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314 lines
12 KiB
XML
314 lines
12 KiB
XML
<section id="isdbt">
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<title>ISDB-T frontend</title>
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<para>This section describes shortly what are the possible parameters in the Linux
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DVB-API called "S2API" and now DVB API 5 in order to tune an ISDB-T/ISDB-Tsb
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demodulator:</para>
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<para>This ISDB-T/ISDB-Tsb API extension should reflect all information
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needed to tune any ISDB-T/ISDB-Tsb hardware. Of course it is possible
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that some very sophisticated devices won't need certain parameters to
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tune.</para>
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<para>The information given here should help application writers to know how
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to handle ISDB-T and ISDB-Tsb hardware using the Linux DVB-API.</para>
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<para>The details given here about ISDB-T and ISDB-Tsb are just enough to
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basically show the dependencies between the needed parameter values,
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but surely some information is left out. For more detailed information
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see the following documents:</para>
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<para>ARIB STD-B31 - "Transmission System for Digital Terrestrial
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Television Broadcasting" and</para>
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<para>ARIB TR-B14 - "Operational Guidelines for Digital Terrestrial
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Television Broadcasting".</para>
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<para>In order to read this document one has to have some knowledge the
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channel structure in ISDB-T and ISDB-Tsb. I.e. it has to be known to
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the reader that an ISDB-T channel consists of 13 segments, that it can
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have up to 3 layer sharing those segments, and things like that.</para>
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<para>Parameters used by ISDB-T and ISDB-Tsb.</para>
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<section id="isdbt-parms">
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<title>Parameters that are common with DVB-T and ATSC</title>
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<section id="isdbt-freq">
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<title><constant>DTV_FREQUENCY</constant></title>
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<para>Central frequency of the channel.</para>
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<para>For ISDB-T the channels are usally transmitted with an offset of 143kHz. E.g. a
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valid frequncy could be 474143 kHz. The stepping is bound to the bandwidth of
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the channel which is 6MHz.</para>
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<para>As in ISDB-Tsb the channel consists of only one or three segments the
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frequency step is 429kHz, 3*429 respectively. As for ISDB-T the
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central frequency of the channel is expected.</para>
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</section>
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<section id="isdbt-bw">
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<title><constant>DTV_BANDWIDTH_HZ</constant> (optional)</title>
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<para>Possible values:</para>
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<para>For ISDB-T it should be always 6000000Hz (6MHz)</para>
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<para>For ISDB-Tsb it can vary depending on the number of connected segments</para>
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<para>Note: Hardware specific values might be given here, but standard
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applications should not bother to set a value to this field as
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standard demods are ignoring it anyway.</para>
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<para>Bandwidth in ISDB-T is fixed (6MHz) or can be easily derived from
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other parameters (DTV_ISDBT_SB_SEGMENT_IDX,
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DTV_ISDBT_SB_SEGMENT_COUNT).</para>
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</section>
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<section id="isdbt-delivery-sys">
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<title><constant>DTV_DELIVERY_SYSTEM</constant></title>
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<para>Possible values: <constant>SYS_ISDBT</constant></para>
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</section>
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<section id="isdbt-tx-mode">
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<title><constant>DTV_TRANSMISSION_MODE</constant></title>
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<para>ISDB-T supports three carrier/symbol-size: 8K, 4K, 2K. It is called
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'mode' in the standard: Mode 1 is 2K, mode 2 is 4K, mode 3 is 8K</para>
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<para>Possible values: <constant>TRANSMISSION_MODE_2K</constant>, <constant>TRANSMISSION_MODE_8K</constant>,
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<constant>TRANSMISSION_MODE_AUTO</constant>, <constant>TRANSMISSION_MODE_4K</constant></para>
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<para>If <constant>DTV_TRANSMISSION_MODE</constant> is set the <constant>TRANSMISSION_MODE_AUTO</constant> the
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hardware will try to find the correct FFT-size (if capable) and will
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use TMCC to fill in the missing parameters.</para>
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<para><constant>TRANSMISSION_MODE_4K</constant> is added at the same time as the other new parameters.</para>
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</section>
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<section id="isdbt-guard-interval">
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<title><constant>DTV_GUARD_INTERVAL</constant></title>
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<para>Possible values: <constant>GUARD_INTERVAL_1_32</constant>, <constant>GUARD_INTERVAL_1_16</constant>, <constant>GUARD_INTERVAL_1_8</constant>,
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<constant>GUARD_INTERVAL_1_4</constant>, <constant>GUARD_INTERVAL_AUTO</constant></para>
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<para>If <constant>DTV_GUARD_INTERVAL</constant> is set the <constant>GUARD_INTERVAL_AUTO</constant> the hardware will
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try to find the correct guard interval (if capable) and will use TMCC to fill
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in the missing parameters.</para>
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</section>
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</section>
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<section id="isdbt-new-parms">
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<title>ISDB-T only parameters</title>
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<section id="isdbt-part-rec">
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<title><constant>DTV_ISDBT_PARTIAL_RECEPTION</constant></title>
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<para><constant>If DTV_ISDBT_SOUND_BROADCASTING</constant> is '0' this bit-field represents whether
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the channel is in partial reception mode or not.</para>
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<para>If '1' <constant>DTV_ISDBT_LAYERA_*</constant> values are assigned to the center segment and
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<constant>DTV_ISDBT_LAYERA_SEGMENT_COUNT</constant> has to be '1'.</para>
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<para>If in addition <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'
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<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> represents whether this ISDB-Tsb channel
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is consisting of one segment and layer or three segments and two layers.</para>
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<para>Possible values: 0, 1, -1 (AUTO)</para>
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</section>
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<section id="isdbt-sound-bcast">
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<title><constant>DTV_ISDBT_SOUND_BROADCASTING</constant></title>
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<para>This field represents whether the other DTV_ISDBT_*-parameters are
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referring to an ISDB-T and an ISDB-Tsb channel. (See also
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<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>).</para>
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<para>Possible values: 0, 1, -1 (AUTO)</para>
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</section>
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<section id="isdbt-sb-ch-id">
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<title><constant>DTV_ISDBT_SB_SUBCHANNEL_ID</constant></title>
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<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>
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<para>(Note of the author: This might not be the correct description of the
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<constant>SUBCHANNEL-ID</constant> in all details, but it is my understanding of the technical
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background needed to program a device)</para>
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<para>An ISDB-Tsb channel (1 or 3 segments) can be broadcasted alone or in a
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set of connected ISDB-Tsb channels. In this set of channels every
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channel can be received independently. The number of connected
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ISDB-Tsb segment can vary, e.g. depending on the frequency spectrum
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bandwidth available.</para>
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<para>Example: Assume 8 ISDB-Tsb connected segments are broadcasted. The
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broadcaster has several possibilities to put those channels in the
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air: Assuming a normal 13-segment ISDB-T spectrum he can align the 8
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segments from position 1-8 to 5-13 or anything in between.</para>
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<para>The underlying layer of segments are subchannels: each segment is
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consisting of several subchannels with a predefined IDs. A sub-channel
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is used to help the demodulator to synchronize on the channel.</para>
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<para>An ISDB-T channel is always centered over all sub-channels. As for
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the example above, in ISDB-Tsb it is no longer as simple as that.</para>
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<para><constant>The DTV_ISDBT_SB_SUBCHANNEL_ID</constant> parameter is used to give the
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sub-channel ID of the segment to be demodulated.</para>
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<para>Possible values: 0 .. 41, -1 (AUTO)</para>
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</section>
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<section id="isdbt-sb-seg-idx">
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<title><constant>DTV_ISDBT_SB_SEGMENT_IDX</constant></title>
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<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>
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<para><constant>DTV_ISDBT_SB_SEGMENT_IDX</constant> gives the index of the segment to be
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demodulated for an ISDB-Tsb channel where several of them are
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transmitted in the connected manner.</para>
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<para>Possible values: 0 .. <constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant> - 1</para>
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<para>Note: This value cannot be determined by an automatic channel search.</para>
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</section>
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<section id="isdbt-sb-seg-cnt">
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<title><constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant></title>
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<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>
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<para><constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant> gives the total count of connected ISDB-Tsb
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channels.</para>
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<para>Possible values: 1 .. 13</para>
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<para>Note: This value cannot be determined by an automatic channel search.</para>
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</section>
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<section id="isdb-hierq-layers">
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<title>Hierarchical layers</title>
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<para>ISDB-T channels can be coded hierarchically. As opposed to DVB-T in
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ISDB-T hierarchical layers can be decoded simultaneously. For that
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reason a ISDB-T demodulator has 3 viterbi and 3 reed-solomon-decoders.</para>
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<para>ISDB-T has 3 hierarchical layers which each can use a part of the
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available segments. The total number of segments over all layers has
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to 13 in ISDB-T.</para>
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<section id="isdbt-layer-ena">
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<title><constant>DTV_ISDBT_LAYER_ENABLED</constant></title>
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<para>Hierarchical reception in ISDB-T is achieved by enabling or disabling
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layers in the decoding process. Setting all bits of
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<constant>DTV_ISDBT_LAYER_ENABLED</constant> to '1' forces all layers (if applicable) to be
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demodulated. This is the default.</para>
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<para>If the channel is in the partial reception mode
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(<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> = 1) the central segment can be decoded
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independently of the other 12 segments. In that mode layer A has to
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have a <constant>SEGMENT_COUNT</constant> of 1.</para>
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<para>In ISDB-Tsb only layer A is used, it can be 1 or 3 in ISDB-Tsb
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according to <constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>. <constant>SEGMENT_COUNT</constant> must be filled
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accordingly.</para>
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<para>Possible values: 0x1, 0x2, 0x4 (|-able)</para>
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<para><constant>DTV_ISDBT_LAYER_ENABLED[0:0]</constant> - layer A</para>
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<para><constant>DTV_ISDBT_LAYER_ENABLED[1:1]</constant> - layer B</para>
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<para><constant>DTV_ISDBT_LAYER_ENABLED[2:2]</constant> - layer C</para>
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<para><constant>DTV_ISDBT_LAYER_ENABLED[31:3]</constant> unused</para>
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</section>
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<section id="isdbt-layer-fec">
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<title><constant>DTV_ISDBT_LAYER*_FEC</constant></title>
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<para>Possible values: <constant>FEC_AUTO</constant>, <constant>FEC_1_2</constant>, <constant>FEC_2_3</constant>, <constant>FEC_3_4</constant>, <constant>FEC_5_6</constant>, <constant>FEC_7_8</constant></para>
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</section>
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<section id="isdbt-layer-mod">
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<title><constant>DTV_ISDBT_LAYER*_MODULATION</constant></title>
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<para>Possible values: <constant>QAM_AUTO</constant>, QP<constant>SK, QAM_16</constant>, <constant>QAM_64</constant>, <constant>DQPSK</constant></para>
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<para>Note: If layer C is <constant>DQPSK</constant> layer B has to be <constant>DQPSK</constant>. If layer B is <constant>DQPSK</constant>
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and <constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>=0 layer has to be <constant>DQPSK</constant>.</para>
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</section>
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<section id="isdbt-layer-seg-cnt">
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<title><constant>DTV_ISDBT_LAYER*_SEGMENT_COUNT</constant></title>
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<para>Possible values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, -1 (AUTO)</para>
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<para>Note: Truth table for <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> and
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<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> and <constant>LAYER</constant>*_SEGMENT_COUNT</para>
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<informaltable id="isdbt-layer_seg-cnt-table">
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<tgroup cols="6">
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<tbody>
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<row>
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<entry>PR</entry>
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<entry>SB</entry>
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<entry>Layer A width</entry>
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<entry>Layer B width</entry>
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<entry>Layer C width</entry>
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<entry>total width</entry>
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</row>
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<row>
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<entry>0</entry>
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<entry>0</entry>
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<entry>1 .. 13</entry>
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<entry>1 .. 13</entry>
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<entry>1 .. 13</entry>
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<entry>13</entry>
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</row>
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<row>
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<entry>1</entry>
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<entry>0</entry>
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<entry>1</entry>
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<entry>1 .. 13</entry>
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<entry>1 .. 13</entry>
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<entry>13</entry>
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</row>
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<row>
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<entry>0</entry>
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<entry>1</entry>
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<entry>1</entry>
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<entry>0</entry>
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<entry>0</entry>
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<entry>1</entry>
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</row>
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<row>
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<entry>1</entry>
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<entry>1</entry>
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<entry>1</entry>
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<entry>2</entry>
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<entry>0</entry>
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<entry>13</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</section>
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<section id="isdbt_layer_t_interl">
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<title><constant>DTV_ISDBT_LAYER*_TIME_INTERLEAVING</constant></title>
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<para>Possible values: 0, 1, 2, 3, -1 (AUTO)</para>
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<para>Note: The real inter-leaver depth-names depend on the mode (fft-size); the values
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here are referring to what can be found in the TMCC-structure -
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independent of the mode.</para>
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</section>
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</section>
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</section>
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</section>
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