If the TV is equipped with an HDMI interface, you can connect the HDMI interface on the set-top box with the HDMI interface on the TV to output digital audio and video signals to the TV, and the audio-visual effect is better. Because the signal transmitted by this interface has both video signal and audio signal, it can save the trouble of audio line.
Functional requirements of set-top box
It is necessary to support the media processing functions required for basic services and extended services.
For basic services, one or more of AVS video, MPEG-2, MPEG-4, MPEG-4 Part1H.264, SMTEVC-1can be selected as the video decoding standard; Audio decoding can adopt MPEG-2/4AAC, MPEG-2 audio, Dolby AC3/5. 1, MPEG- 1Layer2 and MP3, etc.
When the technology and business are mature, one or two standards will be determined as IPTV audio and video coding and decoding standards.
For extended services, image display formats such as CIF or QCIF and H.26 1 or G.723 video coding and decoding standards must be supported, and G.7 1 1 audio coding and decoding standards can also be adopted. The reason why the multi-choice method is adopted is mainly to consider the patent fees of various audio and video coding and decoding standards, and so on.
In addition, the set-top box should support graphic display modes with resolutions of 640×480, 720×576 and 352×288, and each pixel should support at least 16 bit color. Support to display the contents of multiple planes at the same time, and tile or overlay images can be used; Support the ability to display characters and Chinese characters, and the coding of Chinese characters should meet the requirements of GB 18030.