Method and apparatus for formatting data signals in a digital audio broadcasting system
View Patent ↗A data unit for transmitting data in a digital broadcasting system includes a first payload field, and a first byte code field having a value indicating an offset of data in the first payload field with respect to an absent value. A method for formatting the data unit includes: providing data for a payload field for a data unit, wherein the data includes an absent byte value, determining an offset between an absent byte value and other data in the payload field, shifting the data in the payload field by the offset to produce shifted bytes, and inserting a byte code in the data unit, wherein the byte code indicates the offset. A transmitter for transmitting the data units, and a receiver for receiving the data units are also provided.
1. A transmitter for broadcasting a digital radio signal, the transmitter comprising:
a processor for receiving a plurality of data bytes in a block of payload data; identifying two adjacent byte values that do not appear in the block of payload data; calculating an offset between the two adjacent byte values and two adjacent control values; shifting the values of the plurality of data bytes by the offset to produce shifted bytes; inserting a byte code and the shifted bytes in a data unit to produce a modified data unit that does not include escape values, wherein the byte code indicates the offset; and inserting a plurality of additional byte code fields and a plurality of additional shifted bytes in the modified data unit, wherein each of the additional byte code fields indicates an offset of data in one of the plurality of additional shifted bytes; and
a modulator for using the modified data unit to modulate a plurality of carriers to produce an output signal.
2. The transmitter of claim 1 , wherein the processor inserts a start flag field, a protocol ID field, a port number field, a sequence number field, and a frame check sequence field in the modified data unit.
3. The transmitter of claim 1 , wherein the processor inserts a frame number field and a frame total field in the modified data unit.
4. The transmitter of claim 1 , wherein the processor removes reserved byte values from the payload field.
5. A digital radio receiver comprising:
an input for receiving a plurality of carriers modulated by a plurality of payload data units that do not include escape values, each data unit including a plurality of payload data byte values shifted by an offset between two adjacent byte values that do not appear in the payload data unit and two adjacent control values; and a byte code, wherein the byte code indicates the offset; and
a processor for using the data units to produce an output signal, wherein the data unit further comprises a start flag field; a protocol ID field; a port number field; a sequence number field; a frame check sequence field; a frame number field; a frame total field; a plurality of additional byte code fields; and a plurality of additional shifted bytes, wherein each of the additional byte code fields indicates an offset of data in one of the plurality of additional shifted bytes.
6. The receiver of claim 5 , wherein the processor uses the additional byte code fields, the frame number field and the frame total field to reassemble the shifted bytes.
7. An apparatus comprising:
an input for receiving a plurality of blocks of bytes of payload data, each byte having a value;
a processor that calculates an offset between two byte values that do not appear in the block of payload data and two adjacent control values; subtracts the offset from the value of each of the bytes of data to produce modified data bytes in a plurality of data units that do not include escape values; inserts a start flag field, a protocol ID field, a port number field, a sequence number field, and a frame check sequence field in a data unit including the modified data bytes; and inserts a plurality of additional byte code fields and a plurality of additional shifted bytes in the data unit, wherein each of the additional byte code fields indicates an offset of data in one of the plurality of additional shifted bytes; and
a transmitter that transmits the data units including the modified data bytes and the offset to a receiver.
8. The apparatus of claim 7 , wherein the processor inserts a frame number field and a frame total field in the data unit.
9. The apparatus of claim 7 , wherein the two adjacent control values are 0x7D and 0x7E.
10. The apparatus of claim 7 , wherein the plurality of bytes consist of 127 bytes of 8-bit data.