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SSDV/ssdv.c

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/* SSDV - Slow Scan Digital Video */
/*=======================================================================*/
/* Copyright 2011-2016 Philip Heron <phil@sanslogic.co.uk> */
/* */
/* This program is free software: you can redistribute it and/or modify */
/* it under the terms of the GNU General Public License as published by */
/* the Free Software Foundation, either version 3 of the License, or */
/* (at your option) any later version. */
/* */
/* This program is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
/* GNU General Public License for more details. */
/* */
/* You should have received a copy of the GNU General Public License */
/* along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include "ssdv.h"
#include "rs8.h"
/* Recognised JPEG markers */
enum {
J_TEM = 0xFF01,
J_SOF0 = 0xFFC0, J_SOF1, J_SOF2, J_SOF3, J_DHT, J_SOF5, J_SOF6, J_SOF7,
J_JPG, J_SOF9, J_SOF10, J_SOF11, J_DAC, J_SOF13, J_SOF14, J_SOF15,
J_RST0, J_RST1, J_RST2, J_RST3, J_RST4, J_RST5, J_RST6, J_RST7,
J_SOI, J_EOI, J_SOS, J_DQT, J_DNL, J_DRI, J_DHP, J_EXP,
J_APP0, J_APP1, J_APP2, J_APP3, J_APP4, J_APP5, J_APP6, J_APP7,
J_APP8, J_APP9, J_APP10, J_APP11, J_APP12, J_APP13, J_APP14, J_APP15,
J_JPG0, J_JPG1, J_JPG2, J_JPG3, J_JPG4, J_JPG5, J_JPG6, J_SOF48,
J_LSE, J_JPG9, J_JPG10, J_JPG11, J_JPG12, J_JPG13, J_COM,
} jpeg_marker_t;
/* APP0 header data */
static uint8_t const app0[14] = {
0x4A,0x46,0x49,0x46,0x00,0x01,0x01,0x01,0x00,0x48,0x00,0x48,0x00,0x00,
};
/* SOS header data */
static uint8_t const sos[10] = {
0x03,0x01,0x00,0x02,0x11,0x03,0x11,0x00,0x3F,0x00,
};
/* Quantisation table scaling factors for each quality level 0-7 */
static uint16_t const dqt_scales[8] = {
5000, 357, 172, 116, 100, 58, 28, 0
};
/* Quantisation tables */
static uint8_t const std_dqt0[65] = {
0x00,0x10,0x0C,0x0C,0x0E,0x0C,0x0A,0x10,0x0E,0x0E,0x0E,0x12,0x12,0x10,0x14,0x18,
0x28,0x1A,0x18,0x16,0x16,0x18,0x32,0x24,0x26,0x1E,0x28,0x3A,0x34,0x3E,0x3C,0x3A,
0x34,0x38,0x38,0x40,0x48,0x5C,0x4E,0x40,0x44,0x58,0x46,0x38,0x38,0x50,0x6E,0x52,
0x58,0x60,0x62,0x68,0x68,0x68,0x3E,0x4E,0x72,0x7A,0x70,0x64,0x78,0x5C,0x66,0x68,
0x64,
};
static uint8_t const std_dqt1[65] = {
0x01,0x12,0x12,0x12,0x16,0x16,0x16,0x30,0x1A,0x1A,0x30,0x64,0x42,0x38,0x42,0x64,
0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,
0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,
0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64,
0x64,
};
/* Standard Huffman tables */
static uint8_t const std_dht00[29] = {
0x00,0x00,0x01,0x05,0x01,0x01,0x01,0x01,0x01,0x01,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,
};
static uint8_t const std_dht01[29] = {
0x01,0x00,0x03,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x00,0x00,0x00,0x00,
0x00,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,
};
static uint8_t const std_dht10[179] = {
0x10,0x00,0x02,0x01,0x03,0x03,0x02,0x04,0x03,0x05,0x05,0x04,0x04,0x00,0x00,0x01,
0x7D,0x01,0x02,0x03,0x00,0x04,0x11,0x05,0x12,0x21,0x31,0x41,0x06,0x13,0x51,0x61,
0x07,0x22,0x71,0x14,0x32,0x81,0x91,0xA1,0x08,0x23,0x42,0xB1,0xC1,0x15,0x52,0xD1,
0xF0,0x24,0x33,0x62,0x72,0x82,0x09,0x0A,0x16,0x17,0x18,0x19,0x1A,0x25,0x26,0x27,
0x28,0x29,0x2A,0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x43,0x44,0x45,0x46,0x47,0x48,
0x49,0x4A,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0x63,0x64,0x65,0x66,0x67,0x68,
0x69,0x6A,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0x83,0x84,0x85,0x86,0x87,0x88,
0x89,0x8A,0x92,0x93,0x94,0x95,0x96,0x97,0x98,0x99,0x9A,0xA2,0xA3,0xA4,0xA5,0xA6,
0xA7,0xA8,0xA9,0xAA,0xB2,0xB3,0xB4,0xB5,0xB6,0xB7,0xB8,0xB9,0xBA,0xC2,0xC3,0xC4,
0xC5,0xC6,0xC7,0xC8,0xC9,0xCA,0xD2,0xD3,0xD4,0xD5,0xD6,0xD7,0xD8,0xD9,0xDA,0xE1,
0xE2,0xE3,0xE4,0xE5,0xE6,0xE7,0xE8,0xE9,0xEA,0xF1,0xF2,0xF3,0xF4,0xF5,0xF6,0xF7,
0xF8,0xF9,0xFA,
};
static uint8_t const std_dht11[179] = {
0x11,0x00,0x02,0x01,0x02,0x04,0x04,0x03,0x04,0x07,0x05,0x04,0x04,0x00,0x01,0x02,
0x77,0x00,0x01,0x02,0x03,0x11,0x04,0x05,0x21,0x31,0x06,0x12,0x41,0x51,0x07,0x61,
0x71,0x13,0x22,0x32,0x81,0x08,0x14,0x42,0x91,0xA1,0xB1,0xC1,0x09,0x23,0x33,0x52,
0xF0,0x15,0x62,0x72,0xD1,0x0A,0x16,0x24,0x34,0xE1,0x25,0xF1,0x17,0x18,0x19,0x1A,
0x26,0x27,0x28,0x29,0x2A,0x35,0x36,0x37,0x38,0x39,0x3A,0x43,0x44,0x45,0x46,0x47,
0x48,0x49,0x4A,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0x63,0x64,0x65,0x66,0x67,
0x68,0x69,0x6A,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0x82,0x83,0x84,0x85,0x86,
0x87,0x88,0x89,0x8A,0x92,0x93,0x94,0x95,0x96,0x97,0x98,0x99,0x9A,0xA2,0xA3,0xA4,
0xA5,0xA6,0xA7,0xA8,0xA9,0xAA,0xB2,0xB3,0xB4,0xB5,0xB6,0xB7,0xB8,0xB9,0xBA,0xC2,
0xC3,0xC4,0xC5,0xC6,0xC7,0xC8,0xC9,0xCA,0xD2,0xD3,0xD4,0xD5,0xD6,0xD7,0xD8,0xD9,
0xDA,0xE2,0xE3,0xE4,0xE5,0xE6,0xE7,0xE8,0xE9,0xEA,0xF2,0xF3,0xF4,0xF5,0xF6,0xF7,
0xF8,0xF9,0xFA,
};
/* Helper for returning the current DHT table */
#define SDHT (s->sdht[s->acpart ? 1 : 0][s->component ? 1 : 0])
#define DDHT (s->ddht[s->acpart ? 1 : 0][s->component ? 1 : 0])
/* Helpers for looking up the current DQT value */
#define SDQT (s->sdqt[s->component ? 1 : 0][1 + s->acpart])
#define DDQT (s->ddqt[s->component ? 1 : 0][1 + s->acpart])
/* Helpers for converting between DQT tables */
#define AADJ(i) (SDQT == DDQT ? (i) : irdiv(i, DDQT))
#define UADJ(i) (SDQT == DDQT ? (i) : (i * SDQT))
#define BADJ(i) (SDQT == DDQT ? (i) : irdiv(i * SDQT, DDQT))
/* Integer-only division with rounding */
static int irdiv(int i, int div)
{
i = i * 2 / div;
if(i & 1) i += (i > 0 ? 1 : -1);
return(i / 2);
}
/*
static char *strbits(uint32_t value, uint8_t bits)
{
static char s[33];
char *ss = s;
while(bits--) *(ss++) = value & 1 << bits ? '1' : '0';
*ss = '\0';
return(s);
}
*/
static void load_standard_dqt(uint8_t *dst, const uint8_t *table, uint8_t quality)
{
int i;
uint16_t scale_factor;
uint32_t temp;
/* Copy the table ID */
*dst++ = *table++;
/* Load the scaling factor */
if(quality > 7) quality = 7;
scale_factor = dqt_scales[quality];
/* Copy the remaining 64 coefficients, while applying the scaling factor */
for(i = 0; i < 64; i++)
{
temp = *table++;
temp = (temp * scale_factor + 50) / 100;
/* limit the values to the valid range */
if(temp == 0) temp = 1;
if(temp > 255) temp = 255;
*dst++ = temp;
}
}
static void *sload_standard_dqt(ssdv_t *s, const uint8_t *table, uint8_t quality)
{
uint8_t *r;
/* DQT is 65 bytes long, ensure there is space */
if(s->stbl_len + 65 > TBL_LEN + HBUFF_LEN) return(NULL);
r = &s->stbls[s->stbl_len];
load_standard_dqt(r, table, quality);
s->stbl_len += 65;
return(r);
}
static void *dload_standard_dqt(ssdv_t *s, const uint8_t *table, uint8_t quality)
{
uint8_t *r;
/* DQT is 65 bytes long, ensure there is space */
if(s->dtbl_len + 65 > TBL_LEN + HBUFF_LEN) return(NULL);
r = &s->dtbls[s->dtbl_len];
load_standard_dqt(r, table, quality);
s->dtbl_len += 65;
return(r);
}
static void *stblcpy(ssdv_t *s, const void *src, size_t n)
{
void *r;
if(s->stbl_len + n > TBL_LEN + HBUFF_LEN) return(NULL);
r = memcpy(&s->stbls[s->stbl_len], src, n);
s->stbl_len += n;
return(r);
}
static void *dtblcpy(ssdv_t *s, const void *src, size_t n)
{
void *r;
if(s->dtbl_len + n > TBL_LEN) return(NULL);
r = memcpy(&s->dtbls[s->dtbl_len], src, n);
s->dtbl_len += n;
return(r);
}
static uint32_t crc32(void *data, size_t length)
{
uint32_t crc, x;
uint8_t i, *d;
for(d = data, crc = 0xFFFFFFFF; length; length--)
{
x = (crc ^ *(d++)) & 0xFF;
for(i = 8; i > 0; i--)
{
if(x & 1) x = (x >> 1) ^ 0xEDB88320;
else x >>= 1;
}
crc = (crc >> 8) ^ x;
}
return(crc ^ 0xFFFFFFFF);
}
static uint32_t encode_callsign(char *callsign)
{
uint32_t x;
char *c;
/* Point c at the end of the callsign, maximum of 6 characters */
for(x = 0, c = callsign; x < SSDV_MAX_CALLSIGN && *c; x++, c++);
/* Encode it backwards */
x = 0;
for(c--; c >= callsign; c--)
{
x *= 40;
if(*c >= 'A' && *c <= 'Z') x += *c - 'A' + 14;
else if(*c >= 'a' && *c <= 'z') x += *c - 'a' + 14;
else if(*c >= '0' && *c <= '9') x += *c - '0' + 1;
}
return(x);
}
static char *decode_callsign(char *callsign, uint32_t code)
{
char *c, s;
*callsign = '\0';
/* Is callsign valid? */
if(code > 0xF423FFFF) return(callsign);
for(c = callsign; code; c++)
{
s = code % 40;
if(s == 0) *c = '-';
else if(s < 11) *c = '0' + s - 1;
else if(s < 14) *c = '-';
else *c = 'A' + s - 14;
code /= 40;
}
*c = '\0';
return(callsign);
}
static inline char jpeg_dht_lookup(ssdv_t *s, uint8_t *symbol, uint8_t *width)
{
uint16_t code = 0;
uint8_t cw, n;
uint8_t *dht, *ss;
/* Select the appropriate huffman table */
dht = SDHT;
ss = &dht[17];
for(cw = 1; cw <= 16; cw++)
{
/* Got enough bits? */
if(cw > s->worklen) return(SSDV_FEED_ME);
/* Compare against each code 'cw' bits wide */
for(n = dht[cw]; n > 0; n--)
{
if(s->workbits >> (s->worklen - cw) == code)
{
/* Found a match */
*symbol = *ss;
*width = cw;
return(SSDV_OK);
}
ss++; code++;
}
code <<= 1;
}
/* No match found - error */
return(SSDV_ERROR);
}
static inline char jpeg_dht_lookup_symbol(ssdv_t *s, uint8_t symbol, uint16_t *bits, uint8_t *width)
{
uint16_t code = 0;
uint8_t cw, n;
uint8_t *dht, *ss;
dht = DDHT;
ss = &dht[17];
for(cw = 1; cw <= 16; cw++)
{
for(n = dht[cw]; n > 0; n--)
{
if(*ss == symbol)
{
/* Found a match */
*bits = code;
*width = cw;
return(SSDV_OK);
}
ss++; code++;
}
code <<= 1;
}
/* No match found - error */
return(SSDV_ERROR);
}
static inline int jpeg_int(int bits, int width)
{
int b = (1 << width) - 1;
if(bits <= b >> 1) bits = -(bits ^ b);
return(bits);
}
static inline void jpeg_encode_int(int value, int *bits, uint8_t *width)
{
*bits = value;
/* Calculate the number of bits */
if(value < 0) value = -value;
for(*width = 0; value; value >>= 1) (*width)++;
/* Fix negative values */
if(*bits < 0) *bits = -*bits ^ ((1 << *width) - 1);
}
/*****************************************************************************/
static char ssdv_outbits(ssdv_t *s, uint16_t bits, uint8_t length)
{
uint8_t b;
if(length)
{
s->outbits <<= length;
s->outbits |= bits & ((1 << length) - 1);
s->outlen += length;
}
while(s->outlen >= 8 && s->out_len > 0)
{
b = s->outbits >> (s->outlen - 8);
/* Put the byte into the output buffer */
*(s->outp++) = b;
s->outlen -= 8;
s->out_len--;
/* Insert stuffing byte if needed */
if(s->out_stuff && b == 0xFF)
{
s->outbits &= (1 << s->outlen) - 1;
s->outlen += 8;
}
}
return(s->out_len ? SSDV_OK : SSDV_BUFFER_FULL);
}
static char ssdv_outbits_sync(ssdv_t *s)
{
uint8_t b = s->outlen % 8;
if(b) return(ssdv_outbits(s, 0xFF, 8 - b));
return(SSDV_OK);
}
static char ssdv_out_jpeg_int(ssdv_t *s, uint8_t rle, int value)
{
uint16_t huffbits = 0;
int intbits;
uint8_t hufflen = 0, intlen;
int r;
jpeg_encode_int(value, &intbits, &intlen);
r = jpeg_dht_lookup_symbol(s, (rle << 4) | (intlen & 0x0F), &huffbits, &hufflen);
if(r != SSDV_OK) fprintf(stderr, "jpeg_dht_lookup_symbol: %i (%i:%i)\n", r, value, rle);
ssdv_outbits(s, huffbits, hufflen);
if(intlen) ssdv_outbits(s, intbits, intlen);
return(SSDV_OK);
}
static char ssdv_process(ssdv_t *s)
{
if(s->state == S_HUFF)
{
uint8_t symbol, width;
int r;
if(s->mcupart == 0 && s->acpart == 0 && s->next_reset_mcu > s->reset_mcu)
{
s->reset_mcu = s->next_reset_mcu;
}
/* Lookup the code, return if error or not enough bits yet */
if((r = jpeg_dht_lookup(s, &symbol, &width)) != SSDV_OK)
{
return(r);
}
if(s->acpart == 0) /* DC */
{
if(symbol == 0x00)
{
/* No change in DC from last block */
if(s->reset_mcu == s->mcu_id && (s->mcupart == 0 || s->mcupart >= s->ycparts))
{
if(s->mode == S_ENCODING)
{
ssdv_out_jpeg_int(s, 0, s->adc[s->component]);
}
else
{
ssdv_out_jpeg_int(s, 0, 0 - s->dc[s->component]);
s->dc[s->component] = 0;
}
}
else ssdv_out_jpeg_int(s, 0, 0);
/* skip to the next AC part immediately */
s->acpart++;
}
else
{
/* DC value follows, 'symbol' bits wide */
s->state = S_INT;
s->needbits = symbol;
}
}
else /* AC */
{
s->acrle = 0;
if(symbol == 0x00)
{
/* EOB -- all remaining AC parts are zero */
ssdv_out_jpeg_int(s, 0, 0);
s->acpart = 64;
}
else if(symbol == 0xF0)
{
/* The next 16 AC parts are zero */
ssdv_out_jpeg_int(s, 15, 0);
s->acpart += 16;
}
else
{
/* Next bits are an integer value */
s->state = S_INT;
s->acrle = symbol >> 4;
s->acpart += s->acrle;
s->needbits = symbol & 0x0F;
}
}
/* Clear processed bits */
s->worklen -= width;
s->workbits &= (1 << s->worklen) - 1;
}
else if(s->state == S_INT)
{
int i;
/* Not enough bits yet? */
if(s->worklen < s->needbits) return(SSDV_FEED_ME);
/* Decode the integer */
i = jpeg_int(s->workbits >> (s->worklen - s->needbits), s->needbits);
if(s->acpart == 0) /* DC */
{
if(s->reset_mcu == s->mcu_id && (s->mcupart == 0 || s->mcupart >= s->ycparts))
{
if(s->mode == S_ENCODING)
{
/* Output absolute DC value */
s->dc[s->component] += UADJ(i);
s->adc[s->component] = AADJ(s->dc[s->component]);
ssdv_out_jpeg_int(s, 0, s->adc[s->component]);
}
else
{
/* Output relative DC value */
ssdv_out_jpeg_int(s, 0, i - s->dc[s->component]);
s->dc[s->component] = i;
}
}
else
{
if(s->mode == S_DECODING)
{
s->dc[s->component] += UADJ(i);
ssdv_out_jpeg_int(s, 0, i);
}
else
{
/* Output relative DC value */
s->dc[s->component] += UADJ(i);
/* Calculate closest adjusted DC value */
i = AADJ(s->dc[s->component]);
ssdv_out_jpeg_int(s, 0, i - s->adc[s->component]);
s->adc[s->component] = i;
}
}
}
else /* AC */
{
if((i = BADJ(i)))
{
s->accrle += s->acrle;
while(s->accrle >= 16)
{
ssdv_out_jpeg_int(s, 15, 0);
s->accrle -= 16;
}
ssdv_out_jpeg_int(s, s->accrle, i);
s->accrle = 0;
}
else
{
/* AC value got reduced to 0 in the DQT conversion */
if(s->acpart >= 63)
{
ssdv_out_jpeg_int(s, 0, 0);
s->accrle = 0;
}
else s->accrle += s->acrle + 1;
}
}
/* Next AC part to expect */
s->acpart++;
/* Next bits are a huffman code */
s->state = S_HUFF;
/* Clear processed bits */
s->worklen -= s->needbits;
s->workbits &= (1 << s->worklen) - 1;
}
if(s->acpart >= 64)
{
s->mcupart++;
if(s->greyscale && s->mcupart == s->ycparts)
{
/* For greyscale input images, pad the 2x1 MCUs with empty colour blocks */
for(; s->mcupart < s->ycparts + 2; s->mcupart++)
{
s->component = s->mcupart - s->ycparts + 1;
s->acpart = 0; ssdv_out_jpeg_int(s, 0, 0); /* DC */
s->acpart = 1; ssdv_out_jpeg_int(s, 0, 0); /* AC */
}
}
/* Reached the end of this MCU */
if(s->mcupart == s->ycparts + 2)
{
s->mcupart = 0;
s->mcu_id++;
/* Test for the end of image */
if(s->mcu_id >= s->mcu_count)
{
/* Flush any remaining bits */
ssdv_outbits_sync(s);
return(SSDV_EOI);
}
/* Set the packet MCU marker - encoder only */
if(s->mode == S_ENCODING && s->packet_mcu_id == 0xFFFF)
{
/* The first MCU of each packet should be byte aligned */
ssdv_outbits_sync(s);
s->next_reset_mcu = s->mcu_id;
s->packet_mcu_id = s->mcu_id;
s->packet_mcu_offset = s->pkt_size_payload - s->out_len + ((s->outlen + 7) / 8);
}
/* Test for a reset marker */
if(s->dri > 0 && s->mcu_id > 0 && s->mcu_id % s->dri == 0)
{
s->state = S_MARKER;
return(SSDV_FEED_ME);
}
}
if(s->mcupart < s->ycparts) s->component = 0;
else s->component = s->mcupart - s->ycparts + 1;
s->acpart = 0;
s->accrle = 0;
}
if(s->out_len == 0) return(SSDV_BUFFER_FULL);
return(SSDV_OK);
}
static void ssdv_set_packet_conf(ssdv_t *s)
{
/* Configure the payload size and CRC position */
switch(s->type)
{
case SSDV_TYPE_NORMAL:
s->pkt_size_payload = s->pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC - SSDV_PKT_SIZE_RSCODES;
s->pkt_size_crcdata = SSDV_PKT_SIZE_HEADER + s->pkt_size_payload - 1;
break;
case SSDV_TYPE_NOFEC:
s->pkt_size_payload = s->pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC;
s->pkt_size_crcdata = SSDV_PKT_SIZE_HEADER + s->pkt_size_payload - 1;
break;
}
}
/*****************************************************************************/
static void ssdv_memset_prng(uint8_t *s, size_t n)
{
/* A very simple PRNG for noise whitening */
uint8_t l = 0x00;
for(; n > 0; n--) *(s++) = (l = l * 245 + 45);
}
static char ssdv_have_marker(ssdv_t *s)
{
switch(s->marker)
{
case J_SOF0:
case J_SOS:
case J_DRI:
case J_DHT:
case J_DQT:
/* Copy the data before processing */
if(s->marker_len > TBL_LEN + HBUFF_LEN - s->stbl_len)
{
/* Not enough memory ... shouldn't happen! */
return(SSDV_ERROR);
}
s->marker_data = &s->stbls[s->stbl_len];
s->marker_data_len = 0;
s->state = S_MARKER_DATA;
break;
case J_SOF2:
/* Don't do progressive images! */
fprintf(stderr, "Error: Progressive images not supported\n");
return(SSDV_ERROR);
case J_EOI:
s->state = S_EOI;
break;
case J_RST0:
case J_RST1:
case J_RST2:
case J_RST3:
case J_RST4:
case J_RST5:
case J_RST6:
case J_RST7:
s->dc[0] = s->dc[1] = s->dc[2] = 0;
s->mcupart = s->acpart = s->component = 0;
s->acrle = s->accrle = 0;
s->workbits = s->worklen = 0;
s->state = S_HUFF;
break;
default:
/* Ignore other marks, skipping any associated data */
s->in_skip = s->marker_len;
s->state = S_MARKER;
break;
}
return(SSDV_OK);
}
static char ssdv_have_marker_data(ssdv_t *s)
{
uint8_t *d = s->marker_data;
ssize_t l = s->marker_len;
int i;
switch(s->marker)
{
case J_SOF0:
s->width = (d[3] << 8) | d[4];
s->height = (d[1] << 8) | d[2];
/* Display information about the image... */
fprintf(stderr, "Precision: %i\n", d[0]);
fprintf(stderr, "Resolution: %ix%i\n", s->width, s->height);
fprintf(stderr, "Components: %i\n", d[5]);
/* The image must have a precision of 8 */
if(d[0] != 8)
{
fprintf(stderr, "Error: The image must have a precision of 8\n");
return(SSDV_ERROR);
}
/* The image must have 1 or 3 components (Y'Cb'Cr) */
if(d[5] != 1 && d[5] != 3)
{
fprintf(stderr, "Error: The image must have 1 or 3 components\n");
return(SSDV_ERROR);
}
/* Maximum image is 4080x4080 */
if(s->width > 4080 || s->height > 4080)
{
fprintf(stderr, "Error: The image is too big. Maximum resolution is 4080x4080\n");
return(SSDV_ERROR);
}
/* The image dimensions must be a multiple of 16 */
if((s->width & 0x0F) || (s->height & 0x0F))
{
fprintf(stderr, "Error: The image dimensions must be a multiple of 16\n");
return(SSDV_ERROR);
}
/* TODO: Read in the quantisation table ID for each component */
// 01 22 00 02 11 01 03 11 01
for(i = 0; i < d[5]; i++)
{
uint8_t *dq = &d[i * 3 + 6];
fprintf(stderr, "DQT table for component %i: %02X, Sampling factor: %ix%i\n", dq[0], dq[2], dq[1] & 0x0F, dq[1] >> 4);
/* The first (Y) component must have a factor of 2x2,2x1,1x2 or 1x1 */
if(i == 0)
{
switch(dq[1])
{
case 0x22: s->mcu_mode = 0; s->ycparts = 4; break;
case 0x12: s->mcu_mode = 1; s->ycparts = 2; break;
case 0x21: s->mcu_mode = 2; s->ycparts = 2; break;
case 0x11: s->mcu_mode = 3; s->ycparts = 1; break;
default:
fprintf(stderr, "Error: Component 1 sampling factor is not supported\n");
return(SSDV_ERROR);
}
}
else if(i != 0 && dq[1] != 0x11)
{
fprintf(stderr, "Error: Component %i sampling factor must be 1x1\n", dq[0]);
return(SSDV_ERROR);
}
}
if(d[5] == 1)
{
/* Greyscale images are converted to 2x1 colour images */
s->greyscale = 1;
s->mcu_mode = 2;
s->ycparts = 2;
}
/* Calculate number of MCU blocks in this image */
switch(s->mcu_mode)
{
case 0: l = (s->width >> 4) * (s->height >> 4); break;
case 1: l = (s->width >> 4) * (s->height >> 3); break;
case 2: l = (s->width >> 3) * (s->height >> 4); break;
case 3: l = (s->width >> 3) * (s->height >> 3); break;
}
fprintf(stderr, "MCU blocks: %i\n", (int) l);
if(l > 0xFFFF)
{
fprintf(stderr, "Error: Maximum number of MCU blocks is 65535\n");
return(SSDV_ERROR);
}
s->mcu_count = l;
break;
case J_SOS:
fprintf(stderr, "Components: %i\n", d[0]);
/* The image must have 1 or 3 components (Y'Cb'Cr) */
if(d[0] != 1 && d[0] != 3)
{
fprintf(stderr, "Error: The image must have 1 or 3 components\n");
return(SSDV_ERROR);
}
for(i = 0; i < d[0]; i++)
{
uint8_t *dh = &d[i * 2 + 1];
fprintf(stderr, "Component %i DHT: %02X\n", dh[0], dh[1]);
}
/* Do I need to look at the last three bytes of the SOS data? */
/* 00 3F 00 */
/* Verify all of the DQT and DHT tables where loaded */
if(!s->sdqt[0] || (d[0] > 1 && !s->sdqt[1]))
{
fprintf(stderr, "Error: The image is missing one or more DQT tables\n");
return(SSDV_ERROR);
}
if(!s->sdht[0][0] || (d[0] > 1 && !s->sdht[0][1]) ||
!s->sdht[1][0] || (d[0] > 1 && !s->sdht[1][1]))
{
fprintf(stderr, "Error: The image is missing one or more DHT tables\n");
return(SSDV_ERROR);
}
/* The SOS data is followed by the image data */
s->state = S_HUFF;
return(SSDV_OK);
case J_DHT:
s->stbl_len += l;
while(l > 0)
{
int i, j;
switch(d[0])
{
case 0x00: s->sdht[0][0] = d; break;
case 0x01: s->sdht[0][1] = d; break;
case 0x10: s->sdht[1][0] = d; break;
case 0x11: s->sdht[1][1] = d; break;
}
/* Skip to the next DHT table */
for(j = 17, i = 1; i <= 16; i++)
j += d[i];
l -= j;
if (l < 0)
{
fprintf(stderr, "The image has an invalid marker length\n");
return(SSDV_ERROR);
}
d += j;
}
break;
case J_DQT:
s->stbl_len += l;
while(l > 0)
{
switch(d[0])
{
case 0x00: s->sdqt[0] = d; break;
case 0x01: s->sdqt[1] = d; break;
}
/* Skip to the next one, if present */
l -= 65;
if (l < 0)
{
fprintf(stderr, "The image has an invalid marker length\n");
return(SSDV_ERROR);
}
d += 65;
}
break;
case J_DRI:
s->dri = (d[0] << 8) + d[1];
fprintf(stderr, "Reset interval: %i blocks\n", s->dri);
break;
}
s->state = S_MARKER;
return(SSDV_OK);
}
char ssdv_enc_init(ssdv_t *s, uint8_t type, char *callsign, uint8_t image_id, int8_t quality, int pkt_size)
{
/* Limit the quality level */
if(quality < 0) quality = 0;
if(quality > 7) quality = 7;
/* Limit the packet length */
if(pkt_size > SSDV_PKT_SIZE ||
pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC - (type == SSDV_TYPE_NORMAL ? SSDV_PKT_SIZE_RSCODES : 0) < 2)
{
fprintf(stderr, "Invalid SSDV packet length\n");
return(SSDV_ERROR);
}
memset(s, 0, sizeof(ssdv_t));
s->image_id = image_id;
s->callsign = encode_callsign(callsign);
s->mode = S_ENCODING;
s->type = type;
s->quality = quality;
s->pkt_size = pkt_size;
ssdv_set_packet_conf(s);
/* Prepare the output JPEG tables */
s->ddqt[0] = dload_standard_dqt(s, std_dqt0, s->quality);
s->ddqt[1] = dload_standard_dqt(s, std_dqt1, s->quality);
s->ddht[0][0] = dtblcpy(s, std_dht00, sizeof(std_dht00));
s->ddht[0][1] = dtblcpy(s, std_dht01, sizeof(std_dht01));
s->ddht[1][0] = dtblcpy(s, std_dht10, sizeof(std_dht10));
s->ddht[1][1] = dtblcpy(s, std_dht11, sizeof(std_dht11));
return(SSDV_OK);
}
char ssdv_enc_set_buffer(ssdv_t *s, uint8_t *buffer)
{
s->out = buffer;
s->outp = buffer + SSDV_PKT_SIZE_HEADER;
s->out_len = s->pkt_size_payload;
/* Zero the payload memory */
memset(s->out, 0, s->pkt_size);
/* Flush the output bits */
ssdv_outbits(s, 0, 0);
return(SSDV_OK);
}
char ssdv_enc_get_packet(ssdv_t *s)
{
int r;
uint8_t b;
/* Have we reached the end of the image? */
if(s->state == S_EOI) return(SSDV_EOI);
/* If the output buffer is empty, re-initialise */
if(s->out_len == 0) ssdv_enc_set_buffer(s, s->out);
while(s->in_len)
{
b = *(s->inp++);
s->in_len--;
/* Skip bytes if necessary */
if(s->in_skip) { s->in_skip--; continue; }
switch(s->state)
{
case S_MARKER:
s->marker = (s->marker << 8) | b;
if(s->marker == J_TEM ||
(s->marker >= J_RST0 && s->marker <= J_EOI))
{
/* Marker without data */
s->marker_len = 0;
r = ssdv_have_marker(s);
if(r != SSDV_OK) return(r);
}
else if(s->marker >= J_SOF0 && s->marker <= J_COM)
{
/* All other markers are followed by data */
s->marker_len = 0;
s->state = S_MARKER_LEN;
s->needbits = 16;
}
break;
case S_MARKER_LEN:
s->marker_len = (s->marker_len << 8) | b;
if((s->needbits -= 8) == 0)
{
s->marker_len -= 2;
r = ssdv_have_marker(s);
if(r != SSDV_OK) return(r);
}
break;
case S_MARKER_DATA:
s->marker_data[s->marker_data_len++] = b;
if(s->marker_data_len == s->marker_len)
{
r = ssdv_have_marker_data(s);
if(r != SSDV_OK) return(r);
}
break;
case S_HUFF:
case S_INT:
/* Is the next byte a stuffing byte? Skip it */
/* TODO: Test the next byte is actually 0x00 */
if(b == 0xFF) s->in_skip++;
/* Add the new byte to the work area */
s->workbits = (s->workbits << 8) | b;
s->worklen += 8;
/* Process the new data until more needed, or an error occurs */
while((r = ssdv_process(s)) == SSDV_OK);
if(r == SSDV_BUFFER_FULL || r == SSDV_EOI)
{
uint16_t mcu_id = s->packet_mcu_id;
uint8_t mcu_offset = s->packet_mcu_offset;
uint32_t x;
uint8_t i;
if(mcu_offset != 0xFF && mcu_offset >= s->pkt_size_payload)
{
/* The first MCU begins in the next packet, not this one */
mcu_id = 0xFFFF;
mcu_offset = 0xFF;
s->packet_mcu_offset -= s->pkt_size_payload;
}
else
{
/* Clear the MCU data for the next packet */
s->packet_mcu_id = 0xFFFF;
s->packet_mcu_offset = 0xFF;
}
/* A packet is ready, create the headers */
s->out[0] = 0x55; /* Sync */
s->out[1] = 0x66 + s->type; /* Type */
s->out[2] = s->callsign >> 24;
s->out[3] = s->callsign >> 16;
s->out[4] = s->callsign >> 8;
s->out[5] = s->callsign;
s->out[6] = s->image_id; /* Image ID */
s->out[7] = s->packet_id >> 8; /* Packet ID MSB */
s->out[8] = s->packet_id & 0xFF; /* Packet ID LSB */
s->out[9] = s->width >> 4; /* Width / 16 */
s->out[10] = s->height >> 4; /* Height / 16 */
s->out[11] = 0x00;
s->out[11] |= ((s->quality - 4) & 7) << 3; /* Quality level */
s->out[11] |= (r == SSDV_EOI ? 1 : 0) << 2; /* EOI flag (1 bit) */
s->out[11] |= s->mcu_mode & 0x03; /* MCU mode (2 bits) */
s->out[12] = mcu_offset; /* Next MCU offset */
s->out[13] = mcu_id >> 8; /* MCU ID MSB */
s->out[14] = mcu_id & 0xFF; /* MCU ID LSB */
/* Fill any remaining bytes with noise */
if(s->out_len > 0) ssdv_memset_prng(s->outp, s->out_len);
/* Calculate the CRC codes */
x = crc32(&s->out[1], s->pkt_size_crcdata);
i = 1 + s->pkt_size_crcdata;
s->out[i++] = (x >> 24) & 0xFF;
s->out[i++] = (x >> 16) & 0xFF;
s->out[i++] = (x >> 8) & 0xFF;
s->out[i++] = x & 0xFF;
/* Generate the RS codes */
if(s->type == SSDV_TYPE_NORMAL)
{
encode_rs_8(&s->out[1], &s->out[i], SSDV_PKT_SIZE - s->pkt_size);
}
s->packet_id++;
/* Have we reached the end of the image data? */
if(r == SSDV_EOI) s->state = S_EOI;
return(SSDV_OK);
}
else if(r != SSDV_FEED_ME)
{
/* An error occured */
fprintf(stderr, "ssdv_process() failed: %i\n", r);
return(SSDV_ERROR);
}
break;
case S_EOI:
/* Shouldn't reach this point */
break;
}
}
/* Need more data */
return(SSDV_FEED_ME);
}
char ssdv_enc_feed(ssdv_t *s, uint8_t *buffer, size_t length)
{
s->inp = buffer;
s->in_len = length;
return(SSDV_OK);
}
/*****************************************************************************/
static void ssdv_write_marker(ssdv_t *s, uint16_t id, uint16_t length, const uint8_t *data)
{
ssdv_outbits(s, id, 16);
if(length > 0)
{
ssdv_outbits(s, length + 2, 16);
while(length--) ssdv_outbits(s, *(data++), 8);
}
}
static void ssdv_out_headers(ssdv_t *s)
{
uint8_t *b = &s->stbls[s->stbl_len];
ssdv_write_marker(s, J_SOI, 0, 0);
ssdv_write_marker(s, J_APP0, 14, app0);
ssdv_write_marker(s, J_DQT, 65, s->ddqt[0]); /* DQT Luminance */
ssdv_write_marker(s, J_DQT, 65, s->ddqt[1]); /* DQT Chrominance */
/* Build SOF0 header */
b[0] = 8; /* Precision */
b[1] = s->height >> 8;
b[2] = s->height & 0xFF;
b[3] = s->width >> 8;
b[4] = s->width & 0xFF;
b[5] = 3; /* Components (Y'Cb'Cr) */
b[6] = 1; /* Y */
switch(s->mcu_mode)
{
case 0: b[7] = 0x22; break;
case 1: b[7] = 0x12; break;
case 2: b[7] = 0x21; break;
case 3: b[7] = 0x11; break;
}
b[8] = 0x00;
b[9] = 2; /* Cb */
b[10] = 0x11;
b[11] = 0x01;
b[12] = 3; /* Cr */
b[13] = 0x11;
b[14] = 0x01;
ssdv_write_marker(s, J_SOF0, 15, b); /* SOF0 (Baseline DCT) */
ssdv_write_marker(s, J_DHT, 29, std_dht00); /* DHT (DC Luminance) */
ssdv_write_marker(s, J_DHT, 179, std_dht10); /* DHT (AC Luminance) */
ssdv_write_marker(s, J_DHT, 29, std_dht01); /* DHT (DC Chrominance */
ssdv_write_marker(s, J_DHT, 179, std_dht11); /* DHT (AC Chrominance */
ssdv_write_marker(s, J_SOS, 10, sos);
}
static void ssdv_fill_gap(ssdv_t *s, uint16_t next_mcu)
{
if(s->mcupart > 0 || s->acpart > 0)
{
/* Cleanly end the current MCU part */
if(s->acpart > 0)
{
ssdv_out_jpeg_int(s, 0, 0);
s->mcupart++;
}
/* End the current MCU block */
for(; s->mcupart < s->ycparts + 2; s->mcupart++)
{
if(s->mcupart < s->ycparts) s->component = 0;
else s->component = s->mcupart - s->ycparts + 1;
s->acpart = 0; ssdv_out_jpeg_int(s, 0, 0); /* DC */
s->acpart = 1; ssdv_out_jpeg_int(s, 0, 0); /* AC */
}
s->mcu_id++;
}
/* Pad out missing MCUs */
for(; s->mcu_id < next_mcu; s->mcu_id++)
{
/* End the current MCU block */
for(s->mcupart = 0; s->mcupart < s->ycparts + 2; s->mcupart++)
{
if(s->mcupart < s->ycparts) s->component = 0;
else s->component = s->mcupart - s->ycparts + 1;
s->acpart = 0; ssdv_out_jpeg_int(s, 0, 0); /* DC */
s->acpart = 1; ssdv_out_jpeg_int(s, 0, 0); /* AC */
}
}
}
char ssdv_dec_init(ssdv_t *s, int pkt_size)
{
/* Limit the packet length */
if(pkt_size > SSDV_PKT_SIZE)
{
fprintf(stderr, "Invalid SSDV packet length\n");
return(SSDV_ERROR);
}
memset(s, 0, sizeof(ssdv_t));
s->pkt_size = pkt_size;
/* The packet data should contain only scan data, no headers */
s->state = S_HUFF;
s->mode = S_DECODING;
/* Prepare the source JPEG tables */
s->sdht[0][0] = stblcpy(s, std_dht00, sizeof(std_dht00));
s->sdht[0][1] = stblcpy(s, std_dht01, sizeof(std_dht01));
s->sdht[1][0] = stblcpy(s, std_dht10, sizeof(std_dht10));
s->sdht[1][1] = stblcpy(s, std_dht11, sizeof(std_dht11));
/* Prepare the output JPEG tables */
s->ddht[0][0] = dtblcpy(s, std_dht00, sizeof(std_dht00));
s->ddht[0][1] = dtblcpy(s, std_dht01, sizeof(std_dht01));
s->ddht[1][0] = dtblcpy(s, std_dht10, sizeof(std_dht10));
s->ddht[1][1] = dtblcpy(s, std_dht11, sizeof(std_dht11));
return(SSDV_OK);
}
char ssdv_dec_set_buffer(ssdv_t *s, uint8_t *buffer, size_t length)
{
size_t c = s->outp - s->out;
s->outp = buffer + c;
s->out = buffer;
s->out_len = length - c;
/* Flush the output bits */
ssdv_outbits(s, 0, 0);
return(SSDV_OK);
}
char ssdv_dec_feed(ssdv_t *s, uint8_t *packet)
{
int i = 0, r;
uint8_t b;
uint16_t packet_id;
/* Read the packet header */
packet_id = (packet[7] << 8) | packet[8];
s->packet_mcu_offset = packet[12];
s->packet_mcu_id = (packet[13] << 8) | packet[14];
if(s->packet_mcu_id != 0xFFFF)
{
/* Set the next reset MCU ID */
s->next_reset_mcu = s->packet_mcu_id;
}
/* If this is the first packet, write the JPEG headers */
if(s->packet_id == 0)
{
const char *factor;
char callsign[SSDV_MAX_CALLSIGN + 1];
/* Read the fixed headers from the packet */
s->type = packet[1] - 0x66;
s->callsign = (packet[2] << 24) | (packet[3] << 16) | (packet[4] << 8) | packet[5];
s->image_id = packet[6];
s->width = packet[9] << 4;
s->height = packet[10] << 4;
s->mcu_count = packet[9] * packet[10];
s->quality = ((packet[11] >> 3) & 7) ^ 4;
s->mcu_mode = packet[11] & 0x03;
/* Configure the payload size and CRC position */
ssdv_set_packet_conf(s);
/* Generate the DQT tables */
s->sdqt[0] = sload_standard_dqt(s, std_dqt0, s->quality);
s->sdqt[1] = sload_standard_dqt(s, std_dqt1, s->quality);
s->ddqt[0] = dload_standard_dqt(s, std_dqt0, s->quality);
s->ddqt[1] = dload_standard_dqt(s, std_dqt1, s->quality);
switch(s->mcu_mode & 3)
{
case 0: factor = "2x2"; s->ycparts = 4; break;
case 1: factor = "1x2"; s->ycparts = 2; s->mcu_count *= 2; break;
case 2: factor = "2x1"; s->ycparts = 2; s->mcu_count *= 2; break;
case 3: factor = "1x1"; s->ycparts = 1; s->mcu_count *= 4; break;
}
/* Display information about the image */
fprintf(stderr, "Callsign: %s\n", decode_callsign(callsign, s->callsign));
fprintf(stderr, "Image ID: %02X\n", s->image_id);
fprintf(stderr, "Resolution: %ix%i\n", s->width, s->height);
fprintf(stderr, "MCU blocks: %i\n", s->mcu_count);
fprintf(stderr, "Sampling factor: %s\n", factor);
fprintf(stderr, "Quality level: %d\n", s->quality);
/* Output JPEG headers and enable byte stuffing */
ssdv_out_headers(s);
s->out_stuff = 1;
}
/* Is this not the packet we expected? */
if(packet_id != s->packet_id)
{
if(packet_id < s->packet_id)
{
/* The decoder can only accept packets in the correct order */
fprintf(stderr, "Packets are not in order. %i > %i\n", s->packet_id - 1, packet_id);
return(SSDV_FEED_ME);
}
/* One or more packets have been lost! */
fprintf(stderr, "Gap detected between packets %i and %i\n", s->packet_id - 1, packet_id);
/* If this packet has no new MCU, ignore */
if(s->packet_mcu_id == 0xFFFF) return(SSDV_FEED_ME);
/* Fill the gap left by the missing packet */
ssdv_fill_gap(s, s->packet_mcu_id);
/* Skip the bytes of the lost MCU */
i = s->packet_mcu_offset;
/* Reset the JPEG decoder state */
s->state = S_HUFF;
s->component = 0;
s->mcupart = 0;
s->acpart = 0;
s->accrle = 0;
s->packet_id = packet_id;
}
/* Feed the JPEG data into the processor */
for(; i < s->pkt_size_payload; i++)
{
if(i == s->packet_mcu_offset)
{
/* The first MCU in a packet is byte aligned,
* any old bits should be dropped. */
s->workbits = s->worklen = 0;
/* Abandon the packet if the MCU index is not what it should be. */
if(s->mcu_id != s->packet_mcu_id)
{
fprintf(stderr, "Unexpected MCU ID in packet %d.\n", packet_id);
return(SSDV_FEED_ME);
}
}
b = packet[SSDV_PKT_SIZE_HEADER + i];
/* Add the new byte to the work area */
s->workbits = (s->workbits << 8) | b;
s->worklen += 8;
/* Process the new data until more needed, or an error occurs */
while((r = ssdv_process(s)) == SSDV_OK);
if(r == SSDV_BUFFER_FULL)
{
/* Realloc memory */
}
else if(r == SSDV_EOI)
{
/* All done! */
return(SSDV_OK);
}
else if(r != SSDV_FEED_ME)
{
/* An error occured */
fprintf(stderr, "ssdv_process() failed: %i\n", r);
return(SSDV_ERROR);
}
}
/* The next packet to expect... */
s->packet_id++;
return(SSDV_FEED_ME);
}
char ssdv_dec_get_jpeg(ssdv_t *s, uint8_t **jpeg, size_t *length)
{
/* Is the image complete? */
if(s->mcu_id < s->mcu_count) ssdv_fill_gap(s, s->mcu_count);
/* Sync, and final EOI header and return */
ssdv_outbits_sync(s);
s->out_stuff = 0;
ssdv_write_marker(s, J_EOI, 0, 0);
*jpeg = s->out;
*length = (size_t) (s->outp - s->out);
return(SSDV_OK);
}
char ssdv_dec_is_packet(uint8_t *packet, int pkt_size, int *errors)
{
uint8_t pkt[SSDV_PKT_SIZE];
uint8_t type;
uint16_t pkt_size_payload;
uint16_t pkt_size_crcdata;
ssdv_packet_info_t p;
uint32_t x;
int i;
/* Testing is destructive, work on a copy */
memcpy(pkt, packet, pkt_size);
pkt[0] = 0x55;
type = SSDV_TYPE_INVALID;
if(pkt[1] == 0x66 + SSDV_TYPE_NOFEC)
{
/* Test for a valid NOFEC packet */
pkt_size_payload = pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC;
pkt_size_crcdata = SSDV_PKT_SIZE_HEADER + pkt_size_payload - 1;
/* No FEC scan */
if(errors) *errors = 0;
/* Test the checksum */
x = crc32(&pkt[1], pkt_size_crcdata);
i = 1 + pkt_size_crcdata;
if(x == (pkt[i + 3] | (pkt[i + 2] << 8) | (pkt[i + 1] << 16) | (pkt[i] << 24)))
{
/* Valid, set the type and continue */
type = SSDV_TYPE_NOFEC;
}
}
else if(pkt[1] == 0x66 + SSDV_TYPE_NORMAL)
{
/* Test for a valid NORMAL packet */
pkt_size_payload = pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC - SSDV_PKT_SIZE_RSCODES;
pkt_size_crcdata = SSDV_PKT_SIZE_HEADER + pkt_size_payload - 1;
/* No FEC scan */
if(errors) *errors = 0;
/* Test the checksum */
x = crc32(&pkt[1], pkt_size_crcdata);
i = 1 + pkt_size_crcdata;
if(x == (pkt[i + 3] | (pkt[i + 2] << 8) | (pkt[i + 1] << 16) | (pkt[i] << 24)))
{
/* Valid, set the type and continue */
type = SSDV_TYPE_NORMAL;
}
}
if(type == SSDV_TYPE_INVALID)
{
/* Test for a valid NORMAL packet with correctable errors */
pkt_size_payload = pkt_size - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC - SSDV_PKT_SIZE_RSCODES;
pkt_size_crcdata = SSDV_PKT_SIZE_HEADER + pkt_size_payload - 1;
/* Run the reed-solomon decoder */
pkt[1] = 0x66 + SSDV_TYPE_NORMAL;
i = decode_rs_8(&pkt[1], 0, 0, SSDV_PKT_SIZE - pkt_size);
if(i < 0) return(-1); /* Reed-solomon decoder failed */
if(errors) *errors = i;
/* Test the checksum */
x = crc32(&pkt[1], pkt_size_crcdata);
i = 1 + pkt_size_crcdata;
if(x == (pkt[i + 3] | (pkt[i + 2] << 8) | (pkt[i + 1] << 16) | (pkt[i] << 24)))
{
/* Valid, set the type and continue */
type = SSDV_TYPE_NORMAL;
}
}
if(type == SSDV_TYPE_INVALID)
{
/* All attempts to read the packet have failed */
return(-1);
}
/* Sanity checks */
ssdv_dec_header(&p, pkt);
if(p.type != type) return(-1);
if(p.width == 0 || p.height == 0) return(-1);
if(p.mcu_id != 0xFFFF)
{
if(p.mcu_id >= p.mcu_count) return(-1);
if(p.mcu_offset >= pkt_size_payload) return(-1);
}
/* Appears to be a valid packet! Copy it back */
memcpy(packet, pkt, pkt_size);
return(0);
}
void ssdv_dec_header(ssdv_packet_info_t *info, uint8_t *packet)
{
info->type = packet[1] - 0x66;
info->callsign = (packet[2] << 24) | (packet[3] << 16) | (packet[4] << 8) | packet[5];
decode_callsign(info->callsign_s, info->callsign);
info->image_id = packet[6];
info->packet_id = (packet[7] << 8) | packet[8];
info->width = packet[9] << 4;
info->height = packet[10] << 4;
info->eoi = (packet[11] >> 2) & 1;
info->quality = ((packet[11] >> 3) & 7) ^ 4;
info->mcu_mode = packet[11] & 0x03;
info->mcu_offset = packet[12];
info->mcu_id = (packet[13] << 8) | packet[14];
info->mcu_count = packet[9] * packet[10];
if(info->mcu_mode == 1 || info->mcu_mode == 2) info->mcu_count *= 2;
else if(info->mcu_mode == 3) info->mcu_count *= 4;
}
/*****************************************************************************/
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