和音频信号),再送至数字信号处理(DSP)电路。DSP 电路也将 CD 格式编码的光盘压缩音视频数据信号(称为位流)解调还原成记录前的压缩数据,或将 CD 光盘的音频数据解调还原成16位数字音频信号,再送到解码电路。其中声音信号经声音数据解压电路解压缩处理后,送到音频数/模转换电路,将数字音频信号转换成模拟音频信号去音频输出插孔。图像信号经图像数
VCD machine work, the CD-ROM drive in the spindle motor to do a constant speed of rotation, the laser hair laser beam projected onto the trajectory of the CD pit (information track), the laser and the optical disc to the laser head, the laser head photoelectric converter Will reflect the light back into electrical signals. The electrical signals sent by the laser head are sent to the RF preamplifier circuit and amplified in the RF amplifier circuit to form an RF signal (ie, a digital video signal and an audio signal on the optical disk) which is then sent to a digital signal processing (DSP) circuit. The DSP circuit also demodulates the CD-compressed audio and video data signal (referred to as bit stream) encoded in the CD format to the compressed data before recording or demodulates the audio data of the CD disc into a 16-bit digital audio signal and sends it to the decoder Circuit. The voice signal is decompressed by the voice data decompression circuit and sent to the audio digital-analog conversion circuit to convert the digital audio signal into an analog audio signal to the audio output jack. Image signal by the number of images