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comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/t4.h @ 5:f762bf195c4b

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import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
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4:26cd8f1ef0b1 5:f762bf195c4b
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * t4.h - definitions for T.4 fax processing
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2003 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2, as
14 * published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: t4.h,v 1.29 2006/10/24 13:45:28 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_T4_H_)
31 #define _T4_H_
32
33 /*! \page t4_page T.4 image compression and decompression
34
35 \section t4_page_sec_1 What does it do?
36 The T.4 image compression and decompression routines implement the 1D and 2D
37 encoding methods defined in ITU specification T.4. They also implement the pure
38 2D encoding method defined in T.6. These are image compression algorithms used
39 for FAX transmission.
40
41 \section t4_page_sec_1 How does it work?
42 */
43
44 #define T4_COMPRESSION_ITU_T4_1D 1
45 #define T4_COMPRESSION_ITU_T4_2D 2
46 #define T4_COMPRESSION_ITU_T6 3
47
48 #define T4_X_RESOLUTION_R4 4019
49 #define T4_X_RESOLUTION_R8 8037
50 #define T4_X_RESOLUTION_R16 16074
51
52 #define T4_Y_RESOLUTION_STANDARD 3850
53 #define T4_Y_RESOLUTION_FINE 7700
54 #define T4_Y_RESOLUTION_SUPERFINE 15400
55
56 /*!
57 T.4 FAX compression/decompression descriptor. This defines the working state
58 for a single instance of a T.4 FAX compression or decompression channel.
59 */
60 typedef struct
61 {
62 /* "Background" information about the FAX, which can be stored in a TIFF file. */
63 /*! \brief The vendor of the machine which produced the TIFF file. */
64 const char *vendor;
65 /*! \brief The model of machine which produced the TIFF file. */
66 const char *model;
67 /*! \brief The local ident string. */
68 const char *local_ident;
69 /*! \brief The remote end's ident string. */
70 const char *far_ident;
71 /*! \brief The FAX sub-address. */
72 const char *sub_address;
73 /*! \brief The text which will be used in FAX page header. No text results
74 in no header line. */
75 const char *header_info;
76
77 /*! \brief The type of compression used between the FAX machines. */
78 int line_encoding;
79 /*! \brief The minimum number of bits per scan row. This is a timing thing
80 for hardware FAX machines. */
81 int min_scan_line_bits;
82
83 int output_compression;
84 int output_t4_options;
85
86 time_t page_start_time;
87
88 int bytes_per_row;
89 int image_size;
90 int image_buffer_size;
91 uint8_t *image_buffer;
92
93 TIFF *tiff_file;
94 const char *file;
95 int start_page;
96 int stop_page;
97
98 int pages_transferred;
99 /*! Column-to-column (X) resolution in pixels per metre. */
100 int x_resolution;
101 /*! Row-to-row (Y) resolution in pixels per metre. */
102 int y_resolution;
103 /*! Width of the current page, in pixels. */
104 int image_width;
105 /*! Current pixel row number. */
106 int row;
107 /*! Total pixel rows in the current page. */
108 int image_length;
109 /*! The current number of consecutive bad rows. */
110 int curr_bad_row_run;
111 /*! The longest run of consecutive bad rows seen in the current page. */
112 int longest_bad_row_run;
113 /*! The total number of bad rows in the current page. */
114 int bad_rows;
115
116 /* Decode state */
117 uint32_t bits_to_date;
118 int bits;
119
120 /*! \brief This variable is set if we are treating the current row as a 2D encoded
121 one. */
122 int row_is_2d;
123 int its_black;
124 int row_len;
125 /*! \brief This variable is used to record the fact we have seen at least one EOL
126 since we started decoding. We will not try to interpret the received
127 data as an image until we have seen the first EOL. */
128 int first_eol_seen;
129 /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
130 reaches six, this is the end of the image. */
131 int consecutive_eols;
132
133 /*! \brief B&W runs for reference line */
134 uint32_t *ref_runs;
135 /*! \brief B&W runs for current line */
136 uint32_t *cur_runs;
137
138 uint32_t *pa;
139 uint32_t *pb;
140 int a0;
141 int b1;
142 /*! \brief The length of the current run of black or white. */
143 int run_length;
144 int black_white;
145
146 uint32_t data;
147 int bit;
148
149 /*! \brief A point into the image buffer indicating where the last row begins */
150 int last_row_starts_at;
151 /*! \brief A point into the image buffer indicating where the current row begins */
152 int row_starts_at;
153
154 /* Encode state */
155
156 /*! Pointer to the buffer for the current pixel row. */
157 uint8_t *row_buf;
158
159 int bit_pos;
160 int bit_ptr;
161
162 /*! \brief The reference pixel row for 2D encoding. */
163 uint8_t *ref_row_buf;
164 /*! \brief The maximum contiguous rows that will be 2D encoded. */
165 int max_rows_to_next_1d_row;
166 /*! \brief Number of rows left that can be 2D encoded, before a 1D encoded row
167 must be used. */
168 int rows_to_next_1d_row;
169 /*! \brief The minimum number of encoded bits per row. */
170 int min_row_bits;
171 /*! \brief The current number of bits in the current encoded row. */
172 int row_bits;
173
174 /*! \brief Error and flow logging control */
175 logging_state_t logging;
176 } t4_state_t;
177
178 /*!
179 T.4 FAX compression/decompression statistics.
180 */
181 typedef struct
182 {
183 /*! \brief The number of pages transferred so far. */
184 int pages_transferred;
185 /*! \brief The number of horizontal pixels in the most recent page. */
186 int width;
187 /*! \brief The number of vertical pixels in the most recent page. */
188 int length;
189 /*! \brief The number of bad pixel rows in the most recent page. */
190 int bad_rows;
191 /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
192 int longest_bad_row_run;
193 /*! \brief The horizontal resolution of the page in pixels per metre */
194 int x_resolution;
195 /*! \brief The vertical resolution of the page in pixels per metre */
196 int y_resolution;
197 /*! \brief The type of compression used between the FAX machines */
198 int encoding;
199 /*! \brief The size of the image, in bytes */
200 int image_size;
201 } t4_stats_t;
202
203 #ifdef __cplusplus
204 extern "C" {
205 #endif
206
207 /*! \brief Allocate a T.4 transmit handling context, and
208 initialise it.
209 \param file The name of the file to be received.
210 \param output_encoding The output encoding.
211 \return The T.4 context, or NULL. */
212 t4_state_t *t4_rx_create(const char *file, int output_encoding);
213
214 /*! \brief Prepare for reception of a document.
215 \param s The T.4 context.
216 \param file The name of the file to be received.
217 \param output_encoding The output encoding.
218 \return 0 for success, otherwise -1. */
219 int t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
220
221 /*! \brief Prepare to receive the next page of the current document.
222 \param s The T.4 context.
223 \return zero for success, -1 for failure. */
224 int t4_rx_start_page(t4_state_t *s);
225
226 /*! \brief Put a bit of the current document page.
227 \param s The T.4 context.
228 \param bit The data bit.
229 \return TRUE when the bit ends the document page, otherwise FALSE. */
230 int t4_rx_put_bit(t4_state_t *s, int bit);
231
232 /*! \brief Complete the reception of a page.
233 \param s The T.4 receive context.
234 \return 0 for success, otherwise -1. */
235 int t4_rx_end_page(t4_state_t *s);
236
237 /*! \brief End reception of a document. Tidy up, close the file and
238 free the context. This should be used to end T.4 reception
239 started with t4_rx_create.
240 \param s The T.4 receive context.
241 \return 0 for success, otherwise -1. */
242 int t4_rx_delete(t4_state_t *s);
243
244 /*! \brief End reception of a document. Tidy up and close the file.
245 This should be used to end T.4 reception started with
246 t4_rx_init.
247 \param s The T.4 context.
248 \return 0 for success, otherwise -1. */
249 int t4_rx_end(t4_state_t *s);
250
251 /*! \brief Set the encoding for the received data.
252 \param s The T.4 context.
253 \param encoding The encoding. */
254 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
255
256 /*! \brief Set the expected width of the received image, in pixel columns.
257 \param s The T.4 context.
258 \param columns The number of pixels across the image. */
259 void t4_rx_set_image_width(t4_state_t *s, int width);
260
261 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
262 \param s The T.4 context.
263 \param resolution The resolution, in pixels per metre. */
264 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
265
266 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
267 \param s The T.4 context.
268 \param resolution The resolution, in pixels per metre. */
269 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
270
271 /*! \brief Set the sub-address of the fax, for inclusion in the file.
272 \param s The T.4 context.
273 \param sub_address The sub-address string. */
274 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
275
276 /*! \brief Set the identity of the remote machine, for inclusion in the file.
277 \param s The T.4 context.
278 \param ident The identity string. */
279 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
280
281 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
282 \param s The T.4 context.
283 \param vendor The vendor string, or NULL. */
284 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
285
286 /*! \brief Set the model of the remote machine, for inclusion in the file.
287 \param s The T.4 context.
288 \param model The model string, or NULL. */
289 void t4_rx_set_model(t4_state_t *s, const char *model);
290
291 /*! \brief Allocate a T.4 receive handling context, and
292 initialise it.
293 \param s The T.4 context.
294 \param file The name of the file to be sent.
295 \return 0 for success, otherwise -1. */
296 t4_state_t *t4_tx_create(const char *file, int start_page, int stop_page);
297
298 /*! \brief Prepare for transmission of a document.
299 \param s The T.4 context.
300 \param file The name of the file to be sent.
301 \param start_page The first page to send. -1 for no restriction.
302 \param stop_page The last page to send. -1 for no restriction.
303 \return The T.4 context, or NULL. */
304 int t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
305
306 /*! \brief Prepare to send the next page of the current document.
307 \param s The T.4 context.
308 \return zero for success, -1 for failure. */
309 int t4_tx_start_page(t4_state_t *s);
310
311 /*! \brief Prepare the current page for a resend.
312 \param s The T.4 context.
313 \return zero for success, -1 for failure. */
314 int t4_tx_restart_page(t4_state_t *s);
315
316 /*! \brief Check for the existance of the next page. This information can
317 be needed before it is determined that the current page is finished with.
318 \param s The T.4 context.
319 \return zero for next page found, -1 for failure. */
320 int t4_tx_more_pages(t4_state_t *s);
321
322 /*! \brief Complete the sending of a page.
323 \param s The T.4 context.
324 \return zero for success, -1 for failure. */
325 int t4_tx_end_page(t4_state_t *s);
326
327 /*! \brief Get the next bit of the current document page. The document will
328 be padded for the current minimum scan line time. If the
329 file does not contain an RTC (return to control) code at
330 the end of the page, one will be added.
331 \param s The T.4 context.
332 \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
333 set (i.e. the returned value is 2 or 3). */
334 int t4_tx_get_bit(t4_state_t *s);
335
336 /*! \brief Return the next bit of the current document page, without actually
337 moving forward in the buffer. The document will be padded for the
338 current minimum scan line time. If the file does not contain an
339 RTC (return to control) code at the end of the page, one will be
340 added.
341 \param s The T.4 context.
342 \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
343 set (i.e. the returned value is 2 or 3). */
344 int t4_tx_check_bit(t4_state_t *s);
345
346 /*! \brief End the transmission of a document. Tidy up, close the file and
347 free the context. This should be used to end T.4 transmission
348 started with t4_tx_create.
349 \param s The T.4 context.
350 \return 0 for success, otherwise -1. */
351 int t4_tx_delete(t4_state_t *s);
352
353 /*! \brief End the transmission of a document. Tidy up and close the file.
354 This should be used to end T.4 transmission started with t4_tx_init.
355 \param s The T.4 context.
356 \return 0 for success, otherwise -1. */
357 int t4_tx_end(t4_state_t *s);
358
359 /*! \brief Set the encoding for the encoded data.
360 \param s The T.4 context.
361 \param encoding The encoding. */
362 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
363
364 /*! \brief Set the minimum number of encoded bits per row. This allows the
365 makes the encoding process to be set to comply with the minimum row
366 time specified by a remote receiving machine.
367 \param s The T.4 context.
368 \param bits The minimum number of bits per row. */
369 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
370
371 /*! \brief Set the identity of the local machine, for inclusion in page headers.
372 \param s The T.4 context.
373 \param ident The identity string. */
374 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
375
376 /*! Set the info field, included in the header line included in each page of an encoded
377 FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
378 are automatically included in the header. If the header info is set to NULL or a zero
379 length string, no header lines will be added to the encoded FAX.
380 \brief Set the header info.
381 \param s The T.4 context.
382 \param info A string, of up to 50 bytes, which will form the info field. */
383 void t4_tx_set_header_info(t4_state_t *s, const char *info);
384
385 /*! \brief Get the row-to-row (y) resolution of the current page.
386 \param s The T.4 context.
387 \return The resolution, in pixels per metre. */
388 int t4_tx_get_y_resolution(t4_state_t *s);
389
390 /*! \brief Get the column-to-column (x) resolution of the current page.
391 \param s The T.4 context.
392 \return The resolution, in pixels per metre. */
393 int t4_tx_get_x_resolution(t4_state_t *s);
394
395 /*! \brief Get the width of the current page, in pixel columns.
396 \param s The T.4 context.
397 \return The number of columns. */
398 int t4_tx_get_image_width(t4_state_t *s);
399
400 /*! Get the current image transfer statistics.
401 \brief Get the current transfer statistics.
402 \param s The T.4 context.
403 \param t A pointer to a statistics structure. */
404 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
405
406 /*! Get the short text name of an encoding format.
407 \brief Get the short text name of an encoding format.
408 \param encoding The encoding type.
409 \return A pointer to the string. */
410 const char *t4_encoding_to_str(int encoding);
411
412 #ifdef __cplusplus
413 }
414 #endif
415
416 #endif
417 /*- End of file ------------------------------------------------------------*/

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