---
libavcodec/cbs.h | 35 +++
libavcodec/cbs_internal.h | 3 +++
2 files changed, 34 insertions(+), 4 deletions(-)
diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
index 85c7b5557..ffeca057a 100644
--- a/libavcodec/cbs.h
+++ b/libavcodec/cbs.h
@@ -25,6 +25,19 @@
#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;
/**
@@ -39,7 +52,7 @@ typedef uint32_t CodedBitstreamUnitType;
/**
* Coded bitstream unit structure.
*
- * A bitstream unit the the smallest element of a bitstream which
+ * 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
@@ -52,7 +65,7 @@ typedef struct CodedBitstreamUnit {
CodedBitstreamUnitType type;
/**
- * Pointer to the bitstream form of this unit.
+ * Pointer to the directly-parsable bitstream form of this unit.
*
* May be NULL if the unit currently only exists in decomposed form.
*/
@@ -114,7 +127,7 @@ typedef struct CodedBitstreamFragment {
/**
* Number of units in this fragment.
*
- * This may be zero if the fragment only exists in bistream form
+ * This may be zero if the fragment only exists in bitstream form
* and has not been decomposed.
*/
int nb_units;
@@ -162,7 +175,7 @@ typedef struct CodedBitstreamContext {
/**
* Length of the decompose_unit_types array.
*/
-intnb_decompose_unit_types;
+int nb_decompose_unit_types;
/**
* Enable trace output during read/write operations.
@@ -204,6 +217,10 @@ int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
/**
* 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,
@@ -212,6 +229,10 @@ int ff_cbs_read_packet(CodedBitstreamContext *ctx,
/**
* 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,
@@ -225,12 +246,18 @@ int ff_cbs_read(CodedBitstreamContext *ctx,
* 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,
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index dddeae9d5..1a1c22f06 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -32,6 +32,9 @@ typedef struct CodedBitstreamType {
// Split frag->data into coded bitstream units, creating the
// frag->units array. Fill data but not content on each unit.
+// The header argument should be set if the fragment came from
+// a header block, which may require different parsing for some
+// codecs (e.g. the AVCC header in H.264).
int (*split_fragment)(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int header);
--
2.15.1
___
libav-devel mailing list
libav-devel@libav.org
https://lists.libav.org/mailman/listinfo/libav-devel
