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 1.31 2007/04/05 19:20:50 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     /*! Column-to-column (X) resolution in pixels per metre. */
00100     int             x_resolution;
00101     /*! Row-to-row (Y) resolution in pixels per metre. */
00102     int             y_resolution;
00103     /*! Width of the current page, in pixels. */
00104     int             image_width;
00105     /*! Current pixel row number. */
00106     int             row;
00107     /*! Total pixel rows in the current page. */
00108     int             image_length;
00109     /*! The current number of consecutive bad rows. */
00110     int             curr_bad_row_run;
00111     /*! The longest run of consecutive bad rows seen in the current page. */
00112     int             longest_bad_row_run;
00113     /*! The total number of bad rows in the current page. */
00114     int             bad_rows;
00115 
00116     /* Decode state */
00117     uint32_t        bits_to_date;
00118     int             bits;
00119 
00120     /*! \brief This variable is set if we are treating the current row as a 2D encoded
00121                one. */
00122     int             row_is_2d;
00123     int             its_black;
00124     int             row_len;
00125     /*! \brief This variable is used to record the fact we have seen at least one EOL
00126                since we started decoding. We will not try to interpret the received
00127                data as an image until we have seen the first EOL. */
00128     int             first_eol_seen;
00129     /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
00130                reaches six, this is the end of the image. */
00131     int             consecutive_eols;
00132 
00133     /*! \brief B&W runs for reference line */
00134     uint32_t        *ref_runs;
00135     /*! \brief B&W runs for current line */
00136     uint32_t        *cur_runs;
00137 
00138     uint32_t        *pa;
00139     uint32_t        *pb;
00140     int             a0;
00141     int             b1;
00142     /*! \brief The length of the current run of black or white. */
00143     int             run_length;
00144     int             black_white;
00145 
00146     uint32_t        data;
00147     int             bit;
00148 
00149     /*! \brief A point into the image buffer indicating where the last row begins */
00150     int             last_row_starts_at;
00151     /*! \brief A point into the image buffer indicating where the current row begins */
00152     int             row_starts_at;
00153     
00154     /* Encode state */
00155 
00156     /*! Pointer to the buffer for the current pixel row. */
00157     uint8_t         *row_buf;
00158     
00159     int             bit_pos;
00160     int             bit_ptr;
00161 
00162     /*! \brief The reference pixel row for 2D encoding. */
00163     uint8_t         *ref_row_buf;
00164     /*! \brief The maximum contiguous rows that will be 2D encoded. */
00165     int             max_rows_to_next_1d_row;
00166     /*! \brief Number of rows left that can be 2D encoded, before a 1D encoded row
00167                must be used. */
00168     int             rows_to_next_1d_row;
00169     /*! \brief The minimum number of encoded bits per row. */
00170     int             min_row_bits;
00171     /*! \brief The current number of bits in the current encoded row. */
00172     int             row_bits;
00173 
00174     /*! \brief Error and flow logging control */
00175     logging_state_t logging;
00176 } t4_state_t;
00177 
00178 /*!
00179     T.4 FAX compression/decompression statistics.
00180 */
00181 typedef struct
00182 {
00183     /*! \brief The number of pages transferred so far. */
00184     int pages_transferred;
00185     /*! \brief The number of horizontal pixels in the most recent page. */
00186     int width;
00187     /*! \brief The number of vertical pixels in the most recent page. */
00188     int length;
00189     /*! \brief The number of bad pixel rows in the most recent page. */
00190     int bad_rows;
00191     /*! \brief The largest number of bad pixel rows in a block in the most recent page. */
00192     int longest_bad_row_run;
00193     /*! \brief The horizontal resolution of the page in pixels per metre */
00194     int x_resolution;
00195     /*! \brief The vertical resolution of the page in pixels per metre */
00196     int y_resolution;
00197     /*! \brief The type of compression used between the FAX machines */
00198     int encoding;
00199     /*! \brief The size of the image, in bytes */
00200     int image_size;
00201 } t4_stats_t;
00202     
00203 #ifdef __cplusplus
00204 extern "C" {
00205 #endif
00206 
00207 /*! \brief Allocate a T.4 transmit handling context, and
00208            initialise it.
00209     \param file The name of the file to be received.
00210     \param output_encoding The output encoding.
00211     \return The T.4 context, or NULL. */
00212 t4_state_t *t4_rx_create(const char *file, int output_encoding);
00213 
00214 /*! \brief Prepare for reception of a document.
00215     \param s The T.4 context.
00216     \param file The name of the file to be received.
00217     \param output_encoding The output encoding.
00218     \return 0 for success, otherwise -1. */
00219 int t4_rx_init(t4_state_t *s, const char *file, int output_encoding);
00220 
00221 /*! \brief Prepare to receive the next page of the current document.
00222     \param s The T.4 context.
00223     \return zero for success, -1 for failure. */
00224 int t4_rx_start_page(t4_state_t *s);
00225 
00226 /*! \brief Put a bit of the current document page.
00227     \param s The T.4 context.
00228     \param bit The data bit.
00229     \return TRUE when the bit ends the document page, otherwise FALSE. */
00230 int t4_rx_put_bit(t4_state_t *s, int bit);
00231 
00232 /*! \brief Put a byte of the current document page.
00233     \param s The T.4 context.
00234     \param byte The data byte.
00235     \return TRUE when the byte ends the document page, otherwise FALSE. */
00236 int t4_rx_put_byte(t4_state_t *s, uint8_t byte);
00237 
00238 /*! \brief Put a byte of the current document page.
00239     \param s The T.4 context.
00240     \param buf The buffer containing the chunk.
00241     \param len The length of the chunk.
00242     \return TRUE when the byte ends the document page, otherwise FALSE. */
00243 int t4_rx_put_chunk(t4_state_t *s, const uint8_t buf[], int len);
00244 
00245 /*! \brief Complete the reception of a page.
00246     \param s The T.4 receive context.
00247     \return 0 for success, otherwise -1. */
00248 int t4_rx_end_page(t4_state_t *s);
00249 
00250 /*! \brief End reception of a document. Tidy up, close the file and
00251            free the context. This should be used to end T.4 reception
00252            started with t4_rx_create.
00253     \param s The T.4 receive context.
00254     \return 0 for success, otherwise -1. */
00255 int t4_rx_delete(t4_state_t *s);
00256 
00257 /*! \brief End reception of a document. Tidy up and close the file.
00258            This should be used to end T.4 reception started with
00259            t4_rx_init.
00260     \param s The T.4 context.
00261     \return 0 for success, otherwise -1. */
00262 int t4_rx_end(t4_state_t *s);
00263 
00264 /*! \brief Set the encoding for the received data.
00265     \param s The T.4 context.
00266     \param encoding The encoding. */
00267 void t4_rx_set_rx_encoding(t4_state_t *s, int encoding);
00268 
00269 /*! \brief Set the expected width of the received image, in pixel columns.
00270     \param s The T.4 context.
00271     \param columns The number of pixels across the image. */
00272 void t4_rx_set_image_width(t4_state_t *s, int width);
00273 
00274 /*! \brief Set the row-to-row (y) resolution to expect for a received image.
00275     \param s The T.4 context.
00276     \param resolution The resolution, in pixels per metre. */
00277 void t4_rx_set_y_resolution(t4_state_t *s, int resolution);
00278 
00279 /*! \brief Set the column-to-column (x) resolution to expect for a received image.
00280     \param s The T.4 context.
00281     \param resolution The resolution, in pixels per metre. */
00282 void t4_rx_set_x_resolution(t4_state_t *s, int resolution);
00283 
00284 /*! \brief Set the sub-address of the fax, for inclusion in the file.
00285     \param s The T.4 context.
00286     \param sub_address The sub-address string. */
00287 void t4_rx_set_sub_address(t4_state_t *s, const char *sub_address);
00288 
00289 /*! \brief Set the identity of the remote machine, for inclusion in the file.
00290     \param s The T.4 context.
00291     \param ident The identity string. */
00292 void t4_rx_set_far_ident(t4_state_t *s, const char *ident);
00293 
00294 /*! \brief Set the vendor of the remote machine, for inclusion in the file.
00295     \param s The T.4 context.
00296     \param vendor The vendor string, or NULL. */
00297 void t4_rx_set_vendor(t4_state_t *s, const char *vendor);
00298 
00299 /*! \brief Set the model of the remote machine, for inclusion in the file.
00300     \param s The T.4 context.
00301     \param model The model string, or NULL. */
00302 void t4_rx_set_model(t4_state_t *s, const char *model);
00303 
00304 /*! \brief Allocate a T.4 receive handling context, and
00305            initialise it.
00306     \param s The T.4 context.
00307     \param file The name of the file to be sent.
00308     \return 0 for success, otherwise -1. */
00309 t4_state_t *t4_tx_create(const char *file, int start_page, int stop_page);
00310 
00311 /*! \brief Prepare for transmission of a document.
00312     \param s The T.4 context.
00313     \param file The name of the file to be sent.
00314     \param start_page The first page to send. -1 for no restriction.
00315     \param stop_page The last page to send. -1 for no restriction.
00316     \return The T.4 context, or NULL. */
00317 int t4_tx_init(t4_state_t *s, const char *file, int start_page, int stop_page);
00318 
00319 /*! \brief Prepare to send the next page of the current document.
00320     \param s The T.4 context.
00321     \return zero for success, -1 for failure. */
00322 int t4_tx_start_page(t4_state_t *s);
00323 
00324 /*! \brief Prepare the current page for a resend.
00325     \param s The T.4 context.
00326     \return zero for success, -1 for failure. */
00327 int t4_tx_restart_page(t4_state_t *s);
00328 
00329 /*! \brief Check for the existance of the next page. This information can
00330     be needed before it is determined that the current page is finished with.
00331     \param s The T.4 context.
00332     \return zero for next page found, -1 for failure. */
00333 int t4_tx_more_pages(t4_state_t *s);
00334 
00335 /*! \brief Complete the sending of a page.
00336     \param s The T.4 context.
00337     \return zero for success, -1 for failure. */
00338 int t4_tx_end_page(t4_state_t *s);
00339 
00340 /*! \brief Get the next bit of the current document page. The document will
00341            be padded for the current minimum scan line time. If the
00342            file does not contain an RTC (return to control) code at
00343            the end of the page, one will be added where appropriate.
00344     \param s The T.4 context.
00345     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00346             set (i.e. the returned value is 2 or 3). */
00347 int t4_tx_get_bit(t4_state_t *s);
00348 
00349 /*! \brief Get the next byte of the current document page. The document will
00350            be padded for the current minimum scan line time. If the
00351            file does not contain an RTC (return to control) code at
00352            the end of the page, one will be added where appropriate.
00353     \param s The T.4 context.
00354     \return The next byte. For the last byte of data, bit 8 is
00355             set. In this case, one or more bits of the byte may be padded with
00356             zeros, to complete the byte. */
00357 int t4_tx_get_byte(t4_state_t *s);
00358 
00359 /*! \brief Get the next chunk of the current document page. The document will
00360            be padded for the current minimum scan line time. If the
00361            file does not contain an RTC (return to control) code at
00362            the end of the page, one will be added where appropriate.
00363     \param s The T.4 context.
00364     \param buf The buffer into which the chunk is to written.
00365     \param max_len The maximum length of the chunk.
00366     \return The actual length of the chunk. If this is less than max_len it 
00367             indicates that the end of the document has been reached. */
00368 int t4_tx_get_chunk(t4_state_t *s, uint8_t buf[], int max_len);
00369 
00370 /*! \brief Return the next bit of the current document page, without actually
00371            moving forward in the buffer. The document will be padded for the
00372            current minimum scan line time. If the file does not contain an
00373            RTC (return to control) code at the end of the page, one will be
00374            added.
00375     \param s The T.4 context.
00376     \return The next bit (i.e. 0 or 1). For the last bit of data, bit 1 is
00377             set (i.e. the returned value is 2 or 3). */
00378 int t4_tx_check_bit(t4_state_t *s);
00379 
00380 /*! \brief End the transmission of a document. Tidy up, close the file and
00381            free the context. This should be used to end T.4 transmission
00382            started with t4_tx_create.
00383     \param s The T.4 context.
00384     \return 0 for success, otherwise -1. */
00385 int t4_tx_delete(t4_state_t *s);
00386 
00387 /*! \brief End the transmission of a document. Tidy up and close the file.
00388            This should be used to end T.4 transmission started with t4_tx_init.
00389     \param s The T.4 context.
00390     \return 0 for success, otherwise -1. */
00391 int t4_tx_end(t4_state_t *s);
00392 
00393 /*! \brief Set the encoding for the encoded data.
00394     \param s The T.4 context.
00395     \param encoding The encoding. */
00396 void t4_tx_set_tx_encoding(t4_state_t *s, int encoding);
00397 
00398 /*! \brief Set the minimum number of encoded bits per row. This allows the
00399            makes the encoding process to be set to comply with the minimum row
00400            time specified by a remote receiving machine.
00401     \param s The T.4 context.
00402     \param bits The minimum number of bits per row. */
00403 void t4_tx_set_min_row_bits(t4_state_t *s, int bits);
00404 
00405 /*! \brief Set the identity of the local machine, for inclusion in page headers.
00406     \param s The T.4 context.
00407     \param ident The identity string. */
00408 void t4_tx_set_local_ident(t4_state_t *s, const char *ident);
00409 
00410 /*! Set the info field, included in the header line included in each page of an encoded
00411     FAX. This is a string of up to 50 characters. Other information (date, local ident, etc.)
00412     are automatically included in the header. If the header info is set to NULL or a zero
00413     length string, no header lines will be added to the encoded FAX.
00414     \brief Set the header info.
00415     \param s The T.4 context.
00416     \param info A string, of up to 50 bytes, which will form the info field. */
00417 void t4_tx_set_header_info(t4_state_t *s, const char *info);
00418 
00419 /*! \brief Get the row-to-row (y) resolution of the current page.
00420     \param s The T.4 context.
00421     \return The resolution, in pixels per metre. */
00422 int t4_tx_get_y_resolution(t4_state_t *s);
00423 
00424 /*! \brief Get the column-to-column (x) resolution of the current page.
00425     \param s The T.4 context.
00426     \return The resolution, in pixels per metre. */
00427 int t4_tx_get_x_resolution(t4_state_t *s);
00428 
00429 /*! \brief Get the width of the current page, in pixel columns.
00430     \param s The T.4 context.
00431     \return The number of columns. */
00432 int t4_tx_get_image_width(t4_state_t *s);
00433 
00434 /*! Get the current image transfer statistics. 
00435     \brief Get the current transfer statistics.
00436     \param s The T.4 context.
00437     \param t A pointer to a statistics structure. */
00438 void t4_get_transfer_statistics(t4_state_t *s, t4_stats_t *t);
00439 
00440 /*! Get the short text name of an encoding format. 
00441     \brief Get the short text name of an encoding format.
00442     \param encoding The encoding type.
00443     \return A pointer to the string. */
00444 const char *t4_encoding_to_str(int encoding);
00445 
00446 #ifdef __cplusplus
00447 }
00448 #endif
00449 
00450 #endif
00451 /*- End of file ------------------------------------------------------------*/

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