sdrangel/plugins/channelrx/demoddatv/ldpctool/ldpc_tool.cpp

/*
LDPC testbench
Copyright 2018 Ahmet Inan <xdsopl@gmail.com>

Transformed into external decoder for third-party applications
Copyright 2019 <pabr@pabr.org>
*/

#include <stdlib.h>
#include <unistd.h>
#include <iostream>
#include <iomanip>
#include <random>
#include <cmath>
#include <cassert>
#include <chrono>
#include <cstring>
#include <algorithm>
#include <functional>
#include "testbench.h"
#include "algorithms.h"

#if 0
#include "flooding_decoder.h"
static const int DEFAULT_TRIALS = 50;
#else
#include "layered_decoder.h"
static const int DEFAULT_TRIALS = 25;
#endif

ldpctool::LDPCInterface *create_ldpc(char *standard, char prefix, int number);

void fail(const char *msg)
{
	std::cerr << "** plugin: " << msg << std::endl;
	exit(1);
}

void fatal(const char *msg)
{
	fprintf(stderr, "** plugin: ");
	perror(msg);
	exit(1);
}

void usage(const char *name, FILE *f, int c, const char *info = NULL)
{
	fprintf(f, "Usage: %s [--standard DVB-S2] --modcod INT [--trials INT] [--shortframes]  < FECFRAMES.int8  > FECFRAMES.int8\n", name);
	if (info)
		fprintf(f, "** Error while processing '%s'\n", info);
	exit(c);
}

int main(int argc, char **argv)
{
	const char *standard = "DVB-S2";
	int modcod = -1;
	int max_trials = DEFAULT_TRIALS;
	bool shortframes = false;

	for (int i = 1; i < argc; ++i)
	{
		if (!strcmp(argv[i], "--standard") && i + 1 < argc)
			standard = argv[++i];
		else if (!strcmp(argv[i], "--modcod") && i + 1 < argc)
			modcod = atoi(argv[++i]);
		else if (!strcmp(argv[i], "--trials") && i + 1 < argc)
			max_trials = atoi(argv[++i]);
		else if (!strcmp(argv[i], "--shortframes"))
			shortframes = true;
		else if (!strcmp(argv[i], "-h"))
			usage(argv[0], stdout, 0);
		else
			usage(argv[0], stderr, 1, argv[i]);
	}

	if (strcmp(standard, "DVB-S2"))
		fail("Only DVB-S2 is supported.");

	if (modcod < 0 || modcod > 31)
		usage(argv[0], stderr, 1);

	typedef ldpctool::NormalUpdate<ldpctool::simd_type> update_type;
	//typedef SelfCorrectedUpdate<simd_type> update_type;

	//typedef MinSumAlgorithm<simd_type, update_type> algorithm_type;
	//typedef OffsetMinSumAlgorithm<simd_type, update_type, FACTOR> algorithm_type;
	typedef ldpctool::MinSumCAlgorithm<ldpctool::simd_type, update_type, ldpctool::FACTOR> algorithm_type;
	//typedef LogDomainSPA<simd_type, update_type> algorithm_type;
	//typedef LambdaMinAlgorithm<simd_type, update_type, 3> algorithm_type;
	//typedef SumProductAlgorithm<simd_type, update_type> algorithm_type;

	ldpctool::LDPCDecoder<ldpctool::simd_type, algorithm_type> decode;

	// DVB-S2 MODCOD definitions
	static const char *mc_tabnames[2][32] = { // [shortframes][modcod]
											 {// Normal frames
											  0, "B1", "B2", "B3", "B4", "B5", "B6", "B7",
											  "B8", "B9", "B10", "B11", "B5", "B6", "B7", "B9",
											  "B10", "B11", "B6", "B7", "B8", "B9", "B10", "B11",
											  "B7", "B8", "B8", "B10", "B11", 0, 0, 0},
											 {// Short frames
											  0, "C1", "C2", "C3", "C4", "C5", "C6", "C7",
											  "C8", "C9", "C10", 0, "C5", "C6", "C7", "C9",
											  "C10", 0, "C6", "C7", "C8", "C9", "C10", 0,
											  "C7", "C8", "C8", "C10", 0, 0, 0, 0}};

	const char *tabname = mc_tabnames[shortframes][modcod];
	if (!tabname)
		fail("unsupported modcod");

	ldpctool::LDPCInterface *ldpc = create_ldpc((char *)"S2", tabname[0], atoi(tabname + 1));

	if (!ldpc)
	{
		std::cerr << "no such table!" << std::endl;
		return -1;
	}

	const int CODE_LEN = ldpc->code_len();
	const int DATA_LEN = ldpc->data_len();

	decode.init(ldpc);

	int BLOCKS = 32;
	ldpctool::code_type *code = new ldpctool::code_type[BLOCKS * CODE_LEN];
	void *aligned_buffer = aligned_alloc(sizeof(ldpctool::simd_type), sizeof(ldpctool::simd_type) * CODE_LEN);
	ldpctool::simd_type *simd = reinterpret_cast<ldpctool::simd_type *>(aligned_buffer);

	// Expect LLR values in int8_t format.
	if (sizeof(ldpctool::code_type) != 1)
		fail("Bug: Unsupported code_type");

	while (true)
	{
		ssize_t iosize = BLOCKS * CODE_LEN * sizeof(*code);

		for (ssize_t pos = 0; pos < iosize;)
		{
			int nr = read(0, code + pos, iosize - pos);

			if (!nr)
				exit(0);

			if (nr < 0)
				fatal("read");

			pos += nr;
		}

		int iterations = 0;
		int num_decodes = 0;

		for (int j = 0; j < BLOCKS; j += ldpctool::SIMD_WIDTH)
		{
			int blocks = j + ldpctool::SIMD_WIDTH > BLOCKS ? BLOCKS - j : ldpctool::SIMD_WIDTH;

			for (int n = 0; n < blocks; ++n)
				for (int i = 0; i < CODE_LEN; ++i)
					reinterpret_cast<ldpctool::code_type *>(simd + i)[n] = code[(j + n) * CODE_LEN + i];

			int trials = max_trials;
			int count = decode(simd, simd + DATA_LEN, trials, blocks);
			++num_decodes;

			for (int n = 0; n < blocks; ++n)
				for (int i = 0; i < CODE_LEN; ++i)
					code[(j + n) * CODE_LEN + i] = reinterpret_cast<ldpctool::code_type *>(simd + i)[n];

			if (count < 0) {
				iterations += blocks * trials;
				// std::cerr << "decoder failed at converging to a code word in " << trials << " trials" << std::endl;
			} else {
				iterations += blocks * (trials - count);
			}
		}

		for (int i = 0; i < BLOCKS * CODE_LEN; ++i)
			assert(!std::isnan(code[i]));

		for (ssize_t pos = 0; pos < iosize;)
		{
			ssize_t nw = write(1, code + pos, iosize - pos);

			if (!nw)
				exit(0);

			if (nw < 0)
				fatal("write");

			pos += nw;
		}
	} // main loop

	delete ldpc;

	free(aligned_buffer);
	delete[] code;

	return 0;
}