HD Caption Legalizer / Relocating Bridge MODEL ... - EEG Enterprises
HD Caption Legalizer / Relocating Bridge MODEL ... - EEG Enterprises
HD Caption Legalizer / Relocating Bridge MODEL ... - EEG Enterprises
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CB512 <strong>HD</strong> <strong>Caption</strong> <strong>Legalizer</strong> / <strong>Relocating</strong> <strong>Bridge</strong>eegAppendicesAppendix A: Grand Alliance Interface ProtocolThe following table describes the Data Packet Structure used by <strong>EEG</strong>equipment to send caption data to Grand Alliance protocol ATSC encoders.This protocol has been proven compatible with encoders from all majormanufacturers supporting GA protocol.Byte Name Value Meaning0 SOH 0x01 ASCII SOH, start of packet1 Type0x410x310x32ASCII “A”, ATVCC dataASCII “1”, NTSC field 1 dataASCII “2”, NTSC field 2 data2 Count 5+n Packet size, in bytes, including headerand trailer bytes.3 Data 14 Data 22+n Data nEIA-708 data bytes.3+n Checksum 1 byte checksum. The sum of all bytesin the packet must be zero, modulo256.4+n EOT 0x04 ASCII EOT, end of packetNotes:1. The maximum packet size is 128 (0x80).2. Because the packet size (Count) includes the header and trailer bytes, theminimum valid count is 5. This corresponds to a packet with zero databytes.3. This packet structure is applied only to the data for the closed caption serialstream input to the ATSC encoder. Outgoing bytes in the ATSC streamfollow the EIA-708B standard.©2009-2011 <strong>EEG</strong> <strong>Enterprises</strong>, Inc. 17
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