lavfi: make formats API private on next bump.

It is only useful inside filters and we don't allow user filters for
now.

1 files changed, 138 insertions, 0 deletions

diff --git a/libavfilter/formats.h b/libavfilter/formats.h
index 9acd31f38a..8961cb1a65 100644
--- a/libavfilter/formats.h
+++ b/libavfilter/formats.h
@@ -21,6 +21,56 @@
 
 #include "avfilter.h"
 
+/**
+ * A list of supported formats for one end of a filter link. This is used
+ * during the format negotiation process to try to pick the best format to
+ * use to minimize the number of necessary conversions. Each filter gives a
+ * list of the formats supported by each input and output pad. The list
+ * given for each pad need not be distinct - they may be references to the
+ * same list of formats, as is often the case when a filter supports multiple
+ * formats, but will always output the same format as it is given in input.
+ *
+ * In this way, a list of possible input formats and a list of possible
+ * output formats are associated with each link. When a set of formats is
+ * negotiated over a link, the input and output lists are merged to form a
+ * new list containing only the common elements of each list. In the case
+ * that there were no common elements, a format conversion is necessary.
+ * Otherwise, the lists are merged, and all other links which reference
+ * either of the format lists involved in the merge are also affected.
+ *
+ * For example, consider the filter chain:
+ * filter (a) --> (b) filter (b) --> (c) filter
+ *
+ * where the letters in parenthesis indicate a list of formats supported on
+ * the input or output of the link. Suppose the lists are as follows:
+ * (a) = {A, B}
+ * (b) = {A, B, C}
+ * (c) = {B, C}
+ *
+ * First, the first link's lists are merged, yielding:
+ * filter (a) --> (a) filter (a) --> (c) filter
+ *
+ * Notice that format list (b) now refers to the same list as filter list (a).
+ * Next, the lists for the second link are merged, yielding:
+ * filter (a) --> (a) filter (a) --> (a) filter
+ *
+ * where (a) = {B}.
+ *
+ * Unfortunately, when the format lists at the two ends of a link are merged,
+ * we must ensure that all links which reference either pre-merge format list
+ * get updated as well. Therefore, we have the format list structure store a
+ * pointer to each of the pointers to itself.
+ */
+#if !FF_API_FILTERS_PUBLIC
+struct AVFilterFormats {
+    unsigned format_count;      ///< number of formats
+    int *formats;               ///< list of media formats
+
+    unsigned refcount;          ///< number of references to this list
+    struct AVFilterFormats ***refs; ///< references to this list
+};
+#endif
+
 typedef struct AVFilterChannelLayouts {
     uint64_t *channel_layouts;  ///< list of channel layouts
     int    nb_channel_layouts;  ///< number of channel layouts
@@ -59,6 +109,13 @@ void ff_set_common_channel_layouts(AVFilterContext *ctx,
 void ff_set_common_samplerates(AVFilterContext *ctx,
                                AVFilterFormats *samplerates);
 
+/**
+ * A helper for query_formats() which sets all links to the same list of
+ * formats. If there are no links hooked to this filter, the list of formats is
+ * freed.
+ */
+void ff_set_common_formats(AVFilterContext *ctx, AVFilterFormats *formats);
+
 int ff_add_channel_layout(AVFilterChannelLayouts **l, uint64_t channel_layout);
 
 /**
@@ -77,4 +134,85 @@ void ff_channel_layouts_changeref(AVFilterChannelLayouts **oldref,
 
 int ff_default_query_formats(AVFilterContext *ctx);
 
+
+/**
+ * Create a list of supported formats. This is intended for use in
+ * AVFilter->query_formats().
+ *
+ * @param fmts list of media formats, terminated by -1
+ * @return the format list, with no existing references
+ */
+AVFilterFormats *ff_make_format_list(const int *fmts);
+
+/**
+ * Add fmt to the list of media formats contained in *avff.
+ * If *avff is NULL the function allocates the filter formats struct
+ * and puts its pointer in *avff.
+ *
+ * @return a non negative value in case of success, or a negative
+ * value corresponding to an AVERROR code in case of error
+ */
+int ff_add_format(AVFilterFormats **avff, int fmt);
+
+/**
+ * Return a list of all formats supported by Libav for the given media type.
+ */
+AVFilterFormats *ff_all_formats(enum AVMediaType type);
+
+/**
+ * Return a format list which contains the intersection of the formats of
+ * a and b. Also, all the references of a, all the references of b, and
+ * a and b themselves will be deallocated.
+ *
+ * If a and b do not share any common formats, neither is modified, and NULL
+ * is returned.
+ */
+AVFilterFormats *ff_merge_formats(AVFilterFormats *a, AVFilterFormats *b);
+
+/**
+ * Add *ref as a new reference to formats.
+ * That is the pointers will point like in the ascii art below:
+ *   ________
+ *  |formats |<--------.
+ *  |  ____  |     ____|___________________
+ *  | |refs| |    |  __|_
+ *  | |* * | |    | |  | |  AVFilterLink
+ *  | |* *--------->|*ref|
+ *  | |____| |    | |____|
+ *  |________|    |________________________
+ */
+void ff_formats_ref(AVFilterFormats *formats, AVFilterFormats **ref);
+
+/**
+ * If *ref is non-NULL, remove *ref as a reference to the format list
+ * it currently points to, deallocates that list if this was the last
+ * reference, and sets *ref to NULL.
+ *
+ *         Before                                 After
+ *   ________                               ________         NULL
+ *  |formats |<--------.                   |formats |         ^
+ *  |  ____  |     ____|________________   |  ____  |     ____|________________
+ *  | |refs| |    |  __|_                  | |refs| |    |  __|_
+ *  | |* * | |    | |  | |  AVFilterLink   | |* * | |    | |  | |  AVFilterLink
+ *  | |* *--------->|*ref|                 | |*   | |    | |*ref|
+ *  | |____| |    | |____|                 | |____| |    | |____|
+ *  |________|    |_____________________   |________|    |_____________________
+ */
+void ff_formats_unref(AVFilterFormats **ref);
+
+/**
+ *
+ *         Before                                 After
+ *   ________                         ________
+ *  |formats |<---------.            |formats |<---------.
+ *  |  ____  |       ___|___         |  ____  |       ___|___
+ *  | |refs| |      |   |   |        | |refs| |      |   |   |   NULL
+ *  | |* *--------->|*oldref|        | |* *--------->|*newref|     ^
+ *  | |* * | |      |_______|        | |* * | |      |_______|  ___|___
+ *  | |____| |                       | |____| |                |   |   |
+ *  |________|                       |________|                |*oldref|
+ *                                                             |_______|
+ */
+void ff_formats_changeref(AVFilterFormats **oldref, AVFilterFormats **newref);
+
 #endif // AVFILTER_FORMATS_H