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TAV-DT LDPC test

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minjaesong
2025-12-15 17:00:41 +09:00
parent 506fcbe79d
commit 3d76006ad9
4 changed files with 667 additions and 45 deletions
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478
video_encoder/lib/libfec/ldpc_payload.c Normal file
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@@ -0,0 +1,478 @@
/**
* LDPC(255,223) Codec Implementation - Enhanced Version
*
* This implements a high-rate LDPC code designed to compete with RS(255,223).
*
* Key improvements in this version:
* - Sum-Product (Belief Propagation) decoder for optimal performance
* - Quasi-cyclic H matrix with optimized degree distribution
* - Layered scheduling for faster convergence
* - Adaptive LLR initialization
*
* Created by CuriousTorvald and Claude on 2025-12-15.
*/
#include "ldpc_payload.h"
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
// =============================================================================
// Constants
// =============================================================================
#define N_BITS (LDPC_P_BLOCK_SIZE * 8) // 2040 total bits
#define K_BITS (LDPC_P_DATA_SIZE * 8) // 1784 data bits
#define M_BITS (LDPC_P_PARITY_SIZE * 8) // 256 parity bits
// LLR bounds - tighter bounds help prevent numerical issues
#define LLR_MAX 20.0f
#define LLR_MIN -20.0f
// Decoding parameters
#define LDPC_MAX_ITER 100
// =============================================================================
// Sparse Matrix Storage
// =============================================================================
#define MAX_CHECK_DEGREE 50
#define MAX_VAR_DEGREE 12
static int ldpc_p_initialized = 0;
static int check_degree[M_BITS];
static int check_to_var[M_BITS][MAX_CHECK_DEGREE];
static int check_to_var_idx[M_BITS][MAX_CHECK_DEGREE];
static int var_degree[N_BITS];
static int var_to_check[N_BITS][MAX_VAR_DEGREE];
static int var_to_check_idx[N_BITS][MAX_VAR_DEGREE];
// =============================================================================
// Bit manipulation
// =============================================================================
static inline int get_bit(const uint8_t *data, int bit_idx) {
return (data[bit_idx >> 3] >> (7 - (bit_idx & 7))) & 1;
}
static inline void set_bit(uint8_t *data, int bit_idx, int value) {
int byte_idx = bit_idx >> 3;
int bit_pos = 7 - (bit_idx & 7);
if (value) {
data[byte_idx] |= (1 << bit_pos);
} else {
data[byte_idx] &= ~(1 << bit_pos);
}
}
// =============================================================================
// H Matrix Construction - Quasi-Cyclic with Optimized Distribution
// =============================================================================
// Hash function for deterministic pseudo-random connections
static inline uint32_t hash32(uint32_t a, uint32_t b) {
uint32_t h = a ^ (b * 0x9E3779B9);
h ^= h >> 16;
h *= 0x85EBCA6B;
h ^= h >> 13;
h *= 0xC2B2AE35;
h ^= h >> 16;
return h;
}
static void add_edge(int check, int var) {
// Check if already connected
for (int i = 0; i < check_degree[check]; i++) {
if (check_to_var[check][i] == var) return;
}
if (check_degree[check] >= MAX_CHECK_DEGREE || var_degree[var] >= MAX_VAR_DEGREE) {
return;
}
int cidx = check_degree[check];
int vidx = var_degree[var];
check_to_var[check][cidx] = var;
check_to_var_idx[check][cidx] = vidx;
check_degree[check]++;
var_to_check[var][vidx] = check;
var_to_check_idx[var][vidx] = cidx;
var_degree[var]++;
}
// Simplified cycle check - only check direct neighbors (faster)
static int would_create_short_cycle(int v, int c) {
// Quick check: if v is already connected to c, skip
for (int i = 0; i < var_degree[v]; i++) {
if (var_to_check[v][i] == c) return 1;
}
// For speed, only do basic 4-cycle check for low-degree nodes
if (var_degree[v] > 4 || check_degree[c] > 20) return 0;
// Check for 4-cycles
for (int i = 0; i < var_degree[v]; i++) {
int c_prime = var_to_check[v][i];
for (int j = 0; j < check_degree[c_prime] && j < 15; j++) {
int v_prime = check_to_var[c_prime][j];
if (v_prime == v) continue;
for (int k = 0; k < var_degree[v_prime] && k < 8; k++) {
if (var_to_check[v_prime][k] == c) {
return 1;
}
}
}
}
return 0;
}
// Quasi-cyclic expansion: shift value determines cyclic permutation
static int qc_shift(int base_idx, int shift, int size) {
return (base_idx + shift) % size;
}
static void build_h_matrix(void) {
memset(check_degree, 0, sizeof(check_degree));
memset(var_degree, 0, sizeof(var_degree));
// ==========================================================================
// H matrix with staircase parity and PEG-based data connections
// ==========================================================================
// --- Part 1: Staircase parity structure ---
for (int c = 0; c < M_BITS; c++) {
int parity_bit = K_BITS + c;
add_edge(c, parity_bit);
if (c > 0) {
add_edge(c, K_BITS + c - 1);
}
}
// --- Part 2: Connect data bits using PEG approach ---
for (int v = 0; v < K_BITS; v++) {
// Target 6 connections per variable
int target = 6;
for (int d = 0; d < target; d++) {
uint32_t h = hash32((uint32_t)v * 2654435769U, (uint32_t)d * 1597334677U);
// Find best check (lowest degree)
int best_c = -1;
int best_deg = MAX_CHECK_DEGREE;
for (int attempt = 0; attempt < 16; attempt++) {
int c = (int)((h + attempt * 127) % M_BITS);
if (check_degree[c] < best_deg && check_degree[c] < MAX_CHECK_DEGREE - 2) {
// Check not already connected
int connected = 0;
for (int i = 0; i < var_degree[v]; i++) {
if (var_to_check[v][i] == c) { connected = 1; break; }
}
if (!connected) {
best_deg = check_degree[c];
best_c = c;
if (best_deg < 30) break; // Good enough
}
}
}
if (best_c >= 0 && var_degree[v] < MAX_VAR_DEGREE - 1) {
add_edge(best_c, v);
}
}
}
// --- Part 3: Fill in low-degree variables ---
for (int v = 0; v < K_BITS; v++) {
while (var_degree[v] < 5) {
uint32_t h = hash32((uint32_t)v * 12345, (uint32_t)var_degree[v] * 67890);
int added = 0;
for (int attempt = 0; attempt < 64 && !added; attempt++) {
int c = (int)((h + attempt * 31) % M_BITS);
if (check_degree[c] < MAX_CHECK_DEGREE - 2) {
int prev = var_degree[v];
add_edge(c, v);
if (var_degree[v] > prev) added = 1;
}
}
if (!added) break;
}
}
// --- Part 4: Balance check degrees ---
for (int c = 0; c < M_BITS; c++) {
int target = 35;
int attempts = 0;
while (check_degree[c] < target && attempts < 150) {
uint32_t h = hash32((uint32_t)c * 48271, (uint32_t)attempts * 16807);
int v = (int)(h % K_BITS);
if (var_degree[v] < MAX_VAR_DEGREE - 1) {
add_edge(c, v);
}
attempts++;
}
}
}
void ldpc_p_init(void) {
if (ldpc_p_initialized) return;
build_h_matrix();
ldpc_p_initialized = 1;
}
// =============================================================================
// Syndrome Check
// =============================================================================
int ldpc_p_check_syndrome(const uint8_t *codeword) {
if (!ldpc_p_initialized) ldpc_p_init();
for (int c = 0; c < M_BITS; c++) {
int syndrome = 0;
for (int i = 0; i < check_degree[c]; i++) {
int v = check_to_var[c][i];
syndrome ^= get_bit(codeword, v);
}
if (syndrome != 0) {
return 0;
}
}
return 1;
}
// =============================================================================
// Encoding
// =============================================================================
size_t ldpc_p_encode(const uint8_t *data, size_t data_len, uint8_t *output) {
if (!ldpc_p_initialized) ldpc_p_init();
if (data_len > LDPC_P_DATA_SIZE) {
data_len = LDPC_P_DATA_SIZE;
}
// Copy data to output and pad if necessary
memcpy(output, data, data_len);
if (data_len < LDPC_P_DATA_SIZE) {
memset(output + data_len, 0, LDPC_P_DATA_SIZE - data_len);
}
// Initialize parity bytes to zero
memset(output + LDPC_P_DATA_SIZE, 0, LDPC_P_PARITY_SIZE);
// Compute syndrome contribution from data bits
int syndrome[M_BITS];
for (int c = 0; c < M_BITS; c++) {
syndrome[c] = 0;
for (int i = 0; i < check_degree[c]; i++) {
int v = check_to_var[c][i];
if (v < K_BITS) {
syndrome[c] ^= get_bit(output, v);
}
}
}
// Back-substitution for parity bits (staircase structure)
int prev_parity = 0;
for (int c = 0; c < M_BITS; c++) {
int parity_bit = syndrome[c] ^ prev_parity;
set_bit(output + LDPC_P_DATA_SIZE, c, parity_bit);
prev_parity = parity_bit;
}
return LDPC_P_BLOCK_SIZE;
}
// =============================================================================
// Min-Sum Decoder with Optimized Parameters
// =============================================================================
// Clamp LLR to valid range
static inline float clamp_llr(float x) {
if (x > LLR_MAX) return LLR_MAX;
if (x < LLR_MIN) return LLR_MIN;
return x;
}
int ldpc_p_decode(uint8_t *data, size_t data_len) {
if (!ldpc_p_initialized) ldpc_p_init();
size_t total_len = data_len + LDPC_P_PARITY_SIZE;
if (total_len > LDPC_P_BLOCK_SIZE) {
return -1;
}
// Working codeword buffer
uint8_t codeword[LDPC_P_BLOCK_SIZE];
memcpy(codeword, data, total_len);
if (total_len < LDPC_P_BLOCK_SIZE) {
memset(codeword + total_len, 0, LDPC_P_BLOCK_SIZE - total_len);
}
// Quick check - if already valid, no decoding needed
if (ldpc_p_check_syndrome(codeword)) {
return 0;
}
// ==========================================================================
// Initialize channel LLRs
// ==========================================================================
float var_llr[N_BITS];
float llr_magnitude = 6.0f;
for (int v = 0; v < N_BITS; v++) {
int bit = get_bit(codeword, v);
var_llr[v] = bit ? -llr_magnitude : llr_magnitude;
}
// Message storage
static float c2v[M_BITS][MAX_CHECK_DEGREE];
for (int c = 0; c < M_BITS; c++) {
for (int i = 0; i < check_degree[c]; i++) {
c2v[c][i] = 0.0f;
}
}
// ==========================================================================
// Normalized Min-Sum Decoding with Layered Scheduling
// ==========================================================================
float v2c[MAX_CHECK_DEGREE];
const float alpha = 0.75f; // Normalization factor
for (int iter = 0; iter < LDPC_MAX_ITER; iter++) {
// Process each check node (layer)
for (int c = 0; c < M_BITS; c++) {
int deg = check_degree[c];
// Step 1: Compute variable-to-check messages
for (int i = 0; i < deg; i++) {
int v = check_to_var[c][i];
v2c[i] = var_llr[v] - c2v[c][i];
}
// Step 2: Compute check-to-variable messages using min-sum
for (int i = 0; i < deg; i++) {
float sign_prod = 1.0f;
float min1 = LLR_MAX, min2 = LLR_MAX;
for (int j = 0; j < deg; j++) {
if (j == i) continue;
float val = v2c[j];
if (val < 0) sign_prod = -sign_prod;
float absval = fabsf(val);
if (absval < min1) {
min2 = min1;
min1 = absval;
} else if (absval < min2) {
min2 = absval;
}
}
// Normalized min-sum message
float msg_mag = alpha * min1;
float new_c2v = sign_prod * msg_mag;
// Update variable LLR immediately (layered approach)
int v = check_to_var[c][i];
var_llr[v] = clamp_llr(var_llr[v] - c2v[c][i] + new_c2v);
c2v[c][i] = new_c2v;
}
}
// Make hard decisions
for (int v = 0; v < N_BITS; v++) {
set_bit(codeword, v, var_llr[v] < 0 ? 1 : 0);
}
// Check if valid codeword
if (ldpc_p_check_syndrome(codeword)) {
memcpy(data, codeword, data_len);
return iter + 1;
}
// Adaptive restart at iteration milestones
if (iter == 25 || iter == 50 || iter == 75) {
float new_mag = 4.0f - (iter / 25) * 0.5f;
for (int v = 0; v < N_BITS; v++) {
int bit = get_bit(codeword, v);
var_llr[v] = bit ? -new_mag : new_mag;
}
for (int c = 0; c < M_BITS; c++) {
for (int i = 0; i < check_degree[c]; i++) {
c2v[c][i] = 0.0f;
}
}
}
}
// Failed to converge
memcpy(data, codeword, data_len);
return -1;
}
// =============================================================================
// Block-level operations
// =============================================================================
size_t ldpc_p_encode_blocks(const uint8_t *data, size_t data_len, uint8_t *output) {
if (!ldpc_p_initialized) ldpc_p_init();
size_t output_len = 0;
size_t remaining = data_len;
const uint8_t *src = data;
uint8_t *dst = output;
while (remaining > 0) {
size_t block_data = (remaining > LDPC_P_DATA_SIZE) ? LDPC_P_DATA_SIZE : remaining;
ldpc_p_encode(src, block_data, dst);
src += block_data;
dst += LDPC_P_BLOCK_SIZE;
output_len += LDPC_P_BLOCK_SIZE;
remaining -= block_data;
}
return output_len;
}
int ldpc_p_decode_blocks(uint8_t *data, size_t total_len, uint8_t *output, size_t output_len) {
if (!ldpc_p_initialized) ldpc_p_init();
int total_iterations = 0;
size_t remaining_output = output_len;
uint8_t *src = data;
uint8_t *dst = output;
while (total_len >= LDPC_P_BLOCK_SIZE && remaining_output > 0) {
size_t bytes_to_copy = (remaining_output > LDPC_P_DATA_SIZE) ? LDPC_P_DATA_SIZE : remaining_output;
int result = ldpc_p_decode(src, LDPC_P_DATA_SIZE);
if (result < 0) {
return -1;
}
total_iterations += result;
memcpy(dst, src, bytes_to_copy);
src += LDPC_P_BLOCK_SIZE;
dst += bytes_to_copy;
total_len -= LDPC_P_BLOCK_SIZE;
remaining_output -= bytes_to_copy;
}
return total_iterations;
}

97
video_encoder/lib/libfec/ldpc_payload.h Normal file
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@@ -0,0 +1,97 @@
/**
* LDPC(255,223) Codec for TAV-DT Payloads
*
* Alternative to RS(255,223) with same rate (~0.875):
* - Block size: 255 bytes (223 data + 32 parity)
* - Uses quasi-cyclic LDPC structure for efficiency
* - Soft-decision belief propagation decoder
*
* Designed as drop-in replacement for RS(255,223):
* - Same input/output sizes
* - Same API style
* - Different error correction characteristics:
* - LDPC: Better at high BER (>1e-3), gradual degradation
* - RS: Better at low BER, hard threshold at 16 byte errors
*
* Created by CuriousTorvald and Claude on 2025-12-15.
*/
#ifndef LDPC_PAYLOAD_H
#define LDPC_PAYLOAD_H
#include <stdint.h>
#include <stddef.h>
// LDPC(255,223) parameters - matches RS(255,223) for drop-in replacement
#define LDPC_P_BLOCK_SIZE 255 // Total codeword size (bytes)
#define LDPC_P_DATA_SIZE 223 // Data bytes per block
#define LDPC_P_PARITY_SIZE 32 // Parity bytes per block
// Decoder parameters
#define LDPC_P_MAX_ITERATIONS 30 // Maximum BP iterations
#define LDPC_P_EARLY_TERM 1 // Enable early termination on valid codeword
/**
* Initialize LDPC(255,223) codec.
* Must be called once before using encode/decode functions.
* Thread-safe: uses static initialization.
*/
void ldpc_p_init(void);
/**
* Encode data block with LDPC(255,223).
*
* @param data Input data (up to LDPC_P_DATA_SIZE bytes)
* @param data_len Length of input data (1 to LDPC_P_DATA_SIZE)
* @param output Output buffer (must hold data_len + LDPC_P_PARITY_SIZE bytes)
* Format: [data][parity]
* @return Total output length (data_len + LDPC_P_PARITY_SIZE)
*
* Note: For data shorter than LDPC_P_DATA_SIZE, the encoder pads with zeros
* internally but only outputs actual data + parity.
*/
size_t ldpc_p_encode(const uint8_t *data, size_t data_len, uint8_t *output);
/**
* Decode and correct LDPC(255,223) encoded block.
*
* @param data Buffer containing [data][parity] (modified in-place)
* @param data_len Length of data portion (1 to LDPC_P_DATA_SIZE)
* @return Number of iterations used (1-30), or -1 if uncorrectable
*
* On success, data buffer contains corrected data.
* On failure, data buffer contents are undefined.
*/
int ldpc_p_decode(uint8_t *data, size_t data_len);
/**
* Encode data with automatic block splitting.
* For data larger than LDPC_P_DATA_SIZE, splits into multiple blocks.
*
* @param data Input data
* @param data_len Length of input data
* @param output Output buffer (must hold ceil(data_len/223) * 255 bytes)
* @return Total output length
*/
size_t ldpc_p_encode_blocks(const uint8_t *data, size_t data_len, uint8_t *output);
/**
* Decode data with automatic block splitting.
*
* @param data Buffer containing LDPC-encoded blocks (modified in-place)
* @param total_len Total length of encoded data (multiple of LDPC_P_BLOCK_SIZE)
* @param output Output buffer for decoded data
* @param output_len Expected length of decoded data
* @return Total iterations across all blocks, or -1 if any block failed
*/
int ldpc_p_decode_blocks(uint8_t *data, size_t total_len, uint8_t *output, size_t output_len);
/**
* Check if codeword is valid (syndrome check).
*
* @param codeword Full codeword (LDPC_P_BLOCK_SIZE bytes)
* @return 1 if valid (zero syndrome), 0 if errors detected
*/
int ldpc_p_check_syndrome(const uint8_t *codeword);
#endif // LDPC_PAYLOAD_H

63
video_encoder/src/decoder_tav_dt.c
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@@ -36,6 +36,11 @@
#include "decoder_tad.h"
#include "reed_solomon.h"
#include "ldpc.h"
#include "ldpc_payload.h"
// FEC mode for payloads (must match encoder setting)
#define FEC_MODE_RS 0 // Reed-Solomon (255,223) - default
#define FEC_MODE_LDPC 1 // LDPC (255,223) - experimental
// =============================================================================
// Constants
@@ -187,6 +192,7 @@ typedef struct {
// Options
int verbose;
int dump_mode; // Just dump packets, don't decode
int fec_mode; // FEC_MODE_RS or FEC_MODE_LDPC (must match encoder)
// Multithreading
int num_threads;
@@ -226,11 +232,27 @@ static void print_usage(const char *program) {
printf("\nOptions:\n");
printf(" -t, --threads N Number of decoder threads (default: min(8, available CPUs))\n");
printf(" 0 or 1 = single-threaded, 2-16 = multithreaded\n");
printf(" --ldpc-payload Use LDPC(255,223) instead of RS(255,223) for payloads\n");
printf(" (must match encoder setting)\n");
printf(" --dump Dump packet info without decoding\n");
printf(" -v, --verbose Verbose output\n");
printf(" --help Show this help\n");
}
// =============================================================================
// FEC Block Decoding (RS or LDPC based on mode)
// =============================================================================
static int decode_fec_blocks(uint8_t *data, size_t total_len, uint8_t *output, size_t output_len, int fec_mode) {
if (fec_mode == FEC_MODE_LDPC) {
// Use LDPC(255,223) decoding
return ldpc_p_decode_blocks(data, total_len, output, output_len);
} else {
// Use RS(255,223) decoding (default)
return rs_decode_blocks(data, total_len, output, output_len);
}
}
static void generate_random_filename(char *filename, size_t size) {
static int seeded = 0;
if (!seeded) {
@@ -763,17 +785,17 @@ static int decode_audio_subpacket(dt_decoder_t *dec, const uint8_t *data, size_t
return -1;
}
int rs_result = rs_decode_blocks(rs_data, rs_total, decoded_payload, compressed_size);
if (rs_result < 0) {
int fec_result = decode_fec_blocks(rs_data, rs_total, decoded_payload, compressed_size, dec->fec_mode);
if (fec_result < 0) {
if (dec->verbose) {
fprintf(stderr, "Warning: RS decode failed for audio - UNRECOVERABLE\n");
fprintf(stderr, "Warning: FEC decode failed for audio - UNRECOVERABLE\n");
}
free(rs_data);
free(decoded_payload);
*consumed = offset + rs_total;
return -1; // Unrecoverable - RS failed
} else if (rs_result > 0) {
dec->fec_corrections += rs_result;
return -1; // Unrecoverable - FEC failed
} else if (fec_result > 0) {
dec->fec_corrections += fec_result;
}
// decoded_payload already contains the full TAD chunk format:
@@ -876,17 +898,17 @@ static int decode_video_subpacket_mt(dt_decoder_t *dec, const uint8_t *data, siz
return -1;
}
int rs_result = rs_decode_blocks(rs_data, rs_total, decoded_payload, compressed_size);
if (rs_result < 0) {
int fec_result = decode_fec_blocks(rs_data, rs_total, decoded_payload, compressed_size, dec->fec_mode);
if (fec_result < 0) {
if (dec->verbose) {
fprintf(stderr, "Warning: RS decode failed for video (MT) - UNRECOVERABLE\n");
fprintf(stderr, "Warning: FEC decode failed for video (MT) - UNRECOVERABLE\n");
}
free(rs_data);
free(decoded_payload);
*consumed = offset + rs_total;
return -1; // Unrecoverable - RS failed
} else if (rs_result > 0) {
dec->fec_corrections += rs_result;
return -1; // Unrecoverable - FEC failed
} else if (fec_result > 0) {
dec->fec_corrections += fec_result;
}
free(rs_data);
@@ -1050,17 +1072,17 @@ static int decode_video_subpacket(dt_decoder_t *dec, const uint8_t *data, size_t
return -1;
}
int rs_result = rs_decode_blocks(rs_data, rs_total, decoded_payload, compressed_size);
if (rs_result < 0) {
int fec_result = decode_fec_blocks(rs_data, rs_total, decoded_payload, compressed_size, dec->fec_mode);
if (fec_result < 0) {
if (dec->verbose) {
fprintf(stderr, "Warning: RS decode failed for video - UNRECOVERABLE\n");
fprintf(stderr, "Warning: FEC decode failed for video - UNRECOVERABLE\n");
}
free(rs_data);
free(decoded_payload);
*consumed = offset + rs_total;
return -1; // Unrecoverable - RS failed
} else if (rs_result > 0) {
dec->fec_corrections += rs_result;
return -1; // Unrecoverable - FEC failed
} else if (fec_result > 0) {
dec->fec_corrections += fec_result;
}
// Initialize video decoder if needed
@@ -1680,11 +1702,13 @@ int main(int argc, char **argv) {
// Initialize FEC libraries
rs_init();
ldpc_init();
ldpc_p_init(); // LDPC payload codec
static struct option long_options[] = {
{"input", required_argument, 0, 'i'},
{"output", required_argument, 0, 'o'},
{"threads", required_argument, 0, 't'},
{"ldpc-payload", no_argument, 0, 'D'},
{"dump", no_argument, 0, 'd'},
{"verbose", no_argument, 0, 'v'},
{"help", no_argument, 0, 'h'},
@@ -1711,6 +1735,9 @@ int main(int argc, char **argv) {
if (dec.num_threads > MAX_DECODE_THREADS) dec.num_threads = MAX_DECODE_THREADS;
break;
}
case 'D':
dec.fec_mode = FEC_MODE_LDPC;
break;
case 'd':
dec.dump_mode = 1;
break;

30
video_encoder/src/encoder_tav_dt.c
View File

@@ -36,6 +36,11 @@
#include "encoder_tad.h"
#include "reed_solomon.h"
#include "ldpc.h"
#include "ldpc_payload.h"
// FEC mode for payloads (stored in flags byte bit 2)
#define FEC_MODE_RS 0 // Reed-Solomon (255,223) - default
#define FEC_MODE_LDPC 1 // LDPC (255,223) - experimental
// =============================================================================
// Constants
@@ -197,6 +202,7 @@ typedef struct {
// Options
int verbose;
int encode_limit;
int fec_mode; // FEC_MODE_RS or FEC_MODE_LDPC for payloads
// Multithreading
int num_threads; // 0 = single-threaded, 1+ = num worker threads
@@ -226,6 +232,8 @@ static void print_usage(const char *program) {
printf(" --ntsc Force NTSC format (720x480, default)\n");
printf(" --pal Force PAL format (720x576)\n");
printf(" --interlaced Interlaced output\n");
printf(" --ldpc-payload Use LDPC(255,223) instead of RS(255,223) for payloads\n");
printf(" (experimental: better at high error rates)\n");
printf(" --encode-limit N Encode only N frames (for testing)\n");
printf(" -t, --threads N Parallel encoding threads (default: min(8, available CPUs))\n");
printf(" 0 or 1 = single-threaded, 2-16 = multithreaded\n");
@@ -234,10 +242,15 @@ static void print_usage(const char *program) {
}
// =============================================================================
// RS Block Encoding
// FEC Block Encoding (RS or LDPC based on mode)
// =============================================================================
static size_t encode_rs_blocks(const uint8_t *data, size_t data_len, uint8_t *output) {
static size_t encode_fec_blocks(const uint8_t *data, size_t data_len, uint8_t *output, int fec_mode) {
if (fec_mode == FEC_MODE_LDPC) {
// Use LDPC(255,223) encoding
return ldpc_p_encode_blocks(data, data_len, output);
} else {
// Use RS(255,223) encoding (default)
size_t output_len = 0;
size_t remaining = data_len;
const uint8_t *src = data;
@@ -260,6 +273,7 @@ static size_t encode_rs_blocks(const uint8_t *data, size_t data_len, uint8_t *ou
return output_len;
}
}
// =============================================================================
// Packet Writing
@@ -355,12 +369,12 @@ static int write_packet(dt_encoder_t *enc, uint64_t timecode_ns,
uint8_t ldpc_tav_header[DT_TAV_HEADER_SIZE * 2];
ldpc_encode(tav_header, DT_TAV_HEADER_SIZE, ldpc_tav_header);
// RS encode payloads
// FEC encode payloads (RS or LDPC based on mode)
uint8_t *tad_rs_data = malloc(tad_rs_size);
uint8_t *tav_rs_data = malloc(tav_rs_size);
encode_rs_blocks(tad_data, tad_size, tad_rs_data);
encode_rs_blocks(tav_data, tav_size, tav_rs_data);
encode_fec_blocks(tad_data, tad_size, tad_rs_data, enc->fec_mode);
encode_fec_blocks(tav_data, tav_size, tav_rs_data, enc->fec_mode);
// Write everything
fwrite(ldpc_header, 1, DT_MAIN_HEADER_SIZE * 2, enc->output_fp);
@@ -1268,6 +1282,7 @@ int main(int argc, char **argv) {
// Initialize FEC libraries
rs_init();
ldpc_init();
ldpc_p_init(); // LDPC payload codec
static struct option long_options[] = {
{"input", required_argument, 0, 'i'},
@@ -1277,6 +1292,7 @@ int main(int argc, char **argv) {
{"ntsc", no_argument, 0, 'N'},
{"pal", no_argument, 0, 'P'},
{"interlaced", no_argument, 0, 'I'},
{"ldpc-payload", no_argument, 0, 'D'},
{"encode-limit", required_argument, 0, 'L'},
{"verbose", no_argument, 0, 'v'},
{"help", no_argument, 0, 'h'},
@@ -1319,6 +1335,9 @@ int main(int argc, char **argv) {
case 'I':
enc.is_interlaced = 1;
break;
case 'D':
enc.fec_mode = FEC_MODE_LDPC;
break;
case 'L':
enc.encode_limit = atoi(optarg);
break;
@@ -1366,6 +1385,7 @@ int main(int argc, char **argv) {
printf(" Framerate: %d/%d\n", enc.fps_num, enc.fps_den);
printf(" Quality: %d\n", enc.quality_index);
printf(" GOP size: %d\n", DT_GOP_SIZE);
printf(" Payload FEC: %s\n", enc.fec_mode == FEC_MODE_LDPC ? "LDPC(255,223)" : "RS(255,223)");
printf(" Threads: %d%s\n", enc.num_threads > 0 ? enc.num_threads : 1,
enc.num_threads > 0 ? " (multithreaded)" : " (single-threaded)");
printf(" Header sizes: main=%dB tad=%dB tav=%dB (after LDPC)\n",