This document provides an introduction to digital set-top boxes (STBs). It defines an STB as a device that connects to an external signal source and decodes the signal into content that can be displayed on a TV. STBs are categorized based on their source (cable, satellite, IP) and recording capabilities. The document outlines the various stakeholders in the STB business, including OEMs, chipset vendors, middleware providers, operators, and more. It provides a generic overview of STB software architecture and data flow, explaining how broadcast signals are received, decrypted, decoded, and output to displays. Common STB hardware components like tuners, memory, connectivity ports, and peripherals are also listed.
2. What is STB?
A digital set-top box is a device that connects to an
external signal source and decodes that signal into
content that can be presented on a display unit such as a
TV.
Initially the term “STB” was used to represent all such
devices, including digital media receivers, Windows
Media extenders, gaming consoles, etc too, but
gradually got limited to be used only for broadcast TV
content viewing devices.
STB’s are categorized in different ways:
Based on source: cable box, satellite box, IP box, etc.
Based on recording capability: zapper box, PVR/DVR box, etc.
Based on return channel: one-way (broadcast), two-way,
hybrid, etc.
3. STB Business - Stake holders
Usually, STB’s are designed and supplied by OEM’s to the operators, with many
stake-holders in the supply-chain:
OEM’s:
Pace, Cisco, Technicolor, Humax, etc.
Chipset/SoC vendors:
Broadcom, ST, MStar, etc.
CAS vendors:
Latens/Pace, NDS/Cisco, Nagra, etc.
Middleware/Application vendors:
Google, NDS/Cisco, Nagra, Zenterio, Cubiware, SeaChange, TiVo, etc.
OTT service vendors:
Netflix, Amazon, Plex, Roku, etc.
Third-party system integrators (optional):
Red Embedded, etc
Manufacturers:
Flextronics, Jabil, etc.
Headend vendors:
ARRIS, Cisco, Teleste, Tandberg, Ericsson, etc.
Operators:
DIRECTV, Comcast, TataSky, Hathway, etc.
Content aggregators/partners, VoD partners, billing systems, etc… and more!
5. Data flow (generic) - Broadcast with PVR
Frontend
Demux
Descrambler
Audio
Decoder
Video
Decoder
Graphics/
UI
Scaler
&
Mixer
DAC &
Amp
HDD /
Storage
HDD /
Storage
Tuner Demod
TV /
Display
out
Speaker
CAS /
smartcard
CC /
Teletext
SI / EPG /
Private Data
RF-
in
Media
input
SW-TS
TS PES
(enc)
PES
(clear)
A A A
V V
V
G
CW
ECM
EMM
6. Data flow Explained
Frontend (NIM)
The tuner is the input/source point for the data/media stream. It could be
a satellite/cable/terrestrial tuner to tune to signals coming in over the RF
input feeds.
The demodulator converts the modulated signal into baseband signal
(with error correction modules).
In IPTV case, this module would be replaced by IP/LAN/network module.
Demultiplexer
The demux module can filter out video/audio/data using PID, TID, mask,
etc.
Descrambler
This module descrambles encrypted signals into decrypted signals. The
diagram shows the more common case of PES-level descrambling, while
TS-level descrambling is also possible.
CAS / smartcard (shown in red)
The CAS system supplies the decryption keys to the descrambler module,
if the client STB is has the necessary subscription rights.
CAS can also control encryption & decryption in case of PVR recordings.
7. Data flow Explained (contd.)
Audio Decoder & Output
The audio PES is parsed, and the audio ES is passed to the audio bit
buffers. Then audio decoding and PCM mixing is performed and output
through S/PDIF, PCM or DAC interfaces, onto the speakers and/or audio
output ports.
Video Decoder & Output
The video PES is parsed, and the video ES is passed to the video bit
buffers. Then video decoding is performed and the display frame buffers
generated are presented on the video display layers, which are then
composited by the video/graphics mixer for final presentation onto the
panel and/or video output ports.
PVR/DVR & Stored Media Playback (shown in green)
Takes care of recording of live content, playback of recorded content,
buffering (pause/review), movie-on-demand/VOD, Ad-insertions, USB
media playback, etc.
Closed Captions, Sub-titles, Teletext
Allows text data to be embedded into the video, for foreign language
movie viewing, aiding hearing-impaired people, news/weather/score
updates, etc.
PSI/SI, EPG, DSMCC, OTA upgrade, Graphics
The applications and middleware uses these modules extensively for
value-added features such as showing the program guide, service
