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52 lines
2.1 KiB
Plaintext
52 lines
2.1 KiB
Plaintext
- General Information
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The caX device associated with a CI device behaves just like any other
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caX interface. You usually use it through a library like libdvben50221
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which is part of the dvb-apps package available at linuxtv.org.
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But contrary to other hardware where the CI module is physically placed
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in the data path between the the demod and PCIe bridge, in the Digital
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Devices cards the CI module is separate hardware.
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So, you have to feed data to the CI module by writing to the secX
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(in later kernel ci0) device and read it back from the same secX device.
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The advantage is that the CI module can be used with any data coming from
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any frontend or file. The disadvantage is that the user application has to
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write/read the data to/from the module by itself.
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The sample application apps/cit.c shows how to pipe a stream through
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the CI interface. In its ouput it will show discontinuities. Those should
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only occur at the start of the program (due to old packets inside the CI
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interface hardware and the CI module itself) and when a CI module is
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inserted or removed.
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Since some users have problems using standard software which cannot use
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the CI interface in this way, there is now the redirect feature which allows
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you to tell the driver to automatically pass the data coming from one
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demod through a CI before offering it through the normal demux/dvr interface.
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But note that this is a kludge to support old software until they can
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use the new interface.
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See docs/redirect for more info.
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- Clock Speed
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The normal clock speed for the TS output is 72 MHz wich is the standard
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speed used for CI.
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Packets are sent with an adjustable gap between the packets.
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The gap size is (gap value * 2) + 4 or 0 if the gap is disabled.
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So, the standard gap value of 4 leads to a gap of 12 bytes which means
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that the effective data rate is (72*188)/200 = 67.68 MBits/s.
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Depending on the hardware, the clock speed can be changed with the
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ci_bitrate module parameter:
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- Octopus CI, Octopus CI S2 Pro : supported
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- old CI single flex modules: supported
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- new dual CI flex module: not yet supported, use the standard 72000 kHz
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Valid ranges for are from ... to 96000 KHz.
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