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formats.h
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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  */
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
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  */
92 
93 /**
94  * Construct an empty AVFilterChannelLayouts/AVFilterFormats struct --
95  * representing any channel layout/sample rate.
96  */
99 
101 
102 
103 /**
104  * A helper for query_formats() which sets all links to the same list of channel
105  * layouts/sample rates. If there are no links hooked to this filter, the list
106  * is freed.
107  */
111  AVFilterFormats *samplerates);
112 
113 /**
114  * A helper for query_formats() which sets all links to the same list of
115  * formats. If there are no links hooked to this filter, the list of formats is
116  * freed.
117  */
119 
120 int ff_add_channel_layout(AVFilterChannelLayouts **l, uint64_t channel_layout);
121 
122 /**
123  * Add *ref as a new reference to f.
124  */
126  AVFilterChannelLayouts **ref);
127 
128 /**
129  * Remove a reference to a channel layouts list.
130  */
132 
134  AVFilterChannelLayouts **newref);
135 
137 
138 
139 /**
140  * Create a list of supported formats. This is intended for use in
141  * AVFilter->query_formats().
142  *
143  * @param fmts list of media formats, terminated by -1
144  * @return the format list, with no existing references
145  */
146 AVFilterFormats *ff_make_format_list(const int *fmts);
147 
148 /**
149  * Add fmt to the list of media formats contained in *avff.
150  * If *avff is NULL the function allocates the filter formats struct
151  * and puts its pointer in *avff.
152  *
153  * @return a non negative value in case of success, or a negative
154  * value corresponding to an AVERROR code in case of error
155  */
156 int ff_add_format(AVFilterFormats **avff, int64_t fmt);
157 
158 /**
159  * Return a list of all formats supported by FFmpeg for the given media type.
160  */
162 
163 /**
164  * Construct a formats list containing all planar sample formats.
165  */
167 
168 /**
169  * Return a format list which contains the intersection of the formats of
170  * a and b. Also, all the references of a, all the references of b, and
171  * a and b themselves will be deallocated.
172  *
173  * If a and b do not share any common formats, neither is modified, and NULL
174  * is returned.
175  */
177 
178 /**
179  * Add *ref as a new reference to formats.
180  * That is the pointers will point like in the ascii art below:
181  * ________
182  * |formats |<--------.
183  * | ____ | ____|___________________
184  * | |refs| | | __|_
185  * | |* * | | | | | | AVFilterLink
186  * | |* *--------->|*ref|
187  * | |____| | | |____|
188  * |________| |________________________
189  */
191 
192 /**
193  * If *ref is non-NULL, remove *ref as a reference to the format list
194  * it currently points to, deallocates that list if this was the last
195  * reference, and sets *ref to NULL.
196  *
197  * Before After
198  * ________ ________ NULL
199  * |formats |<--------. |formats | ^
200  * | ____ | ____|________________ | ____ | ____|________________
201  * | |refs| | | __|_ | |refs| | | __|_
202  * | |* * | | | | | | AVFilterLink | |* * | | | | | | AVFilterLink
203  * | |* *--------->|*ref| | |* | | | |*ref|
204  * | |____| | | |____| | |____| | | |____|
205  * |________| |_____________________ |________| |_____________________
206  */
208 
209 /**
210  *
211  * Before After
212  * ________ ________
213  * |formats |<---------. |formats |<---------.
214  * | ____ | ___|___ | ____ | ___|___
215  * | |refs| | | | | | |refs| | | | | NULL
216  * | |* *--------->|*oldref| | |* *--------->|*newref| ^
217  * | |* * | | |_______| | |* * | | |_______| ___|___
218  * | |____| | | |____| | | | |
219  * |________| |________| |*oldref|
220  * |_______|
221  */
222 void ff_formats_changeref(AVFilterFormats **oldref, AVFilterFormats **newref);
223 
224 #endif /* AVFILTER_FORMATS_H */