Design of core subsystem of TI digital set-top box

A digital set-top box (STB) is connected to the TV and an external source to convert the signal into content that can be displayed on the TV screen. After adding a hard disk drive (HDD), the set-top box solution can also support PVR (Personal Video Recorder) functions. This article will detail STB's core subsystem design.

Design considerations

A digital set-top box (STB) is connected to the TV and an external source to convert the signal into content that can be displayed on the TV screen. After adding a hard disk drive (HDD), the set-top box solution can also support PVR (Personal Video Recorder) functions. A common stand-alone component called TIVo is an example of PVR. Like many home electronic terminal devices, remote control is an important component of a complete system. Many consumer products have begun to use RF remote control with the help of the RF4CE solution that TI is leading. These devices depend on the remote control and the low-power RF chip and microprocessor on the STB.

Generally, digital STB (PVR) can be divided into several main components; digital media processor, audio decoding and processing, video decoding and processing, tuner, audio and video output, IrDA or LPW remote control, various interfaces and power supply. TI's product line has introduced many integrated circuits that can achieve the expected performance levels. It is essential to take full advantage of high-performance audio-video codecs, graphics acceleration, communications, and support for integrated applications used in the home entertainment experience.

Block diagram of the core subsystem of TI digital set-top box

The kernel subsystem includes:

Digital Media Processor – TI ’s digital media processor can handle decoding, transcoding / encoding (converting from one format to another format), and conversion of various media streams (adjusting higher bit rates to lower Bit rate) and other complex processing functions, in addition to meeting system-level functions such as decryption, encryption, packetization, and media stream transmission. In addition to broadcast content, TI-based set-top boxes can seamlessly support content from home networks or directly from the Internet. TI's fully programmable devices enable fast compatibility with new codec technologies (used by all Internet sites or PCs), including future versions that were not foreseen at the time of product design. TI's media processor series is software compatible, which means that software investment can be reused in various products from SD boxes to HD boxes to other products, thereby reducing development time and costs.

RF demodulation-COFDM / QAM / QPSK / ATSC demodulation, forward error correction (FEC) and video demultiplexing.

The MSP430 microprocessor in the MCU-STB is very versatile. It can be applied in all ranges from managing the interface connected to the remote control to managing the power consumption of the STB component through the control and application of multiple different operating modes. MSP430 can extend the battery life of the remote control. No matter which working mode is used, it can significantly reduce the power consumption of the STB, while almost not increasing the complexity of the system.

Video Interface-Select the video source decoded / encoded by ADC / DAC and DSP. Both the video front end and the output stage require high-performance operational amplifiers to amplify the video signal. For this terminal device, it is essential to support multiple ATSC DTV formats, NTSC / PAL, composite video, and S-video. Once HDTV becomes the mainstream standard, products that support 1080p Full HD resolution with 3D adaptive filtering will be everywhere.

Audio interface-allows audio to be digitized by the audio converter and processed by the DSP to provide high-quality audio to meet the needs of MPEG / AC3. The audio is also converted back to analog format and then played through stereo headphones via stereo output jacks. With high SNR (signal-to-noise ratio) and analog low-pass filtering, high-quality audio output is guaranteed.

User interface-allows users to control video / audio I / O sources while communicating with the system network. The user interface also includes a connection to the remote control via IrDA or a low-power wireless device that resides on the component itself and the remote control component.

Broadband and wireless connections-Allow interactive TV, games, streaming audio and video, Voice over IP (VoIP) and video telephony to send and receive via ADSL, cable modem and 802.11 interfaces.

Power conversion – Contains AC to DC conversion to create the main power for the component itself. Almost all functional blocks in the STB require a special power solution; core and I / O power for the main processor, DDR memory, and tuner Power supply and video / analog signal chain. However, in this era of energy protection, the government is constantly promulgating new policies on standby power consumption and consumer product efficiency and strengthening the implementation of existing plans. Almost all current plans to regulate STBs are voluntary, but the implementation of mandatory requirements is imminent.

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