<section id="isdbt">
	<title>ISDB-T frontend</title>
	<para>This section describes shortly what are the possible parameters in the Linux
		DVB-API called "S2API" and now DVB API 5 in order to tune an ISDB-T/ISDB-Tsb
		demodulator:</para>

	<para>This ISDB-T/ISDB-Tsb API extension should reflect all information
		needed to tune any ISDB-T/ISDB-Tsb hardware. Of course it is possible
		that some very sophisticated devices won't need certain parameters to
		tune.</para>

	<para>The information given here should help application writers to know how
		to handle ISDB-T and ISDB-Tsb hardware using the Linux DVB-API.</para>

	<para>The details given here about ISDB-T and ISDB-Tsb are just enough to
		basically show the dependencies between the needed parameter values,
		but surely some information is left out. For more detailed information
		see the following documents:</para>

	<para>ARIB STD-B31 - "Transmission System for Digital Terrestrial
		Television Broadcasting" and</para>
	<para>ARIB TR-B14 - "Operational Guidelines for Digital Terrestrial
		Television Broadcasting".</para>

	<para>In order to read this document one has to have some knowledge the
		channel structure in ISDB-T and ISDB-Tsb. I.e. it has to be known to
		the reader that an ISDB-T channel consists of 13 segments, that it can
		have up to 3 layer sharing those segments, and things like that.</para>

	<para>Parameters used by ISDB-T and ISDB-Tsb.</para>

	<section id="isdbt-parms">
		<title>Parameters that are common with DVB-T and ATSC</title>

		<section id="isdbt-freq">
			<title><constant>DTV_FREQUENCY</constant></title>

			<para>Central frequency of the channel.</para>

			<para>For ISDB-T the channels are usally transmitted with an offset of 143kHz. E.g. a
				valid frequncy could be 474143 kHz. The stepping is bound to the bandwidth of
				the channel which is 6MHz.</para>

			<para>As in ISDB-Tsb the channel consists of only one or three segments the
				frequency step is 429kHz, 3*429 respectively. As for ISDB-T the
				central frequency of the channel is expected.</para>
		</section>

		<section id="isdbt-bw">
			<title><constant>DTV_BANDWIDTH_HZ</constant> (optional)</title>

			<para>Possible values:</para>

			<para>For ISDB-T it should be always 6000000Hz (6MHz)</para>
			<para>For ISDB-Tsb it can vary depending on the number of connected segments</para>

			<para>Note: Hardware specific values might be given here, but standard
				applications should not bother to set a value to this field as
				standard demods are ignoring it anyway.</para>

			<para>Bandwidth in ISDB-T is fixed (6MHz) or can be easily derived from
				other parameters (DTV_ISDBT_SB_SEGMENT_IDX,
				DTV_ISDBT_SB_SEGMENT_COUNT).</para>
		</section>

		<section id="isdbt-delivery-sys">
			<title><constant>DTV_DELIVERY_SYSTEM</constant></title>

			<para>Possible values: <constant>SYS_ISDBT</constant></para>
		</section>

		<section id="isdbt-tx-mode">
			<title><constant>DTV_TRANSMISSION_MODE</constant></title>

			<para>ISDB-T supports three carrier/symbol-size: 8K, 4K, 2K. It is called
				'mode' in the standard: Mode 1 is 2K, mode 2 is 4K, mode 3 is 8K</para>

			<para>Possible values: <constant>TRANSMISSION_MODE_2K</constant>, <constant>TRANSMISSION_MODE_8K</constant>,
				<constant>TRANSMISSION_MODE_AUTO</constant>, <constant>TRANSMISSION_MODE_4K</constant></para>

			<para>If <constant>DTV_TRANSMISSION_MODE</constant> is set the <constant>TRANSMISSION_MODE_AUTO</constant> the
				hardware will try to find the correct FFT-size (if capable) and will
				use TMCC to fill in the missing parameters.</para>

			<para><constant>TRANSMISSION_MODE_4K</constant> is added at the same time as the other new parameters.</para>
		</section>

		<section id="isdbt-guard-interval">
			<title><constant>DTV_GUARD_INTERVAL</constant></title>

			<para>Possible values: <constant>GUARD_INTERVAL_1_32</constant>, <constant>GUARD_INTERVAL_1_16</constant>, <constant>GUARD_INTERVAL_1_8</constant>,
				<constant>GUARD_INTERVAL_1_4</constant>, <constant>GUARD_INTERVAL_AUTO</constant></para>

			<para>If <constant>DTV_GUARD_INTERVAL</constant> is set the <constant>GUARD_INTERVAL_AUTO</constant> the hardware will
				try to find the correct guard interval (if capable) and will use TMCC to fill
				in the missing parameters.</para>
		</section>
	</section>
	<section id="isdbt-new-parms">
		<title>ISDB-T only parameters</title>

		<section id="isdbt-part-rec">
			<title><constant>DTV_ISDBT_PARTIAL_RECEPTION</constant></title>

			<para><constant>If DTV_ISDBT_SOUND_BROADCASTING</constant> is '0' this bit-field represents whether
				the channel is in partial reception mode or not.</para>

			<para>If '1' <constant>DTV_ISDBT_LAYERA_*</constant> values are assigned to the center segment and
				<constant>DTV_ISDBT_LAYERA_SEGMENT_COUNT</constant> has to be '1'.</para>

			<para>If in addition <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'
				<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> represents whether this ISDB-Tsb channel
				is consisting of one segment and layer or three segments and two layers.</para>

			<para>Possible values: 0, 1, -1 (AUTO)</para>
		</section>

		<section id="isdbt-sound-bcast">
			<title><constant>DTV_ISDBT_SOUND_BROADCASTING</constant></title>

			<para>This field represents whether the other DTV_ISDBT_*-parameters are
				referring to an ISDB-T and an ISDB-Tsb channel. (See also
				<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>).</para>

			<para>Possible values: 0, 1, -1 (AUTO)</para>
		</section>

		<section id="isdbt-sb-ch-id">
			<title><constant>DTV_ISDBT_SB_SUBCHANNEL_ID</constant></title>

			<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>

			<para>(Note of the author: This might not be the correct description of the
				<constant>SUBCHANNEL-ID</constant> in all details, but it is my understanding of the technical
				background needed to program a device)</para>

			<para>An ISDB-Tsb channel (1 or 3 segments) can be broadcasted alone or in a
				set of connected ISDB-Tsb channels. In this set of channels every
				channel can be received independently. The number of connected
				ISDB-Tsb segment can vary, e.g. depending on the frequency spectrum
				bandwidth available.</para>

			<para>Example: Assume 8 ISDB-Tsb connected segments are broadcasted. The
				broadcaster has several possibilities to put those channels in the
				air: Assuming a normal 13-segment ISDB-T spectrum he can align the 8
				segments from position 1-8 to 5-13 or anything in between.</para>

			<para>The underlying layer of segments are subchannels: each segment is
				consisting of several subchannels with a predefined IDs. A sub-channel
				is used to help the demodulator to synchronize on the channel.</para>

			<para>An ISDB-T channel is always centered over all sub-channels. As for
				the example above, in ISDB-Tsb it is no longer as simple as that.</para>

			<para><constant>The DTV_ISDBT_SB_SUBCHANNEL_ID</constant> parameter is used to give the
				sub-channel ID of the segment to be demodulated.</para>

			<para>Possible values: 0 .. 41, -1 (AUTO)</para>
		</section>

		<section id="isdbt-sb-seg-idx">

			<title><constant>DTV_ISDBT_SB_SEGMENT_IDX</constant></title>

			<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>

			<para><constant>DTV_ISDBT_SB_SEGMENT_IDX</constant> gives the index of the segment to be
				demodulated for an ISDB-Tsb channel where several of them are
				transmitted in the connected manner.</para>

			<para>Possible values: 0 .. <constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant> - 1</para>

			<para>Note: This value cannot be determined by an automatic channel search.</para>
		</section>

		<section id="isdbt-sb-seg-cnt">
			<title><constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant></title>

			<para>This field only applies if <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> is '1'.</para>

			<para><constant>DTV_ISDBT_SB_SEGMENT_COUNT</constant> gives the total count of connected ISDB-Tsb
				channels.</para>

			<para>Possible values: 1 .. 13</para>

			<para>Note: This value cannot be determined by an automatic channel search.</para>
		</section>

		<section id="isdb-hierq-layers">
			<title>Hierarchical layers</title>

			<para>ISDB-T channels can be coded hierarchically. As opposed to DVB-T in
				ISDB-T hierarchical layers can be decoded simultaneously. For that
				reason a ISDB-T demodulator has 3 viterbi and 3 reed-solomon-decoders.</para>

			<para>ISDB-T has 3 hierarchical layers which each can use a part of the
				available segments. The total number of segments over all layers has
				to 13 in ISDB-T.</para>

			<section id="isdbt-layer-ena">
				<title><constant>DTV_ISDBT_LAYER_ENABLED</constant></title>

				<para>Hierarchical reception in ISDB-T is achieved by enabling or disabling
					layers in the decoding process. Setting all bits of
					<constant>DTV_ISDBT_LAYER_ENABLED</constant> to '1' forces all layers (if applicable) to be
					demodulated. This is the default.</para>

				<para>If the channel is in the partial reception mode
					(<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> = 1) the central segment can be decoded
					independently of the other 12 segments. In that mode layer A has to
					have a <constant>SEGMENT_COUNT</constant> of 1.</para>

				<para>In ISDB-Tsb only layer A is used, it can be 1 or 3 in ISDB-Tsb
					according to <constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>. <constant>SEGMENT_COUNT</constant> must be filled
					accordingly.</para>

				<para>Possible values: 0x1, 0x2, 0x4 (|-able)</para>

				<para><constant>DTV_ISDBT_LAYER_ENABLED[0:0]</constant> - layer A</para>
				<para><constant>DTV_ISDBT_LAYER_ENABLED[1:1]</constant> - layer B</para>
				<para><constant>DTV_ISDBT_LAYER_ENABLED[2:2]</constant> - layer C</para>
				<para><constant>DTV_ISDBT_LAYER_ENABLED[31:3]</constant> unused</para>
			</section>

			<section id="isdbt-layer-fec">
				<title><constant>DTV_ISDBT_LAYER*_FEC</constant></title>

				<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>
			</section>

			<section id="isdbt-layer-mod">
				<title><constant>DTV_ISDBT_LAYER*_MODULATION</constant></title>

				<para>Possible values: <constant>QAM_AUTO</constant>, QP<constant>SK, QAM_16</constant>, <constant>QAM_64</constant>, <constant>DQPSK</constant></para>

				<para>Note: If layer C is <constant>DQPSK</constant> layer B has to be <constant>DQPSK</constant>. If layer B is <constant>DQPSK</constant>
					and <constant>DTV_ISDBT_PARTIAL_RECEPTION</constant>=0 layer has to be <constant>DQPSK</constant>.</para>
			</section>

			<section id="isdbt-layer-seg-cnt">
				<title><constant>DTV_ISDBT_LAYER*_SEGMENT_COUNT</constant></title>

				<para>Possible values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, -1 (AUTO)</para>

				<para>Note: Truth table for <constant>DTV_ISDBT_SOUND_BROADCASTING</constant> and
					<constant>DTV_ISDBT_PARTIAL_RECEPTION</constant> and <constant>LAYER</constant>*_SEGMENT_COUNT</para>

				<informaltable id="isdbt-layer_seg-cnt-table">
					<tgroup cols="6">

						<tbody>
							<row>
								<entry>PR</entry>
								<entry>SB</entry>
								<entry>Layer A width</entry>
								<entry>Layer B width</entry>
								<entry>Layer C width</entry>
								<entry>total width</entry>
							</row>

							<row>
								<entry>0</entry>
								<entry>0</entry>
								<entry>1 .. 13</entry>
								<entry>1 .. 13</entry>
								<entry>1 .. 13</entry>
								<entry>13</entry>
							</row>

							<row>
								<entry>1</entry>
								<entry>0</entry>
								<entry>1</entry>
								<entry>1 .. 13</entry>
								<entry>1 .. 13</entry>
								<entry>13</entry>
							</row>

							<row>
								<entry>0</entry>
								<entry>1</entry>
								<entry>1</entry>
								<entry>0</entry>
								<entry>0</entry>
								<entry>1</entry>
							</row>

							<row>
								<entry>1</entry>
								<entry>1</entry>
								<entry>1</entry>
								<entry>2</entry>
								<entry>0</entry>
								<entry>13</entry>
							</row>
						</tbody>

					</tgroup>
				</informaltable>

			</section>

			<section id="isdbt_layer_t_interl">
				<title><constant>DTV_ISDBT_LAYER*_TIME_INTERLEAVING</constant></title>

				<para>Possible values: 0, 1, 2, 3, -1 (AUTO)</para>

				<para>Note: The real inter-leaver depth-names depend on the mode (fft-size); the values
					here are referring to what can be found in the TMCC-structure -
					independent of the mode.</para>
			</section>
		</section>
	</section>
</section>