2 * SpanDSP - a series of DSP components for telephony
4 * private/t4_t6_decode.h - definitions for T.4/T.6 fax decoding
6 * Written by Steve Underwood <steveu@coppice.org>
8 * Copyright (C) 2003, 2009 Steve Underwood
10 * All rights reserved.
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Lesser General Public License version 2.1,
14 * as published by the Free Software Foundation.
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 Lesser General Public License for more details.
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
26 #if !defined(_SPANDSP_PRIVATE_T4_T6_DECODE_H_)
27 #define _SPANDSP_PRIVATE_T4_T6_DECODE_H_
30 T.4 1D, T4 2D and T6 decompressor state.
32 struct t4_t6_decode_state_s
34 /*! \brief The type of compression used between the FAX machines. */
36 /*! \brief Width of the current page, in pixels. */
39 /*! \brief Callback function to write a row of pixels to the image destination. */
40 t4_row_write_handler_t row_write_handler;
41 /*! \brief Opaque pointer passed to row_write_handler. */
42 void *row_write_user_data;
44 /*! \brief A pointer into the image buffer indicating where the last row begins */
45 int last_row_starts_at;
47 /*! \brief This variable is used to count the consecutive EOLS we have seen. If it
48 reaches six, this is the end of the image. It is initially set to -1 for
49 1D and 2D decoding, as an indicator that we must wait for the first EOL,
50 before decoding any image data. */
53 /*! \brief The reference or starting changing element on the coding line. At the
54 start of the coding line, a0 is set on an imaginary white changing element
55 situated just before the first element on the line. During the coding of
56 the coding line, the position of a0 is defined by the previous coding mode.
57 (See T.4/4.2.1.3.2.). */
59 /*! \brief The first changing element on the reference line to the right of a0 and of
60 opposite colour to a0. */
62 /*! \brief The length of the in-progress run of black or white. */
64 /*! \brief 2D horizontal mode control. */
66 /*! \brief TRUE if the current run is black */
69 /*! \brief The current step into the current row run-lengths buffer. */
71 /*! \brief The current step into the reference row run-lengths buffer. */
74 /*! \brief Incoming bit buffer for decompression. */
75 uint32_t rx_bitstream;
76 /*! \brief The number of bits currently in rx_bitstream. */
78 /*! \brief The number of bits to be skipped before trying to match the next code word. */
81 /*! \brief Decoded pixel buffer. */
82 //uint32_t pixel_stream;
83 /*! \brief The number of bits currently in pixel_stream. */
86 /*! \brief Current pixel row number. */
89 /*! \brief The current number of consecutive bad rows. */
91 /*! \brief The longest run of consecutive bad rows seen in the current page. */
92 int longest_bad_row_run;
93 /*! \brief The total number of bad rows in the current page. */
96 /*! \brief Error and flow logging control */
97 //logging_state_t logging;
101 /*- End of file ------------------------------------------------------------*/