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 1.53 2008/10/13 13:14:01 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 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 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 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 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 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 int t4_rx_end_page(t4_state_t *s);
00246 
00247 /*! \brief End reception of a document. Tidy up, close the file and
00248            free the context. This should be used to end T.4 reception
00249            started with t4_rx_init.
00250     \param s The T.4 receive context.
00251     \return 0 for success, otherwise -1. */
00252 int t4_rx_delete(t4_state_t *s);
00253 
00254 /*! \brief End reception of a document. Tidy up and close the file.
00255            This should be used to end T.4 reception started with
00256            t4_rx_init.
00257     \param s The T.4 context.
00258     \return 0 for success, otherwise -1. */
00259 int t4_rx_end(t4_state_t *s);
00260 
00261 int t4_rx_set_row_write_handler(t4_state_t *s, t4_row_write_handler_t handler, void *user_data);
00262 
00263 /*! \brief Set the encoding for the received data.
00264     \param s The T.4 context.
00265     \param encoding The encoding. */
00266 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00267 
00268 /*! \brief Set the expected width of the received image, in pixel columns.
00269     \param s The T.4 context.
00270     \param width The number of pixels across the image. */
00271 void t4_rx_set_image_width(t4_state_t *s, int width);
00272 
00273 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00274     \param s The T.4 context.
00275     \param resolution The resolution, in pixels per metre. */
00276 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00277 
00278 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00279     \param s The T.4 context.
00280     \param resolution The resolution, in pixels per metre. */
00281 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00282 
00283 /*! \brief Set the DCS information of the fax, for inclusion in the file.
00284     \param s The T.4 context.
00285     \param dcs The DCS information, formatted as an ASCII string. */
00286 void t4_rx_set_dcs(t4_state_t *s, const char *dcs);
00287 
00288 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00289     \param s The T.4 context.
00290     \param sub_address The sub-address string. */
00291 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00292 
00293 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00294     \param s The T.4 context.
00295     \param ident The identity string. */
00296 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00297 
00298 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00299     \param s The T.4 context.
00300     \param vendor The vendor string, or NULL. */
00301 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00302 
00303 /*! \brief Set the model of the remote machine, for inclusion in the file.
00304     \param s The T.4 context.
00305     \param model The model string, or NULL. */
00306 void t4_rx_set_model(t4_state_t *s, const char *model);
00307 
00308 /*! \brief Prepare for transmission of a document.
00309     \param s The T.4 context.
00310     \param file The name of the file to be sent.
00311     \param start_page The first page to send. -1 for no restriction.
00312     \param stop_page The last page to send. -1 for no restriction.
00313     \return A pointer to the context, or NULL if there was a problem. */
00314 t4_state_t *t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00315 
00316 /*! \brief Prepare to send the next page of the current document.
00317     \param s The T.4 context.
00318     \return zero for success, -1 for failure. */
00319 int t4_tx_start_page(t4_state_t *s);
00320 
00321 /*! \brief Prepare the current page for a resend.
00322     \param s The T.4 context.
00323     \return zero for success, -1 for failure. */
00324 int t4_tx_restart_page(t4_state_t *s);
00325 
00326 /*! \brief Check for the existance of the next page. This information can
00327     be needed before it is determined that the current page is finished with.
00328     \param s The T.4 context.
00329     \return zero for next page found, -1 for failure. */
00330 int t4_tx_more_pages(t4_state_t *s);
00331 
00332 /*! \brief Complete the sending of a page.
00333     \param s The T.4 context.
00334     \return zero for success, -1 for failure. */
00335 int t4_tx_end_page(t4_state_t *s);
00336 
00337 /*! \brief Get the next bit of the current document page. The document will
00338            be padded for the current minimum scan line time. If the
00339            file does not contain an RTC (return to control) code at
00340            the end of the page, one will be added where appropriate.
00341     \param s The T.4 context.
00342     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00343             set (i.e. the returned value is 2 or 3). */
00344 int t4_tx_get_bit(t4_state_t *s);
00345 
00346 /*! \brief Get the next byte of the current document page. The document will
00347            be padded for the current minimum scan line time. If the
00348            file does not contain an RTC (return to control) code at
00349            the end of the page, one will be added where appropriate.
00350     \param s The T.4 context.
00351     \return The next byte. For the last byte of data, bit 8 is
00352             set. In this case, one or more bits of the byte may be padded with
00353             zeros, to complete the byte. */
00354 int t4_tx_get_byte(t4_state_t *s);
00355 
00356 /*! \brief Get the next chunk of the current document page. The document will
00357            be padded for the current minimum scan line time. If the
00358            file does not contain an RTC (return to control) code at
00359            the end of the page, one will be added where appropriate.
00360     \param s The T.4 context.
00361     \param buf The buffer into which the chunk is to written.
00362     \param max_len The maximum length of the chunk.
00363     \return The actual length of the chunk. If this is less than max_len it 
00364             indicates that the end of the document has been reached. */
00365 int t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00366 
00367 /*! \brief Return the next bit of the current document page, without actually
00368            moving forward in the buffer. The document will be padded for the
00369            current minimum scan line time. If the file does not contain an
00370            RTC (return to control) code at the end of the page, one will be
00371            added.
00372     \param s The T.4 context.
00373     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00374             set (i.e. the returned value is 2 or 3). */
00375 int t4_tx_check_bit(t4_state_t *s);
00376 
00377 /*! \brief End the transmission of a document. Tidy up, close the file and
00378            free the context. This should be used to end T.4 transmission
00379            started with t4_tx_init.
00380     \param s The T.4 context.
00381     \return 0 for success, otherwise -1. */
00382 int t4_tx_delete(t4_state_t *s);
00383 
00384 /*! \brief End the transmission of a document. Tidy up and close the file.
00385            This should be used to end T.4 transmission started with t4_tx_init.
00386     \param s The T.4 context.
00387     \return 0 for success, otherwise -1. */
00388 int t4_tx_end(t4_state_t *s);
00389 
00390 /*! \brief Set the encoding for the encoded data.
00391     \param s The T.4 context.
00392     \param encoding The encoding. */
00393 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00394 
00395 /*! \brief Set the minimum number of encoded bits per row. This allows the
00396            makes the encoding process to be set to comply with the minimum row
00397            time specified by a remote receiving machine.
00398     \param s The T.4 context.
00399     \param bits The minimum number of bits per row. */
00400 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00401 
00402 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00403     \param s The T.4 context.
00404     \param ident The identity string. */
00405 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00406 
00407 /*! Set the info field, included in the header line included in each page of an encoded
00408     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00409     are automatically included in the header. If the header info is set to NULL or a zero
00410     length string, no header lines will be added to the encoded FAX.
00411     \brief Set the header info.
00412     \param s The T.4 context.
00413     \param info A string, of up to 50 bytes, which will form the info field. */
00414 void t4_tx_set_header_info(t4_state_t *s, const char *info);
00415 
00416 int t4_tx_set_row_read_handler(t4_state_t *s, t4_row_read_handler_t handler, void *user_data);
00417 
00418 /*! \brief Get the row-to-row (y) resolution of the current page.
00419     \param s The T.4 context.
00420     \return The resolution, in pixels per metre. */
00421 int t4_tx_get_y_resolution(t4_state_t *s);
00422 
00423 /*! \brief Get the column-to-column (x) resolution of the current page.
00424     \param s The T.4 context.
00425     \return The resolution, in pixels per metre. */
00426 int t4_tx_get_x_resolution(t4_state_t *s);
00427 
00428 /*! \brief Get the width of the current page, in pixel columns.
00429     \param s The T.4 context.
00430     \return The number of columns. */
00431 int t4_tx_get_image_width(t4_state_t *s);
00432 
00433 /*! \brief Get the number of pages in the file.
00434     \param s The T.4 context.
00435     \return The number of pages, or -1 if there is an error. */
00436 int t4_tx_get_pages_in_file(t4_state_t *s);
00437 
00438 /*! Get the current image transfer statistics. 
00439     \brief Get the current transfer statistics.
00440     \param s The T.4 context.
00441     \param t A pointer to a statistics structure. */
00442 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00443 
00444 /*! Get the short text name of an encoding format. 
00445     \brief Get the short text name of an encoding format.
00446     \param encoding The encoding type.
00447     \return A pointer to the string. */
00448 const char *t4_encoding_to_str(int encoding);
00449 
00450 #if defined(__cplusplus)
00451 }
00452 #endif
00453 
00454 #endif
00455 /*- End of file ------------------------------------------------------------*/

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