cbs: Implement common parts of cbs-based bitstream filters separately

This allows removal of a lot of duplicated code between BSFs.

1 files changed, 131 insertions, 0 deletions

diff --git a/libavcodec/cbs_bsf.h b/libavcodec/cbs_bsf.h
new file mode 100644
index 0000000000..6be95abc3f
--- /dev/null
+++ b/libavcodec/cbs_bsf.h
@@ -0,0 +1,131 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_CBS_BSF_H
+#define AVCODEC_CBS_BSF_H
+
+#include "cbs.h"
+
+
+typedef struct CBSBSFType {
+    enum AVCodecID codec_id;
+
+    // Name of a frame fragment in this codec (e.g. "access unit",
+    // "temporal unit").
+    const char *fragment_name;
+
+    // Name of a unit for this BSF, for use in error messages (e.g.
+    // "NAL unit", "OBU").
+    const char *unit_name;
+
+    // Update the content of a fragment with whatever metadata changes
+    // are desired.  The associated AVPacket is provided so that any side
+    // data associated with the fragment can be inspected or edited.  If
+    // pkt is NULL, then an extradata header fragment is being updated.
+    int (*update_fragment)(AVBSFContext *bsf, AVPacket *pkt,
+                           CodedBitstreamFragment *frag);
+} CBSBSFType;
+
+// Common structure for all generic CBS BSF users.  An instance of this
+// structure must be the first member of the BSF private context (to be
+// pointed to by AVBSFContext.priv_data).
+typedef struct CBSBSFContext {
+    const AVClass         *class;
+    const CBSBSFType      *type;
+
+    CodedBitstreamContext *input;
+    CodedBitstreamContext *output;
+    CodedBitstreamFragment fragment;
+} CBSBSFContext;
+
+/**
+ * Initialise generic CBS BSF setup.
+ *
+ * Creates the input and output CBS instances, and applies the filter to
+ * the extradata on the input codecpar if any is present.
+ *
+ * Since it calls the update_fragment() function immediately to deal with
+ * extradata, this should be called after any codec-specific setup is done
+ * (probably at the end of the AVBitStreamFilter.init function).
+ */
+int ff_cbs_bsf_generic_init(AVBSFContext *bsf, const CBSBSFType *type);
+
+/**
+ * Close a generic CBS BSF instance.
+ *
+ * If no other deinitialisation is required then this function can be used
+ * directly as AVBitStreamFilter.close.
+ */
+void ff_cbs_bsf_generic_close(AVBSFContext *bsf);
+
+/**
+ * Filter operation for CBS BSF.
+ *
+ * Reads the input packet into a CBS fragment, calls update_fragment() on
+ * it, then writes the result to an output packet.  If the input packet
+ * has AV_PKT_DATA_NEW_EXTRADATA side-data associated with it then it does
+ * the same thing to that new extradata to form the output side-data first.
+ *
+ * If the BSF does not do anything else then this function can be used
+ * directly as AVBitStreamFilter.filter.
+ */
+int ff_cbs_bsf_generic_filter(AVBSFContext *bsf, AVPacket *pkt);
+
+
+// Options for element manipulation.
+enum {
+    // Pass this element through unchanged.
+    BSF_ELEMENT_PASS,
+    // Insert this element, replacing any existing instances of it.
+    // Associated values may be provided explicitly (as addtional options)
+    // or implicitly (either as side data or deduced from other parts of
+    // the stream).
+    BSF_ELEMENT_INSERT,
+    // Remove this element if it appears in the stream.
+    BSF_ELEMENT_REMOVE,
+    // Extract this element to side data, so that further manipulation
+    // can happen elsewhere.
+    BSF_ELEMENT_EXTRACT,
+};
+
+#define BSF_ELEMENT_OPTIONS_PIR(name, help, field, opt_flags) \
+    { name, help, OFFSET(field), AV_OPT_TYPE_INT, \
+        { .i64 = BSF_ELEMENT_PASS }, \
+        BSF_ELEMENT_PASS, BSF_ELEMENT_REMOVE, opt_flags, name }, \
+    { "pass",   NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_PASS   }, .flags = opt_flags, .unit = name }, \
+    { "insert", NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_INSERT }, .flags = opt_flags, .unit = name }, \
+    { "remove", NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_REMOVE }, .flags = opt_flags, .unit = name }
+
+#define BSF_ELEMENT_OPTIONS_PIRE(name, help, field, opt_flags) \
+    { name, help, OFFSET(field), AV_OPT_TYPE_INT, \
+        { .i64 = BSF_ELEMENT_PASS }, \
+        BSF_ELEMENT_PASS, BSF_ELEMENT_EXTRACT, opt_flags, name }, \
+    { "pass",   NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_PASS    }, .flags = opt_flags, .unit = name }, \
+    { "insert", NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_INSERT  }, .flags = opt_flags, .unit = name }, \
+    { "remove", NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_REMOVE  }, .flags = opt_flags, .unit = name }, \
+    { "extract", NULL, 0, AV_OPT_TYPE_CONST, \
+        { .i64 = BSF_ELEMENT_EXTRACT }, .flags = opt_flags, .unit = name } \
+
+
+#endif /* AVCODEC_CBS_BSF_H */