libavfilter/formats.h

   1 /*
   2  * This file is part of Libav.
   3  *
   4  * Libav is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * Libav is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with Libav; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #ifndef AVFILTER_FORMATS_H
  20 #define AVFILTER_FORMATS_H
  21
  22 #include "avfilter.h"
  23
  24 /**
  25  * A list of supported formats for one end of a filter link. This is used
  26  * during the format negotiation process to try to pick the best format to
  27  * use to minimize the number of necessary conversions. Each filter gives a
  28  * list of the formats supported by each input and output pad. The list
  29  * given for each pad need not be distinct - they may be references to the
  30  * same list of formats, as is often the case when a filter supports multiple
  31  * formats, but will always output the same format as it is given in input.
  32  *
  33  * In this way, a list of possible input formats and a list of possible
  34  * output formats are associated with each link. When a set of formats is
  35  * negotiated over a link, the input and output lists are merged to form a
  36  * new list containing only the common elements of each list. In the case
  37  * that there were no common elements, a format conversion is necessary.
  38  * Otherwise, the lists are merged, and all other links which reference
  39  * either of the format lists involved in the merge are also affected.
  40  *
  41  * For example, consider the filter chain:
  42  * filter (a) --> (b) filter (b) --> (c) filter
  43  *
  44  * where the letters in parenthesis indicate a list of formats supported on
  45  * the input or output of the link. Suppose the lists are as follows:
  46  * (a) = {A, B}
  47  * (b) = {A, B, C}
  48  * (c) = {B, C}
  49  *
  50  * First, the first link's lists are merged, yielding:
  51  * filter (a) --> (a) filter (a) --> (c) filter
  52  *
  53  * Notice that format list (b) now refers to the same list as filter list (a).
  54  * Next, the lists for the second link are merged, yielding:
  55  * filter (a) --> (a) filter (a) --> (a) filter
  56  *
  57  * where (a) = {B}.
  58  *
  59  * Unfortunately, when the format lists at the two ends of a link are merged,
  60  * we must ensure that all links which reference either pre-merge format list
  61  * get updated as well. Therefore, we have the format list structure store a
  62  * pointer to each of the pointers to itself.
  63  */
  64 struct AVFilterFormats {
  65     unsigned format_count;      ///< number of formats
  66     int *formats;               ///< list of media formats
  67
  68     unsigned refcount;          ///< number of references to this list
  69     struct AVFilterFormats ***refs; ///< references to this list
  70 };
  71
  72 typedef struct AVFilterChannelLayouts {
  73     uint64_t *channel_layouts;  ///< list of channel layouts
  74     int    nb_channel_layouts;  ///< number of channel layouts
  75
  76     unsigned refcount;          ///< number of references to this list
  77     struct AVFilterChannelLayouts ***refs; ///< references to this list
  78 } AVFilterChannelLayouts;
  79
  80 /**
  81  * Return a channel layouts/samplerates list which contains the intersection of
  82  * the layouts/samplerates of a and b. Also, all the references of a, all the
  83  * references of b, and a and b themselves will be deallocated.
  84  *
  85  * If a and b do not share any common elements, neither is modified, and NULL
  86  * is returned.
  87  */
  88 AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
  89                                                  AVFilterChannelLayouts *b);
  90 AVFilterFormats *ff_merge_samplerates(AVFilterFormats *a,
  91                                       AVFilterFormats *b);
  92
  93 /**
  94  * Construct an empty AVFilterChannelLayouts/AVFilterFormats struct --
  95  * representing any channel layout/sample rate.
  96  */
  97 AVFilterChannelLayouts *ff_all_channel_layouts(void);
  98 AVFilterFormats *ff_all_samplerates(void);
  99
 100 /**
 101  * A helper for query_formats() which sets all links to the same list of channel
 102  * layouts/sample rates. If there are no links hooked to this filter, the list
 103  * is freed.
 104  */
 105 void ff_set_common_channel_layouts(AVFilterContext *ctx,
 106                                    AVFilterChannelLayouts *layouts);
 107 void ff_set_common_samplerates(AVFilterContext *ctx,
 108                                AVFilterFormats *samplerates);
 109
 110 /**
 111  * A helper for query_formats() which sets all links to the same list of
 112  * formats. If there are no links hooked to this filter, the list of formats is
 113  * freed.
 114  */
 115 void ff_set_common_formats(AVFilterContext *ctx, AVFilterFormats *formats);
 116
 117 int ff_add_channel_layout(AVFilterChannelLayouts **l, uint64_t channel_layout);
 118
 119 /**
 120  * Add *ref as a new reference to f.
 121  */
 122 void ff_channel_layouts_ref(AVFilterChannelLayouts *f,
 123                             AVFilterChannelLayouts **ref);
 124
 125 /**
 126  * Remove a reference to a channel layouts list.
 127  */
 128 void ff_channel_layouts_unref(AVFilterChannelLayouts **ref);
 129
 130 void ff_channel_layouts_changeref(AVFilterChannelLayouts **oldref,
 131                                   AVFilterChannelLayouts **newref);
 132
 133 int ff_default_query_formats(AVFilterContext *ctx);
 134
 135
 136 /**
 137  * Create a list of supported formats. This is intended for use in
 138  * AVFilter->query_formats().
 139  *
 140  * @param fmts list of media formats, terminated by -1
 141  * @return the format list, with no existing references
 142  */
 143 AVFilterFormats *ff_make_format_list(const int *fmts);
 144
 145 /**
 146  * Add fmt to the list of media formats contained in *avff.
 147  * If *avff is NULL the function allocates the filter formats struct
 148  * and puts its pointer in *avff.
 149  *
 150  * @return a non negative value in case of success, or a negative
 151  * value corresponding to an AVERROR code in case of error
 152  */
 153 int ff_add_format(AVFilterFormats **avff, int fmt);
 154
 155 /**
 156  * Return a list of all formats supported by Libav for the given media type.
 157  */
 158 AVFilterFormats *ff_all_formats(enum AVMediaType type);
 159
 160 /**
 161  * Construct a formats list containing all planar sample formats.
 162  */
 163 AVFilterFormats *ff_planar_sample_fmts(void);
 164
 165 /**
 166  * Return a format list which contains the intersection of the formats of
 167  * a and b. Also, all the references of a, all the references of b, and
 168  * a and b themselves will be deallocated.
 169  *
 170  * If a and b do not share any common formats, neither is modified, and NULL
 171  * is returned.
 172  */
 173 AVFilterFormats *ff_merge_formats(AVFilterFormats *a, AVFilterFormats *b);
 174
 175 /**
 176  * Add *ref as a new reference to formats.
 177  * That is the pointers will point like in the ascii art below:
 178  *   ________
 179  *  |formats |<--------.
 180  *  |  ____  |     ____|___________________
 181  *  | |refs| |    |  __|_
 182  *  | |* * | |    | |  | |  AVFilterLink
 183  *  | |* *--------->|*ref|
 184  *  | |____| |    | |____|
 185  *  |________|    |________________________
 186  */
 187 void ff_formats_ref(AVFilterFormats *formats, AVFilterFormats **ref);
 188
 189 /**
 190  * If *ref is non-NULL, remove *ref as a reference to the format list
 191  * it currently points to, deallocates that list if this was the last
 192  * reference, and sets *ref to NULL.
 193  *
 194  *         Before                                 After
 195  *   ________                               ________         NULL
 196  *  |formats |<--------.                   |formats |         ^
 197  *  |  ____  |     ____|________________   |  ____  |     ____|________________
 198  *  | |refs| |    |  __|_                  | |refs| |    |  __|_
 199  *  | |* * | |    | |  | |  AVFilterLink   | |* * | |    | |  | |  AVFilterLink
 200  *  | |* *--------->|*ref|                 | |*   | |    | |*ref|
 201  *  | |____| |    | |____|                 | |____| |    | |____|
 202  *  |________|    |_____________________   |________|    |_____________________
 203  */
 204 void ff_formats_unref(AVFilterFormats **ref);
 205
 206 /**
 207  *
 208  *         Before                                 After
 209  *   ________                         ________
 210  *  |formats |<---------.            |formats |<---------.
 211  *  |  ____  |       ___|___         |  ____  |       ___|___
 212  *  | |refs| |      |   |   |        | |refs| |      |   |   |   NULL
 213  *  | |* *--------->|*oldref|        | |* *--------->|*newref|     ^
 214  *  | |* * | |      |_______|        | |* * | |      |_______|  ___|___
 215  *  | |____| |                       | |____| |                |   |   |
 216  *  |________|                       |________|                |*oldref|
 217  *                                                             |_______|
 218  */
 219 void ff_formats_changeref(AVFilterFormats **oldref, AVFilterFormats **newref);
 220
 221 #endif /* AVFILTER_FORMATS_H */