lavc: Add coded bitstream read/write API

(cherry picked from commit 18f1706f331bf5dd565774eae680508c8d3a97ad)
(cherry picked from commit 44cde38c8acbef7d5250e6d1b52b1020871e093b)

1 files changed, 308 insertions, 0 deletions

diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
new file mode 100644
index 0000000000..2dc975ed79
--- /dev/null
+++ b/libavcodec/cbs.h
@@ -0,0 +1,308 @@
+/*
+ * 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_H
+#define AVCODEC_CBS_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "avcodec.h"
+
+
+/*
+ * This defines a framework for converting between a coded bitstream
+ * and structures defining all individual syntax elements found in
+ * such a stream.
+ *
+ * Conversion in both directions is possible.  Given a coded bitstream
+ * (any meaningful fragment), it can be parsed and decomposed into
+ * syntax elements stored in a set of codec-specific structures.
+ * Similarly, given a set of those same codec-specific structures the
+ * syntax elements can be serialised and combined to create a coded
+ * bitstream.
+ */
+
+struct CodedBitstreamType;
+
+/**
+ * The codec-specific type of a bitstream unit.
+ */
+typedef uint32_t CodedBitstreamUnitType;
+
+/**
+ * Coded bitstream unit structure.
+ *
+ * A bitstream unit the smallest element of a bitstream which
+ * is meaningful on its own.  For example, an H.264 NAL unit.
+ *
+ * See the codec-specific header for the meaning of this for any
+ * particular codec.
+ */
+typedef struct CodedBitstreamUnit {
+    /**
+     * Codec-specific type of this unit.
+     */
+    CodedBitstreamUnitType type;
+
+    /**
+     * Pointer to the directly-parsable bitstream form of this unit.
+     *
+     * May be NULL if the unit currently only exists in decomposed form.
+     */
+    uint8_t *data;
+    /**
+     * The number of bytes in the bitstream (including any padding bits
+     * in the final byte).
+     */
+    size_t   data_size;
+    /**
+     * The number of bits which should be ignored in the final byte.
+     *
+     * This supports non-byte-aligned bitstreams.
+     */
+    size_t   data_bit_padding;
+
+    /**
+     * Pointer to the decomposed form of this unit.
+     *
+     * The type of this structure depends on both the codec and the
+     * type of this unit.  May be NULL if the unit only exists in
+     * bitstream form.
+     */
+    void *content;
+    /**
+     * Whether the content was supplied externally.
+     *
+     * If so, it should not be freed when freeing the unit.
+     */
+    int   content_external;
+} CodedBitstreamUnit;
+
+/**
+ * Coded bitstream fragment structure, combining one or more units.
+ *
+ * This is any sequence of units.  It need not form some greater whole,
+ * though in many cases it will.  For example, an H.264 access unit,
+ * which is composed of a sequence of H.264 NAL units.
+ */
+typedef struct CodedBitstreamFragment {
+    /**
+     * Pointer to the bitstream form of this fragment.
+     *
+     * May be NULL if the fragment only exists as component units.
+     */
+    uint8_t *data;
+    /**
+     * The number of bytes in the bitstream.
+     *
+     * The number of bytes in the bitstream (including any padding bits
+     * in the final byte).
+     */
+    size_t   data_size;
+    /**
+     * The number of bits which should be ignored in the final byte.
+     */
+    size_t data_bit_padding;
+
+    /**
+     * Number of units in this fragment.
+     *
+     * This may be zero if the fragment only exists in bitstream form
+     * and has not been decomposed.
+     */
+    int              nb_units;
+    /**
+     * Pointer to an array of units of length nb_units.
+     *
+     * Must be NULL if nb_units is zero.
+     */
+    CodedBitstreamUnit *units;
+} CodedBitstreamFragment;
+
+/**
+ * Context structure for coded bitstream operations.
+ */
+typedef struct CodedBitstreamContext {
+    /**
+     * Logging context to be passed to all av_log() calls associated
+     * with this context.
+     */
+    void *log_ctx;
+
+    /**
+     * Internal codec-specific hooks.
+     */
+    const struct CodedBitstreamType *codec;
+
+    /**
+     * Internal codec-specific data.
+     *
+     * This contains any information needed when reading/writing
+     * bitsteams which will not necessarily be present in a fragment.
+     * For example, for H.264 it contains all currently visible
+     * parameter sets - they are required to determine the bitstream
+     * syntax but need not be present in every access unit.
+     */
+    void *priv_data;
+
+    /**
+     * Array of unit types which should be decomposed when reading.
+     *
+     * Types not in this list will be available in bitstream form only.
+     * If NULL, all supported types will be decomposed.
+     */
+    CodedBitstreamUnitType *decompose_unit_types;
+    /**
+     * Length of the decompose_unit_types array.
+     */
+    int nb_decompose_unit_types;
+
+    /**
+     * Enable trace output during read/write operations.
+     */
+    int trace_enable;
+    /**
+     * Log level to use for trace output.
+     *
+     * From AV_LOG_*; defaults to AV_LOG_TRACE.
+     */
+    int trace_level;
+} CodedBitstreamContext;
+
+
+/**
+ * Create and initialise a new context for the given codec.
+ */
+int ff_cbs_init(CodedBitstreamContext **ctx,
+                enum AVCodecID codec_id, void *log_ctx);
+
+/**
+ * Close a context and free all internal state.
+ */
+void ff_cbs_close(CodedBitstreamContext **ctx);
+
+
+/**
+ * Read the extradata bitstream found in codec parameters into a
+ * fragment, then split into units and decompose.
+ *
+ * This also updates the internal state, so will need to be called for
+ * codecs with extradata to read parameter sets necessary for further
+ * parsing even if the fragment itself is not desired.
+ */
+int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
+                          CodedBitstreamFragment *frag,
+                          const AVCodecParameters *par);
+
+/**
+ * Read the data bitstream from a packet into a fragment, then
+ * split into units and decompose.
+ *
+ * This also updates the internal state of the coded bitstream context
+ * with any persistent data from the fragment which may be required to
+ * read following fragments (e.g. parameter sets).
+ */
+int ff_cbs_read_packet(CodedBitstreamContext *ctx,
+                       CodedBitstreamFragment *frag,
+                       const AVPacket *pkt);
+
+/**
+ * Read a bitstream from a memory region into a fragment, then
+ * split into units and decompose.
+ *
+ * This also updates the internal state of the coded bitstream context
+ * with any persistent data from the fragment which may be required to
+ * read following fragments (e.g. parameter sets).
+ */
+int ff_cbs_read(CodedBitstreamContext *ctx,
+                CodedBitstreamFragment *frag,
+                const uint8_t *data, size_t size);
+
+
+/**
+ * Write the content of the fragment to its own internal buffer.
+ *
+ * Writes the content of all units and then assembles them into a new
+ * data buffer.  When modifying the content of decomposed units, this
+ * can be used to regenerate the bitstream form of units or the whole
+ * fragment so that it can be extracted for other use.
+ *
+ * This also updates the internal state of the coded bitstream context
+ * with any persistent data from the fragment which may be required to
+ * write following fragments (e.g. parameter sets).
+ */
+int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
+                               CodedBitstreamFragment *frag);
+
+/**
+ * Write the bitstream of a fragment to the extradata in codec parameters.
+ *
+ * This replaces any existing extradata in the structure.
+ */
+int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
+                           AVCodecParameters *par,
+                           CodedBitstreamFragment *frag);
+
+/**
+ * Write the bitstream of a fragment to a packet.
+ */
+int ff_cbs_write_packet(CodedBitstreamContext *ctx,
+                        AVPacket *pkt,
+                        CodedBitstreamFragment *frag);
+
+
+/**
+ * Free all allocated memory in a fragment.
+ */
+void ff_cbs_fragment_uninit(CodedBitstreamContext *ctx,
+                            CodedBitstreamFragment *frag);
+
+
+/**
+ * Insert a new unit into a fragment with the given content.
+ *
+ * The content structure continues to be owned by the caller, and
+ * will not be freed when the unit is.
+ */
+int ff_cbs_insert_unit_content(CodedBitstreamContext *ctx,
+                               CodedBitstreamFragment *frag,
+                               int position,
+                               CodedBitstreamUnitType type,
+                               void *content);
+
+/**
+ * Insert a new unit into a fragment with the given data bitstream.
+ *
+ * The data buffer will be owned by the unit after this operation.
+ */
+int ff_cbs_insert_unit_data(CodedBitstreamContext *ctx,
+                            CodedBitstreamFragment *frag,
+                            int position,
+                            CodedBitstreamUnitType type,
+                            uint8_t *data, size_t data_size);
+
+/**
+ * Delete a unit from a fragment and free all memory it uses.
+ */
+int ff_cbs_delete_unit(CodedBitstreamContext *ctx,
+                       CodedBitstreamFragment *frag,
+                       int position);
+
+
+#endif /* AVCODEC_CBS_H */