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 General Public License version 2, as
00014  * 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 General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU General Public License
00022  * 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 1.33 2007/05/28 14:05:39 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 #define T4_COMPRESSION_ITU_T4_1D    1
00045 #define T4_COMPRESSION_ITU_T4_2D    2
00046 #define T4_COMPRESSION_ITU_T6       3
00047 
00048 #define T4_X_RESOLUTION_R4          4019
00049 #define T4_X_RESOLUTION_R8          8037
00050 #define T4_X_RESOLUTION_R16         16074
00051 
00052 #define T4_Y_RESOLUTION_STANDARD    3850
00053 #define T4_Y_RESOLUTION_FINE        7700
00054 #define T4_Y_RESOLUTION_SUPERFINE   15400
00055 
00056 /*!
00057     T.4 FAX compression/decompression descriptor. This defines the working state
00058     for a single instance of a T.4 FAX compression or decompression channel.
00059 */
00060 typedef struct
00061 {
00062     /* "Background" information about the FAX, which can be stored in a TIFF file. */
00063     /*! \brief The vendor of the machine which produced the TIFF file. */ 
00064     const char      *vendor;
00065     /*! \brief The model of machine which produced the TIFF file. */ 
00066     const char      *model;
00067     /*! \brief The local ident string. */ 
00068     const char      *local_ident;
00069     /*! \brief The remote end's ident string. */ 
00070     const char      *far_ident;
00071     /*! \brief The FAX sub-address. */ 
00072     const char      *sub_address;
00073     /*! \brief The text which will be used in FAX page header. No text results
00074                in no header line. */
00075     const char      *header_info;
00076 
00077     /*! \brief The type of compression used between the FAX machines. */
00078     int             line_encoding;
00079     /*! \brief The minimum number of bits per scan row. This is a timing thing
00080                for hardware FAX machines. */
00081     int             min_scan_line_bits;
00082     
00083     int             output_compression;
00084     int             output_t4_options;
00085 
00086     time_t          page_start_time;
00087 
00088     int             bytes_per_row;
00089     int             image_size;
00090     int             image_buffer_size;
00091     uint8_t         *image_buffer;
00092 
00093     TIFF            *tiff_file;
00094     const char      *file;
00095     int             start_page;
00096     int             stop_page;
00097 
00098     int             pages_transferred;
00099     int             pages_in_file;
00100     /*! Column-to-column (X) resolution in pixels per metre. */
00101     int             x_resolution;
00102     /*! Row-to-row (Y) resolution in pixels per metre. */
00103     int             y_resolution;
00104     /*! Width of the current page, in pixels. */
00105     int             image_width;
00106     /*! Current pixel row number. */
00107     int             row;
00108     /*! Total pixel rows in the current page. */
00109     int             image_length;
00110     /*! The current number of consecutive bad rows. */
00111     int             curr_bad_row_run;
00112     /*! The longest run of consecutive bad rows seen in the current page. */
00113     int             longest_bad_row_run;
00114     /*! The total number of bad rows in the current page. */
00115     int             bad_rows;
00116 
00117     /* Decode state */
00118     uint32_t        bits_to_date;
00119     int             bits;
00120 
00121     /*! \brief This variable is set if we are treating the current row as a 2D encoded
00122                one. */
00123     int             row_is_2d;
00124     int             its_black;
00125     int             row_len;
00126     /*! \brief This variable is used to record the fact we have seen at least one EOL
00127                since we started decoding. We will not try to interpret the received
00128                data as an image until we have seen the first EOL. */
00129     int             first_eol_seen;
00130     /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
00131                reaches six, this is the end of the image. */
00132     int             consecutive_eols;
00133 
00134     /*! \brief B&W runs for reference line */
00135     uint32_t        *ref_runs;
00136     /*! \brief B&W runs for current line */
00137     uint32_t        *cur_runs;
00138 
00139     uint32_t        *pa;
00140     uint32_t        *pb;
00141     int             a0;
00142     int             b1;
00143     /*! \brief The length of the current run of black or white. */
00144     int             run_length;
00145     int             black_white;
00146 
00147     uint32_t        data;
00148     int             bit;
00149 
00150     /*! \brief A point into the image buffer indicating where the last row begins */
00151     int             last_row_starts_at;
00152     /*! \brief A point into the image buffer indicating where the current row begins */
00153     int             row_starts_at;
00154     
00155     /* Encode state */
00156 
00157     /*! Pointer to the buffer for the current pixel row. */
00158     uint8_t         *row_buf;
00159     
00160     int             bit_pos;
00161     int             bit_ptr;
00162 
00163     /*! \brief The reference pixel row for 2D encoding. */
00164     uint8_t         *ref_row_buf;
00165     /*! \brief The maximum contiguous rows that will be 2D encoded. */
00166     int             max_rows_to_next_1d_row;
00167     /*! \brief Number of rows left that can be 2D encoded, before a 1D encoded row
00168                must be used. */
00169     int             rows_to_next_1d_row;
00170     /*! \brief The minimum number of encoded bits per row. */
00171     int             min_row_bits;
00172     /*! \brief The current number of bits in the current encoded row. */
00173     int             row_bits;
00174 
00175     /*! \brief Error and flow logging control */
00176     logging_state_t logging;
00177 } t4_state_t;
00178 
00179 /*!
00180     T.4 FAX compression/decompression statistics.
00181 */
00182 typedef struct
00183 {
00184     /*! \brief The number of pages transferred so far. */
00185     int pages_transferred;
00186     /*! \brief The number of pages in the file (<0 if unknown). */
00187     int pages_in_file;
00188     /*! \brief The number of horizontal pixels in the most recent page. */
00189     int width;
00190     /*! \brief The number of vertical pixels in the most recent page. */
00191     int length;
00192     /*! \brief The number of bad pixel rows in the most recent page. */
00193     int bad_rows;
00194     /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
00195     int longest_bad_row_run;
00196     /*! \brief The horizontal resolution of the page in pixels per metre */
00197     int x_resolution;
00198     /*! \brief The vertical resolution of the page in pixels per metre */
00199     int y_resolution;
00200     /*! \brief The type of compression used between the FAX machines */
00201     int encoding;
00202     /*! \brief The size of the image, in bytes */
00203     int image_size;
00204 } t4_stats_t;
00205     
00206 #if defined(__cplusplus)
00207 extern "C" {
00208 #endif
00209 
00210 /*! \brief Allocate a T.4 transmit handling context, and
00211            initialise it.
00212     \param file The name of the file to be received.
00213     \param output_encoding The output encoding.
00214     \return The T.4 context, or NULL. */
00215 t4_state_t *t4_rx_create(const char *file, int output_encoding);
00216 
00217 /*! \brief Prepare for reception of a document.
00218     \param s The T.4 context.
00219     \param file The name of the file to be received.
00220     \param output_encoding The output encoding.
00221     \return 0 for success, otherwise -1. */
00222 int t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
00223 
00224 /*! \brief Prepare to receive the next page of the current document.
00225     \param s The T.4 context.
00226     \return zero for success, -1 for failure. */
00227 int t4_rx_start_page(t4_state_t *s);
00228 
00229 /*! \brief Put a bit of the current document page.
00230     \param s The T.4 context.
00231     \param bit The data bit.
00232     \return TRUE when the bit ends the document page, otherwise FALSE. */
00233 int t4_rx_put_bit(t4_state_t *s, int bit);
00234 
00235 /*! \brief Put a byte of the current document page.
00236     \param s The T.4 context.
00237     \param byte The data byte.
00238     \return TRUE when the byte ends the document page, otherwise FALSE. */
00239 int t4_rx_put_byte(t4_state_t *s, uint8_t byte);
00240 
00241 /*! \brief Put a byte of the current document page.
00242     \param s The T.4 context.
00243     \param buf The buffer containing the chunk.
00244     \param len The length of the chunk.
00245     \return TRUE when the byte ends the document page, otherwise FALSE. */
00246 int t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len);
00247 
00248 /*! \brief Complete the reception of a page.
00249     \param s The T.4 receive context.
00250     \return 0 for success, otherwise -1. */
00251 int t4_rx_end_page(t4_state_t *s);
00252 
00253 /*! \brief End reception of a document. Tidy up, close the file and
00254            free the context. This should be used to end T.4 reception
00255            started with t4_rx_create.
00256     \param s The T.4 receive context.
00257     \return 0 for success, otherwise -1. */
00258 int t4_rx_delete(t4_state_t *s);
00259 
00260 /*! \brief End reception of a document. Tidy up and close the file.
00261            This should be used to end T.4 reception started with
00262            t4_rx_init.
00263     \param s The T.4 context.
00264     \return 0 for success, otherwise -1. */
00265 int t4_rx_end(t4_state_t *s);
00266 
00267 /*! \brief Set the encoding for the received data.
00268     \param s The T.4 context.
00269     \param encoding The encoding. */
00270 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00271 
00272 /*! \brief Set the expected width of the received image, in pixel columns.
00273     \param s The T.4 context.
00274     \param columns The number of pixels across the image. */
00275 void t4_rx_set_image_width(t4_state_t *s, int width);
00276 
00277 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00278     \param s The T.4 context.
00279     \param resolution The resolution, in pixels per metre. */
00280 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00281 
00282 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00283     \param s The T.4 context.
00284     \param resolution The resolution, in pixels per metre. */
00285 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00286 
00287 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00288     \param s The T.4 context.
00289     \param sub_address The sub-address string. */
00290 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00291 
00292 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00293     \param s The T.4 context.
00294     \param ident The identity string. */
00295 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00296 
00297 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00298     \param s The T.4 context.
00299     \param vendor The vendor string, or NULL. */
00300 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00301 
00302 /*! \brief Set the model of the remote machine, for inclusion in the file.
00303     \param s The T.4 context.
00304     \param model The model string, or NULL. */
00305 void t4_rx_set_model(t4_state_t *s, const char *model);
00306 
00307 /*! \brief Allocate a T.4 receive handling context, and
00308            initialise it.
00309     \param s The T.4 context.
00310     \param file The name of the file to be sent.
00311     \return 0 for success, otherwise -1. */
00312 t4_state_t *t4_tx_create(const char *file, int start_page, int stop_page);
00313 
00314 /*! \brief Prepare for transmission of a document.
00315     \param s The T.4 context.
00316     \param file The name of the file to be sent.
00317     \param start_page The first page to send. -1 for no restriction.
00318     \param stop_page The last page to send. -1 for no restriction.
00319     \return The T.4 context, or NULL. */
00320 int t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00321 
00322 /*! \brief Prepare to send the next page of the current document.
00323     \param s The T.4 context.
00324     \return zero for success, -1 for failure. */
00325 int t4_tx_start_page(t4_state_t *s);
00326 
00327 /*! \brief Prepare the current page for a resend.
00328     \param s The T.4 context.
00329     \return zero for success, -1 for failure. */
00330 int t4_tx_restart_page(t4_state_t *s);
00331 
00332 /*! \brief Check for the existance of the next page. This information can
00333     be needed before it is determined that the current page is finished with.
00334     \param s The T.4 context.
00335     \return zero for next page found, -1 for failure. */
00336 int t4_tx_more_pages(t4_state_t *s);
00337 
00338 /*! \brief Complete the sending of a page.
00339     \param s The T.4 context.
00340     \return zero for success, -1 for failure. */
00341 int t4_tx_end_page(t4_state_t *s);
00342 
00343 /*! \brief Get the next bit of the current document page. The document will
00344            be padded for the current minimum scan line time. If the
00345            file does not contain an RTC (return to control) code at
00346            the end of the page, one will be added where appropriate.
00347     \param s The T.4 context.
00348     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00349             set (i.e. the returned value is 2 or 3). */
00350 int t4_tx_get_bit(t4_state_t *s);
00351 
00352 /*! \brief Get the next byte of the current document page. The document will
00353            be padded for the current minimum scan line time. If the
00354            file does not contain an RTC (return to control) code at
00355            the end of the page, one will be added where appropriate.
00356     \param s The T.4 context.
00357     \return The next byte. For the last byte of data, bit 8 is
00358             set. In this case, one or more bits of the byte may be padded with
00359             zeros, to complete the byte. */
00360 int t4_tx_get_byte(t4_state_t *s);
00361 
00362 /*! \brief Get the next chunk of the current document page. The document will
00363            be padded for the current minimum scan line time. If the
00364            file does not contain an RTC (return to control) code at
00365            the end of the page, one will be added where appropriate.
00366     \param s The T.4 context.
00367     \param buf The buffer into which the chunk is to written.
00368     \param max_len The maximum length of the chunk.
00369     \return The actual length of the chunk. If this is less than max_len it 
00370             indicates that the end of the document has been reached. */
00371 int t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00372 
00373 /*! \brief Return the next bit of the current document page, without actually
00374            moving forward in the buffer. The document will be padded for the
00375            current minimum scan line time. If the file does not contain an
00376            RTC (return to control) code at the end of the page, one will be
00377            added.
00378     \param s The T.4 context.
00379     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00380             set (i.e. the returned value is 2 or 3). */
00381 int t4_tx_check_bit(t4_state_t *s);
00382 
00383 /*! \brief End the transmission of a document. Tidy up, close the file and
00384            free the context. This should be used to end T.4 transmission
00385            started with t4_tx_create.
00386     \param s The T.4 context.
00387     \return 0 for success, otherwise -1. */
00388 int t4_tx_delete(t4_state_t *s);
00389 
00390 /*! \brief End the transmission of a document. Tidy up and close the file.
00391            This should be used to end T.4 transmission started with t4_tx_init.
00392     \param s The T.4 context.
00393     \return 0 for success, otherwise -1. */
00394 int t4_tx_end(t4_state_t *s);
00395 
00396 /*! \brief Set the encoding for the encoded data.
00397     \param s The T.4 context.
00398     \param encoding The encoding. */
00399 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00400 
00401 /*! \brief Set the minimum number of encoded bits per row. This allows the
00402            makes the encoding process to be set to comply with the minimum row
00403            time specified by a remote receiving machine.
00404     \param s The T.4 context.
00405     \param bits The minimum number of bits per row. */
00406 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00407 
00408 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00409     \param s The T.4 context.
00410     \param ident The identity string. */
00411 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00412 
00413 /*! Set the info field, included in the header line included in each page of an encoded
00414     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00415     are automatically included in the header. If the header info is set to NULL or a zero
00416     length string, no header lines will be added to the encoded FAX.
00417     \brief Set the header info.
00418     \param s The T.4 context.
00419     \param info A string, of up to 50 bytes, which will form the info field. */
00420 void t4_tx_set_header_info(t4_state_t *s, const char *info);
00421 
00422 /*! \brief Get the row-to-row (y) resolution of the current page.
00423     \param s The T.4 context.
00424     \return The resolution, in pixels per metre. */
00425 int t4_tx_get_y_resolution(t4_state_t *s);
00426 
00427 /*! \brief Get the column-to-column (x) resolution of the current page.
00428     \param s The T.4 context.
00429     \return The resolution, in pixels per metre. */
00430 int t4_tx_get_x_resolution(t4_state_t *s);
00431 
00432 /*! \brief Get the width of the current page, in pixel columns.
00433     \param s The T.4 context.
00434     \return The number of columns. */
00435 int t4_tx_get_image_width(t4_state_t *s);
00436 
00437 /*! \brief Get the number of pages in the file.
00438     \param s The T.4 context.
00439     \return The number of pages, or -1 if there is an error. */
00440 int t4_tx_get_pages_in_file(t4_state_t *s);
00441 
00442 /*! Get the current image transfer statistics. 
00443     \brief Get the current transfer statistics.
00444     \param s The T.4 context.
00445     \param t A pointer to a statistics structure. */
00446 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00447 
00448 /*! Get the short text name of an encoding format. 
00449     \brief Get the short text name of an encoding format.
00450     \param encoding The encoding type.
00451     \return A pointer to the string. */
00452 const char *t4_encoding_to_str(int encoding);
00453 
00454 #if defined(__cplusplus)
00455 }
00456 #endif
00457 
00458 #endif
00459 /*- End of file ------------------------------------------------------------*/

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