Samsung DSB-S300G Service Manual page 81

Circuit Operating Descriptions
2) Programmable transport interface (PTI)
The PTI performs transport-stream descrambling, demultiplexing and data filtering. PES
data is transferred by DMA to audio and video decoders using circular buffers. Section
data is transferred by DMA to separate buffers for further processing by the CPU.
DIRECTV and DVB transport streams can be handled by the PTI with data rates up to
138 Mbit/s.
The PTI performs PID filtering to select audio, video and data packets to be processed.
96 PID slots can be supported by the PTI.
The PTI can descramble streams using the following ciphers:
• DES-ECB,
• DES-CBC including DVS-042 and cipher text stealing termination block handling,
• DVB-CSA,
• NDS specific streams can also be supported for integrated ICAM functionality.
The PTI has a section filter core that filters DVB and DIRECTV standard sections. Four
filtering modes are available:
• wide match mode: 48x 16-byte filters,
• long match mode: 96x 8-byte filters,
• positive/negative mode: 48x 8-byte filters with positive/negative filtering at the bit level.
Matching sections are transferred to memory buffers for processing by software.
When the PTI is required to output a transport stream, it can output the entire
transport stream or selected packets filtered by PID. A latency counter is provided to
ensure packet timing is preserved. Packet substitution can also be performed.
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