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Add support for multiple subsampling formats. Not backwards compatible!
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@fsphil
fsphil committed Feb 25, 2012
1 parent 604f4f1 commit 2df18c5
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1 change: 0 additions & 1 deletion README
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,6 @@ TODO

* Allow the decoder to handle multiple images in the input stream.
* Experiment with adaptive or multiple huffman tables.
* Support more than one subsampling configuration. (4 modes / 2 bits)
* Quality setting (4 bit / 16 quality levels).
* Add a callsign field to each packet.

100 changes: 71 additions & 29 deletions ssdv.c
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@

/* SSDV - Slow Scan Digital Video */
/*=======================================================================*/
/* Copyright 2011 Philip Heron <phil@sanslogic.co.uk */
/* Copyright 2011-2012 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 */
Expand Down Expand Up @@ -314,7 +314,7 @@ static char ssdv_process(ssdv_t *s)
if(symbol == 0x00)
{
/* No change in DC from last block */
if(s->reset_mcu == s->mcu_id && (s->mcupart == 0 || s->mcupart == 4 || s->mcupart == 5))
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
Expand Down Expand Up @@ -376,7 +376,7 @@ static char ssdv_process(ssdv_t *s)

if(s->acpart == 0) /* DC */
{
if(s->reset_mcu == s->mcu_id && (s->mcupart == 0 || s->mcupart == 4 || s->mcupart == 5))
if(s->reset_mcu == s->mcu_id && (s->mcupart == 0 || s->mcupart >= s->ycparts))
{
if(s->mode == S_ENCODING)
{
Expand Down Expand Up @@ -450,7 +450,7 @@ static char ssdv_process(ssdv_t *s)
if(s->acpart >= 64)
{
/* Reached the end of this MCU part */
if(++s->mcupart == 6)
if(++s->mcupart == s->ycparts + 2)
{
s->mcupart = 0;
s->mcu_id++;
Expand Down Expand Up @@ -480,8 +480,8 @@ static char ssdv_process(ssdv_t *s)
}
}

if(s->mcupart < 4) s->component = 0;
else s->component = s->mcupart - 3;
if(s->mcupart < s->ycparts) s->component = 0;
else s->component = s->mcupart - s->ycparts + 1;

s->acpart = 0;
s->accrle = 0;
Expand Down Expand Up @@ -574,14 +574,10 @@ static char ssdv_have_marker_data(ssdv_t *s)
s->width = (d[3] << 8) | d[4];
s->height = (d[1] << 8) | d[2];

/* Calculate number of MCU blocks in this image -- assumes 16x16 blocks */
s->mcu_count = (s->width >> 4) * (s->height >> 4);

/* 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]);
fprintf(stderr, "MCU blocks: %i\n", s->mcu_count);

/* The image must have a precision of 8 */
if(d[0] != 8)
Expand Down Expand Up @@ -624,11 +620,19 @@ static char ssdv_have_marker_data(ssdv_t *s)

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 component must have a factor of 2x2 and the rest 1x1 */
if(dq[0] == 1 && dq[1] != 0x22)
/* The first (Y) component must have a factor of 2x2,2x1,1x2 or 1x1 */
if(dq[0] == 1)
{
fprintf(stderr, "Error: Component 1 sampling factor must be 2x2\n");
return(SSDV_ERROR);
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(dq[0] != 1 && dq[1] != 0x11)
{
Expand All @@ -637,6 +641,17 @@ static char ssdv_have_marker_data(ssdv_t *s)
}
}

/* Calculate number of MCU blocks in this image */
switch(s->mcu_mode)
{
case 0: s->mcu_count = (s->width >> 4) * (s->height >> 4); break;
case 1: s->mcu_count = (s->width >> 4) * (s->height >> 3); break;
case 2: s->mcu_count = (s->width >> 3) * (s->height >> 4); break;
case 3: s->mcu_count = (s->width >> 3) * (s->height >> 3); break;
}

fprintf(stderr, "MCU blocks: %i\n", s->mcu_count);

break;

case J_SOS:
Expand Down Expand Up @@ -838,10 +853,11 @@ char ssdv_enc_get_packet(ssdv_t *s)
s->out[4] = s->packet_id & 0xFF; /* Packet ID LSB */
s->out[5] = s->width >> 4; /* Width / 16 */
s->out[6] = s->height >> 4; /* Height / 16 */
s->out[7] = mcu_offset >> 8; /* Next MCU offset MSB */
s->out[8] = mcu_offset & 0xFF; /* Next MCU offset LSB */
s->out[9] = mcu_id >> 8; /* MCU ID MSB */
s->out[10] = mcu_id & 0xFF; /* MCU ID LSB */
s->out[7] = s->mcu_mode & 0x03; /* MCU mode (2 bits) */
s->out[8] = mcu_offset >> 8; /* Next MCU offset MSB */
s->out[9] = mcu_offset & 0xFF; /* Next MCU offset LSB */
s->out[10] = mcu_id >> 8; /* MCU ID MSB */
s->out[11] = 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);
Expand Down Expand Up @@ -917,7 +933,13 @@ static void ssdv_out_headers(ssdv_t *s)
b[4] = s->width & 0xFF;
b[5] = 3; /* Components (Y'Cb'Cr) */
b[6] = 1; /* Y */
b[7] = 0x22;
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;
Expand Down Expand Up @@ -946,10 +968,10 @@ static void ssdv_fill_gap(ssdv_t *s, uint16_t next_mcu)
}

/* End the current MCU block */
for(; s->mcupart < 6; s->mcupart++)
for(; s->mcupart < s->ycparts + 2; s->mcupart++)
{
if(s->mcupart < 4) s->component = 0;
else s->component = s->mcupart - 3;
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 */
}
Expand All @@ -961,10 +983,10 @@ static void ssdv_fill_gap(ssdv_t *s, uint16_t next_mcu)
for(; s->mcu_id < next_mcu; s->mcu_id++)
{
/* End the current MCU block */
for(s->mcupart = 0; s->mcupart < 6; s->mcupart++)
for(s->mcupart = 0; s->mcupart < s->ycparts + 2; s->mcupart++)
{
if(s->mcupart < 4) s->component = 0;
else s->component = s->mcupart - 3;
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 */
}
Expand Down Expand Up @@ -1004,19 +1026,36 @@ char ssdv_dec_feed(ssdv_t *s, uint8_t *packet)

/* Read the packet header */
packet_id = (packet[3] << 8) | packet[4];
s->packet_mcu_offset = (packet[7] << 8) | packet[8];
s->packet_mcu_id = (packet[9] << 8) | packet[10];
s->packet_mcu_offset = (packet[8] << 8) | packet[9];
s->packet_mcu_id = (packet[10] << 8) | packet[11];

if(s->packet_mcu_id != 0xFFFF) s->reset_mcu = s->packet_mcu_id;

/* If this is the first packet, write the JPEG headers */
if(s->packet_id == 0)
{
const char *factor;

/* Read the fixed headers from the packet */
s->image_id = packet[2];
s->width = packet[5] << 4;
s->height = packet[6] << 4;
s->mcu_count = packet[5] * packet[6];
s->mcu_mode = packet[7] & 0x03;

switch(s->mcu_mode)
{
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, "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);

/* Output JPEG headers and enable byte stuffing */
ssdv_out_headers(s);
Expand Down Expand Up @@ -1160,9 +1199,12 @@ void ssdv_dec_header(ssdv_packet_info_t *info, uint8_t *packet)
info->packet_id = (packet[3] << 8) | packet[4];
info->width = packet[5] << 4;
info->height = packet[6] << 4;
info->mcu_offset = (packet[7] << 8) | packet[8];
info->mcu_id = (packet[9] << 8) | packet[10];
info->mcu_mode = packet[7] & 0x03;
info->mcu_offset = (packet[8] << 8) | packet[9];
info->mcu_id = (packet[10] << 8) | packet[11];
info->mcu_count = packet[5] * packet[6];
if(info->mcu_mode == 1 || info->mcu_mode == 2) info->mcu_count *= 2;
else if(info->mcu_mode == 3) info->mcu_count *= 4;
}

/*****************************************************************************/
Expand Down
7 changes: 5 additions & 2 deletions ssdv.h
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@

/* SSDV - Slow Scan Digital Video */
/*=======================================================================*/
/* Copyright 2011 Philip Heron <phil@sanslogic.co.uk */
/* Copyright 2011-2012 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 */
Expand Down Expand Up @@ -33,7 +33,7 @@ extern "C" {

/* Packet details */
#define SSDV_PKT_SIZE (0x100)
#define SSDV_PKT_SIZE_HEADER (0x0B)
#define SSDV_PKT_SIZE_HEADER (0x0C)
#define SSDV_PKT_SIZE_CRC (0x02)
#define SSDV_PKT_SIZE_RSCODES (0x20)
#define SSDV_PKT_SIZE_PAYLOAD (SSDV_PKT_SIZE - SSDV_PKT_SIZE_HEADER - SSDV_PKT_SIZE_CRC - SSDV_PKT_SIZE_RSCODES)
Expand All @@ -48,6 +48,7 @@ typedef struct
uint16_t height;
uint8_t image_id;
uint16_t packet_id;
uint8_t mcu_mode; /* 0 = 2x2, 1 = 2x1, 2 = 1x2, 3 = 1x1 */
uint16_t mcu_id;
uint16_t mcu_count;
uint16_t packet_mcu_id;
Expand Down Expand Up @@ -86,6 +87,7 @@ typedef struct
uint8_t *marker_data; /* Where to copy marker data too */
uint16_t marker_data_len; /* How much is there */
uint8_t component; /* 0 = Y, 1 = Cb, 2 = Cr */
uint8_t ycparts; /* Number of Y component parts per MCU */
uint8_t mcupart; /* 0-3 = Y, 4 = Cb, 5 = Cr */
uint8_t acpart; /* 0 - 64; 0 = DC, 1 - 64 = AC */
int dc[COMPONENTS]; /* DC value for each component */
Expand All @@ -110,6 +112,7 @@ typedef struct {
uint16_t packet_id;
uint16_t width;
uint16_t height;
uint16_t mcu_mode;
uint16_t mcu_offset;
uint16_t mcu_id;
uint16_t mcu_count;
Expand Down

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