t4.h

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00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * t4.h - definitions for T.4 fax processing
00005  *
00006  * Written by Steve Underwood <steveu@coppice.org>
00007  *
00008  * Copyright (C) 2003 Steve Underwood
00009  *
00010  * All rights reserved.
00011  *
00012  * This program is free software; you can redistribute it and/or modify
00013  * it under the terms of the GNU Lesser General Public License version 2.1,
00014  * as published by the Free Software Foundation.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU Lesser General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU Lesser General Public
00022  * License along with this program; if not, write to the Free Software
00023  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00024  *
00025  * $Id: t4.h,v 1.59 2009/04/12 09:12:10 steveu Exp $
00026  */
00027 
00028 /*! \file */
00029 
00030 #if !defined(_SPANDSP_T4_H_)
00031 #define _SPANDSP_T4_H_
00032 
00033 /*! \page t4_page T.4 image compression and decompression
00034 
00035 \section t4_page_sec_1 What does it do?
00036 The T.4 image compression and decompression routines implement the 1D and 2D
00037 encoding methods defined in ITU specification T.4. They also implement the pure
00038 2D encoding method defined in T.6. These are image compression algorithms used
00039 for FAX transmission.
00040 
00041 \section t4_page_sec_1 How does it work?
00042 */
00043 
00044 typedef int (*t4_row_read_handler_t)(void *user_data, uint8_t buf[], size_t len);
00045 typedef int (*t4_row_write_handler_t)(void *user_data, const uint8_t buf[], size_t len);
00046 
00047 /*! Supported compression modes. */
00048 typedef enum
00049 {
00050     T4_COMPRESSION_ITU_T4_1D = 1,
00051     T4_COMPRESSION_ITU_T4_2D = 2,
00052     T4_COMPRESSION_ITU_T6 = 3
00053 } t4_image_compression_t;
00054 
00055 /*! Supported X resolutions, in pixels per metre. */
00056 typedef enum
00057 {
00058     T4_X_RESOLUTION_R4 = 4016,
00059     T4_X_RESOLUTION_R8 = 8031,
00060     T4_X_RESOLUTION_300 = 11811,
00061     T4_X_RESOLUTION_R16 = 16063,
00062     T4_X_RESOLUTION_600 = 23622,
00063     T4_X_RESOLUTION_800 = 31496,
00064     T4_X_RESOLUTION_1200 = 47244
00065 } t4_image_x_resolution_t;
00066 
00067 /*! Supported Y resolutions, in pixels per metre. */
00068 typedef enum
00069 {
00070     T4_Y_RESOLUTION_STANDARD = 3850,
00071     T4_Y_RESOLUTION_FINE = 7700,
00072     T4_Y_RESOLUTION_300 = 11811,
00073     T4_Y_RESOLUTION_SUPERFINE = 15400,  /* 400 is 15748 */
00074     T4_Y_RESOLUTION_600 = 23622,
00075     T4_Y_RESOLUTION_800 = 31496,
00076     T4_Y_RESOLUTION_1200 = 47244
00077 } t4_image_y_resolution_t;
00078 
00079 /*!
00080     Exact widths in PELs for the difference resolutions, and page widths.
00081     Note:
00082         The A4 widths also apply to North American letter and legal.
00083         The R4 resolution widths are not supported in recent versions of T.30
00084         Only images of exactly these widths are acceptable for FAX transmisson.
00085 
00086     R4    864 pels/215mm for ISO A4, North American Letter and Legal
00087     R4   1024 pels/255mm for ISO B4
00088     R4   1216 pels/303mm for ISO A3
00089     R8   1728 pels/215mm for ISO A4, North American Letter and Legal
00090     R8   2048 pels/255mm for ISO B4
00091     R8   2432 pels/303mm for ISO A3
00092     R16  3456 pels/215mm for ISO A4, North American Letter and Legal
00093     R16  4096 pels/255mm for ISO B4
00094     R16  4864 pels/303mm for ISO A3
00095 */
00096 typedef enum
00097 {
00098     T4_WIDTH_R4_A4 = 864,
00099     T4_WIDTH_R4_B4 = 1024,
00100     T4_WIDTH_R4_A3 = 1216,
00101     T4_WIDTH_R8_A4 = 1728,
00102     T4_WIDTH_R8_B4 = 2048,
00103     T4_WIDTH_R8_A3 = 2432,
00104     T4_WIDTH_300_A4 = 2592,
00105     T4_WIDTH_300_B4 = 3072,
00106     T4_WIDTH_300_A3 = 3648,
00107     T4_WIDTH_R16_A4 = 3456,
00108     T4_WIDTH_R16_B4 = 4096,
00109     T4_WIDTH_R16_A3 = 4864,
00110     T4_WIDTH_600_A4 = 5184,
00111     T4_WIDTH_600_B4 = 6144,
00112     T4_WIDTH_600_A3 = 7296,
00113     T4_WIDTH_1200_A4 = 10368,
00114     T4_WIDTH_1200_B4 = 12288,
00115     T4_WIDTH_1200_A3 = 14592
00116 } t4_image_width_t;
00117 
00118 /*!
00119     Length of the various supported paper sizes, in pixels at the various Y resolutions.
00120     Paper sizes are
00121         A4 (215mm x 297mm)
00122         B4 (255mm x 364mm)
00123         A3 (303mm x 418.56mm)
00124         North American Letter (215.9mm x 279.4mm)
00125         North American Legal (215.9mm x 355.6mm)
00126         Unlimited
00127 
00128     T.4 does not accurately define the maximum number of scan lines in a page. A wide
00129     variety of maximum row counts are used in the real world. It is important not to
00130     set our sending limit too high, or a receiving machine might split pages. It is
00131     important not to set it too low, or we might clip pages.
00132 
00133     Values seen for standard resolution A4 pages include 1037, 1045, 1109, 1126 and 1143.
00134     1109 seems the most-popular.  At fine res 2150, 2196, 2200, 2237, 2252-2262, 2264,
00135     2286, and 2394 are used. 2255 seems the most popular. We try to use balanced choices
00136     here.
00137 */
00138 typedef enum
00139 {
00140     /* A4 is 297mm long */
00141     T4_LENGTH_STANDARD_A4 = 1143,
00142     T4_LENGTH_FINE_A4 = 2286,
00143     T4_LENGTH_300_A4 = 4665,
00144     T4_LENGTH_SUPERFINE_A4 = 4573,
00145     T4_LENGTH_600_A4 = 6998,
00146     T4_LENGTH_800_A4 = 9330,
00147     T4_LENGTH_1200_A4 = 13996,
00148     /* B4 is 364mm long */
00149     T4_LENGTH_STANDARD_B4 = 1401,
00150     T4_LENGTH_FINE_B4 = 2802,
00151     T4_LENGTH_300_B4 = 0,
00152     T4_LENGTH_SUPERFINE_B4 = 5605,
00153     T4_LENGTH_600_B4 = 0,
00154     T4_LENGTH_800_B4 = 0,
00155     T4_LENGTH_1200_B4 = 0,
00156     /* North American letter is 279.4mm long */
00157     T4_LENGTH_STANDARD_US_LETTER = 1075,
00158     T4_LENGTH_FINE_US_LETTER = 2151,
00159     T4_LENGTH_300_US_LETTER = 0,
00160     T4_LENGTH_SUPERFINE_US_LETTER = 4302,
00161     T4_LENGTH_600_US_LETTER = 0,
00162     T4_LENGTH_800_US_LETTER = 0,
00163     T4_LENGTH_1200_US_LETTER = 0,
00164     /* North American legal is 355.6mm long */
00165     T4_LENGTH_STANDARD_US_LEGAL = 1369,
00166     T4_LENGTH_FINE_US_LEGAL = 2738,
00167     T4_LENGTH_300_US_LEGAL = 0,
00168     T4_LENGTH_SUPERFINE_US_LEGAL = 5476,
00169     T4_LENGTH_600_US_LEGAL = 0,
00170     T4_LENGTH_800_US_LEGAL = 0,
00171     T4_LENGTH_1200_US_LEGAL = 0
00172 } t4_image_length_t;
00173 
00174 /*!
00175     T.4 FAX compression/decompression descriptor. This defines the working state
00176     for a single instance of a T.4 FAX compression or decompression channel.
00177 */
00178 typedef struct t4_state_s t4_state_t;
00179 
00180 /*!
00181     T.4 FAX compression/decompression statistics.
00182 */
00183 typedef struct
00184 {
00185     /*! \brief The number of pages transferred so far. */
00186     int pages_transferred;
00187     /*! \brief The number of pages in the file (<0 if unknown). */
00188     int pages_in_file;
00189     /*! \brief The number of horizontal pixels in the most recent page. */
00190     int width;
00191     /*! \brief The number of vertical pixels in the most recent page. */
00192     int length;
00193     /*! \brief The number of bad pixel rows in the most recent page. */
00194     int bad_rows;
00195     /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
00196     int longest_bad_row_run;
00197     /*! \brief The horizontal resolution of the page in pixels per metre */
00198     int x_resolution;
00199     /*! \brief The vertical resolution of the page in pixels per metre */
00200     int y_resolution;
00201     /*! \brief The type of compression used between the FAX machines */
00202     int encoding;
00203     /*! \brief The size of the image on the line, in bytes */
00204     int line_image_size;
00205 } t4_stats_t;
00206     
00207 #if defined(__cplusplus)
00208 extern "C" {
00209 #endif
00210 
00211 /*! \brief Prepare for reception of a document.
00212     \param s The T.4 context.
00213     \param file The name of the file to be received.
00214     \param output_encoding The output encoding.
00215     \return A pointer to the context, or NULL if there was a problem. */
00216 SPAN_DECLARE(t4_state_t *) t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
00217 
00218 /*! \brief Prepare to receive the next page of the current document.
00219     \param s The T.4 context.
00220     \return zero for success, -1 for failure. */
00221 SPAN_DECLARE(int) t4_rx_start_page(t4_state_t *s);
00222 
00223 /*! \brief Put a bit of the current document page.
00224     \param s The T.4 context.
00225     \param bit The data bit.
00226     \return TRUE when the bit ends the document page, otherwise FALSE. */
00227 SPAN_DECLARE(int) t4_rx_put_bit(t4_state_t *s, int bit);
00228 
00229 /*! \brief Put a byte of the current document page.
00230     \param s The T.4 context.
00231     \param byte The data byte.
00232     \return TRUE when the byte ends the document page, otherwise FALSE. */
00233 SPAN_DECLARE(int) t4_rx_put_byte(t4_state_t *s, uint8_t byte);
00234 
00235 /*! \brief Put a byte of the current document page.
00236     \param s The T.4 context.
00237     \param buf The buffer containing the chunk.
00238     \param len The length of the chunk.
00239     \return TRUE when the byte ends the document page, otherwise FALSE. */
00240 SPAN_DECLARE(int) t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len);
00241 
00242 /*! \brief Complete the reception of a page.
00243     \param s The T.4 receive context.
00244     \return 0 for success, otherwise -1. */
00245 SPAN_DECLARE(int) t4_rx_end_page(t4_state_t *s);
00246 
00247 /*! \brief End reception of a document. Tidy up and close the file.
00248            This should be used to end T.4 reception started with
00249            t4_rx_init.
00250     \param s The T.4 receive context.
00251     \return 0 for success, otherwise -1. */
00252 SPAN_DECLARE(int) t4_rx_release(t4_state_t *s);
00253 
00254 /*! \brief End reception of a document. Tidy up, close the file and
00255            free the context. This should be used to end T.4 reception
00256            started with t4_rx_init.
00257     \param s The T.4 receive context.
00258     \return 0 for success, otherwise -1. */
00259 SPAN_DECLARE(int) t4_rx_free(t4_state_t *s);
00260 
00261 /*! \brief Set the row write handler for a T.4 receive context.
00262     \param s The T.4 receive context.
00263     \param handler A pointer to the handler routine.
00264     \param user_data An opaque pointer passed to the handler routine.
00265     \return 0 for success, otherwise -1. */
00266 SPAN_DECLARE(int) t4_rx_set_row_write_handler(t4_state_t *s, t4_row_write_handler_t handler, void *user_data);
00267 
00268 /*! \brief Set the encoding for the received data.
00269     \param s The T.4 context.
00270     \param encoding The encoding. */
00271 SPAN_DECLARE(void) t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00272 
00273 /*! \brief Set the expected width of the received image, in pixel columns.
00274     \param s The T.4 context.
00275     \param width The number of pixels across the image. */
00276 SPAN_DECLARE(void) t4_rx_set_image_width(t4_state_t *s, int width);
00277 
00278 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00279     \param s The T.4 context.
00280     \param resolution The resolution, in pixels per metre. */
00281 SPAN_DECLARE(void) t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00282 
00283 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00284     \param s The T.4 context.
00285     \param resolution The resolution, in pixels per metre. */
00286 SPAN_DECLARE(void) t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00287 
00288 /*! \brief Set the DCS information of the fax, for inclusion in the file.
00289     \param s The T.4 context.
00290     \param dcs The DCS information, formatted as an ASCII string. */
00291 SPAN_DECLARE(void) t4_rx_set_dcs(t4_state_t *s, const char *dcs);
00292 
00293 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00294     \param s The T.4 context.
00295     \param sub_address The sub-address string. */
00296 SPAN_DECLARE(void) t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00297 
00298 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00299     \param s The T.4 context.
00300     \param ident The identity string. */
00301 SPAN_DECLARE(void) t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00302 
00303 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00304     \param s The T.4 context.
00305     \param vendor The vendor string, or NULL. */
00306 SPAN_DECLARE(void) t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00307 
00308 /*! \brief Set the model of the remote machine, for inclusion in the file.
00309     \param s The T.4 context.
00310     \param model The model string, or NULL. */
00311 SPAN_DECLARE(void) t4_rx_set_model(t4_state_t *s, const char *model);
00312 
00313 /*! \brief Prepare for transmission of a document.
00314     \param s The T.4 context.
00315     \param file The name of the file to be sent.
00316     \param start_page The first page to send. -1 for no restriction.
00317     \param stop_page The last page to send. -1 for no restriction.
00318     \return A pointer to the context, or NULL if there was a problem. */
00319 SPAN_DECLARE(t4_state_t *) t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00320 
00321 /*! \brief Prepare to send the next page of the current document.
00322     \param s The T.4 context.
00323     \return zero for success, -1 for failure. */
00324 SPAN_DECLARE(int) t4_tx_start_page(t4_state_t *s);
00325 
00326 /*! \brief Prepare the current page for a resend.
00327     \param s The T.4 context.
00328     \return zero for success, -1 for failure. */
00329 SPAN_DECLARE(int) t4_tx_restart_page(t4_state_t *s);
00330 
00331 /*! \brief Check for the existance of the next page, and whether its format is like the
00332     current one. This information can be needed before it is determined that the current
00333     page is finished with.
00334     \param s The T.4 context.
00335     \return 0 for next page found with the same format as the current page.
00336             1 for next page found with different format from the current page.
00337             -1 for no page found, or file failure. */
00338 SPAN_DECLARE(int) t4_tx_next_page_has_different_format(t4_state_t *s);
00339 
00340 /*! \brief Complete the sending of a page.
00341     \param s The T.4 context.
00342     \return zero for success, -1 for failure. */
00343 SPAN_DECLARE(int) t4_tx_end_page(t4_state_t *s);
00344 
00345 /*! \brief Get the next bit of the current document page. The document will
00346            be padded for the current minimum scan line time. If the
00347            file does not contain an RTC (return to control) code at
00348            the end of the page, one will be added where appropriate.
00349     \param s The T.4 context.
00350     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00351             set (i.e. the returned value is 2 or 3). */
00352 SPAN_DECLARE(int) t4_tx_get_bit(t4_state_t *s);
00353 
00354 /*! \brief Get the next byte of the current document page. The document will
00355            be padded for the current minimum scan line time. If the
00356            file does not contain an RTC (return to control) code at
00357            the end of the page, one will be added where appropriate.
00358     \param s The T.4 context.
00359     \return The next byte. For the last byte of data, bit 8 is
00360             set. In this case, one or more bits of the byte may be padded with
00361             zeros, to complete the byte. */
00362 SPAN_DECLARE(int) t4_tx_get_byte(t4_state_t *s);
00363 
00364 /*! \brief Get the next chunk of the current document page. The document will
00365            be padded for the current minimum scan line time. If the
00366            file does not contain an RTC (return to control) code at
00367            the end of the page, one will be added where appropriate.
00368     \param s The T.4 context.
00369     \param buf The buffer into which the chunk is to written.
00370     \param max_len The maximum length of the chunk.
00371     \return The actual length of the chunk. If this is less than max_len it 
00372             indicates that the end of the document has been reached. */
00373 SPAN_DECLARE(int) t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00374 
00375 /*! \brief Return the next bit of the current document page, without actually
00376            moving forward in the buffer. The document will be padded for the
00377            current minimum scan line time. If the file does not contain an
00378            RTC (return to control) code at the end of the page, one will be
00379            added.
00380     \param s The T.4 context.
00381     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00382             set (i.e. the returned value is 2 or 3). */
00383 SPAN_DECLARE(int) t4_tx_check_bit(t4_state_t *s);
00384 
00385 /*! \brief End the transmission of a document. Tidy up and close the file.
00386            This should be used to end T.4 transmission started with t4_tx_init.
00387     \param s The T.4 context.
00388     \return 0 for success, otherwise -1. */
00389 SPAN_DECLARE(int) t4_tx_release(t4_state_t *s);
00390 
00391 /*! \brief End the transmission of a document. Tidy up, close the file and
00392            free the context. This should be used to end T.4 transmission
00393            started with t4_tx_init.
00394     \param s The T.4 context.
00395     \return 0 for success, otherwise -1. */
00396 SPAN_DECLARE(int) t4_tx_free(t4_state_t *s);
00397 
00398 /*! \brief Set the encoding for the encoded data.
00399     \param s The T.4 context.
00400     \param encoding The encoding. */
00401 SPAN_DECLARE(void) t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00402 
00403 /*! \brief Set the minimum number of encoded bits per row. This allows the
00404            makes the encoding process to be set to comply with the minimum row
00405            time specified by a remote receiving machine.
00406     \param s The T.4 context.
00407     \param bits The minimum number of bits per row. */
00408 SPAN_DECLARE(void) t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00409 
00410 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00411     \param s The T.4 context.
00412     \param ident The identity string. */
00413 SPAN_DECLARE(void) t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00414 
00415 /*! Set the info field, included in the header line included in each page of an encoded
00416     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00417     are automatically included in the header. If the header info is set to NULL or a zero
00418     length string, no header lines will be added to the encoded FAX.
00419     \brief Set the header info.
00420     \param s The T.4 context.
00421     \param info A string, of up to 50 bytes, which will form the info field. */
00422 SPAN_DECLARE(void) t4_tx_set_header_info(t4_state_t *s, const char *info);
00423 
00424 /*! \brief Set the row read handler for a T.4 transmit context.
00425     \param s The T.4 transmit context.
00426     \param handler A pointer to the handler routine.
00427     \param user_data An opaque pointer passed to the handler routine.
00428     \return 0 for success, otherwise -1. */
00429 SPAN_DECLARE(int) t4_tx_set_row_read_handler(t4_state_t *s, t4_row_read_handler_t handler, void *user_data);
00430 
00431 /*! \brief Get the row-to-row (y) resolution of the current page.
00432     \param s The T.4 context.
00433     \return The resolution, in pixels per metre. */
00434 SPAN_DECLARE(int) t4_tx_get_y_resolution(t4_state_t *s);
00435 
00436 /*! \brief Get the column-to-column (x) resolution of the current page.
00437     \param s The T.4 context.
00438     \return The resolution, in pixels per metre. */
00439 SPAN_DECLARE(int) t4_tx_get_x_resolution(t4_state_t *s);
00440 
00441 /*! \brief Get the width of the current page, in pixel columns.
00442     \param s The T.4 context.
00443     \return The number of columns. */
00444 SPAN_DECLARE(int) t4_tx_get_image_width(t4_state_t *s);
00445 
00446 /*! \brief Get the number of pages in the file.
00447     \param s The T.4 context.
00448     \return The number of pages, or -1 if there is an error. */
00449 SPAN_DECLARE(int) t4_tx_get_pages_in_file(t4_state_t *s);
00450 
00451 /*! \brief Get the currnet page number in the file.
00452     \param s The T.4 context.
00453     \return The page number, or -1 if there is an error. */
00454 SPAN_DECLARE(int) t4_tx_get_current_page_in_file(t4_state_t *s);
00455 
00456 /*! Get the current image transfer statistics. 
00457     \brief Get the current transfer statistics.
00458     \param s The T.4 context.
00459     \param t A pointer to a statistics structure. */
00460 SPAN_DECLARE(void) t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00461 
00462 /*! Get the short text name of an encoding format. 
00463     \brief Get the short text name of an encoding format.
00464     \param encoding The encoding type.
00465     \return A pointer to the string. */
00466 SPAN_DECLARE(const char *) t4_encoding_to_str(int encoding);
00467 
00468 #if defined(__cplusplus)
00469 }
00470 #endif
00471 
00472 #endif
00473 /*- End of file ------------------------------------------------------------*/

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