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TAV-DT format revision and soft sync recovery

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minjaesong
2025-12-15 17:42:08 +09:00
parent 3d76006ad9
commit 4929d84cec
4 changed files with 189 additions and 37 deletions
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23
video_encoder/src/encoder_tav_dt.c
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@@ -9,15 +9,16 @@
* - Mandatory TAD audio
* - LDPC rate 1/2 for headers, Reed-Solomon (255,223) for payloads
*
* Packet structure (revised 2025-12-11):
* Packet structure (revised 2025-12-15):
* - Main header: 28 bytes -> 56 bytes LDPC encoded
* (sync + fps + flags + reserved + size + crc + timecode + offset_to_video)
* Layout: sync(4) + fps(1) + flags(1) + reserved(2) + size(4) + timecode(8) + offset(4) + crc(4)
* CRC covers bytes 0-23 (everything except CRC itself)
* - TAD subpacket: header (10->20 bytes LDPC) + RS-encoded payload
* - TAV subpacket: header (8->16 bytes LDPC) + RS-encoded payload
* - No packet type bytes - always audio then video
*
* Created by CuriousTorvald and Claude on 2025-12-09.
* Revised 2025-12-11 for updated TAV-DT specification.
* Revised 2025-12-15 for updated TAV-DT specification (CRC now covers timecode and offset).
*/
#define _POSIX_C_SOURCE 200809L
@@ -299,6 +300,8 @@ static int write_packet(dt_encoder_t *enc, uint64_t timecode_ns,
uint32_t packet_size = tad_subpacket_size + tav_subpacket_size;
// Build main header (28 bytes)
// Layout (revised 2025-12-15): sync(4) + fps(1) + flags(1) + reserved(2) + size(4) + timecode(8) + offset(4) + crc(4)
// CRC is calculated over bytes 0-23 (everything except CRC itself)
uint8_t header[DT_MAIN_HEADER_SIZE];
// Write sync pattern in big-endian (network byte order)
uint32_t sync = enc->is_pal ? TAV_DT_SYNC_PAL : TAV_DT_SYNC_NTSC;
@@ -328,15 +331,15 @@ static int write_packet(dt_encoder_t *enc, uint64_t timecode_ns,
// Packet size (4 bytes)
memcpy(header + 8, &packet_size, 4);
// CRC placeholder (will be calculated over header bytes 0-11)
uint32_t crc = calculate_crc32(header, 12);
memcpy(header + 12, &crc, 4);
// Timecode (8 bytes) - now at offset 12
memcpy(header + 12, &timecode_ns, 8);
// Timecode (8 bytes)
memcpy(header + 16, &timecode_ns, 8);
// Offset to video (4 bytes) - now at offset 20
memcpy(header + 20, &offset_to_video, 4);
// Offset to video (4 bytes)
memcpy(header + 24, &offset_to_video, 4);
// CRC-32 (4 bytes) - calculated over bytes 0-23 (sync + fps + flags + reserved + size + timecode + offset)
uint32_t crc = calculate_crc32(header, 24);
memcpy(header + 24, &crc, 4);
// LDPC encode main header
uint8_t ldpc_header[DT_MAIN_HEADER_SIZE * 2];