avutil/channel_layout: Add a new channel layout API

The new API is more extensible and allows for custom layouts.
More accurate information is exported, eg for decoders that do not
set a channel layout, lavc will not make one up for them.

Deprecate the old API working with just uint64_t bitmasks.

Expanded and completed by Vittorio Giovara <vittorio.giovara@gmail.com>
and James Almer <jamrial@gmail.com>.
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 493 insertions, 32 deletions

diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h
index d39ae1177a..b1456c245e 100644
--- a/libavutil/channel_layout.h
+++ b/libavutil/channel_layout.h
@@ -23,6 +23,10 @@
 #define AVUTIL_CHANNEL_LAYOUT_H
 
 #include <stdint.h>
+#include <stdlib.h>
+
+#include "version.h"
+#include "attributes.h"
 
 /**
  * @file
@@ -34,6 +38,71 @@
  * @{
  */
 
+enum AVChannel {
+    ///< Invalid channel index
+    AV_CHAN_NONE = -1,
+    AV_CHAN_FRONT_LEFT,
+    AV_CHAN_FRONT_RIGHT,
+    AV_CHAN_FRONT_CENTER,
+    AV_CHAN_LOW_FREQUENCY,
+    AV_CHAN_BACK_LEFT,
+    AV_CHAN_BACK_RIGHT,
+    AV_CHAN_FRONT_LEFT_OF_CENTER,
+    AV_CHAN_FRONT_RIGHT_OF_CENTER,
+    AV_CHAN_BACK_CENTER,
+    AV_CHAN_SIDE_LEFT,
+    AV_CHAN_SIDE_RIGHT,
+    AV_CHAN_TOP_CENTER,
+    AV_CHAN_TOP_FRONT_LEFT,
+    AV_CHAN_TOP_FRONT_CENTER,
+    AV_CHAN_TOP_FRONT_RIGHT,
+    AV_CHAN_TOP_BACK_LEFT,
+    AV_CHAN_TOP_BACK_CENTER,
+    AV_CHAN_TOP_BACK_RIGHT,
+    /** Stereo downmix. */
+    AV_CHAN_STEREO_LEFT = 29,
+    /** See above. */
+    AV_CHAN_STEREO_RIGHT,
+    AV_CHAN_WIDE_LEFT,
+    AV_CHAN_WIDE_RIGHT,
+    AV_CHAN_SURROUND_DIRECT_LEFT,
+    AV_CHAN_SURROUND_DIRECT_RIGHT,
+    AV_CHAN_LOW_FREQUENCY_2,
+    AV_CHAN_TOP_SIDE_LEFT,
+    AV_CHAN_TOP_SIDE_RIGHT,
+    AV_CHAN_BOTTOM_FRONT_CENTER,
+    AV_CHAN_BOTTOM_FRONT_LEFT,
+    AV_CHAN_BOTTOM_FRONT_RIGHT,
+
+    /** Channel is empty can be safely skipped. */
+    AV_CHAN_UNUSED = 0x200,
+
+    /** Channel contains data, but its position is unknown. */
+    AV_CHAN_UNKNOWN = 0x300,
+};
+
+enum AVChannelOrder {
+    /**
+     * Only the channel count is specified, without any further information
+     * about the channel order.
+     */
+    AV_CHANNEL_ORDER_UNSPEC,
+    /**
+     * The native channel order, i.e. the channels are in the same order in
+     * which they are defined in the AVChannel enum. This supports up to 63
+     * different channels.
+     */
+    AV_CHANNEL_ORDER_NATIVE,
+    /**
+     * The channel order does not correspond to any other predefined order and
+     * is stored as an explicit map. For example, this could be used to support
+     * layouts with 64 or more channels, or with empty/skipped (AV_CHAN_SILENCE)
+     * channels at arbitrary positions.
+     */
+    AV_CHANNEL_ORDER_CUSTOM,
+};
+
+
 /**
  * @defgroup channel_masks Audio channel masks
  *
@@ -46,41 +115,46 @@
  *
  * @{
  */
-#define AV_CH_FRONT_LEFT             0x00000001
-#define AV_CH_FRONT_RIGHT            0x00000002
-#define AV_CH_FRONT_CENTER           0x00000004
-#define AV_CH_LOW_FREQUENCY          0x00000008
-#define AV_CH_BACK_LEFT              0x00000010
-#define AV_CH_BACK_RIGHT             0x00000020
-#define AV_CH_FRONT_LEFT_OF_CENTER   0x00000040
-#define AV_CH_FRONT_RIGHT_OF_CENTER  0x00000080
-#define AV_CH_BACK_CENTER            0x00000100
-#define AV_CH_SIDE_LEFT              0x00000200
-#define AV_CH_SIDE_RIGHT             0x00000400
-#define AV_CH_TOP_CENTER             0x00000800
-#define AV_CH_TOP_FRONT_LEFT         0x00001000
-#define AV_CH_TOP_FRONT_CENTER       0x00002000
-#define AV_CH_TOP_FRONT_RIGHT        0x00004000
-#define AV_CH_TOP_BACK_LEFT          0x00008000
-#define AV_CH_TOP_BACK_CENTER        0x00010000
-#define AV_CH_TOP_BACK_RIGHT         0x00020000
-#define AV_CH_STEREO_LEFT            0x20000000  ///< Stereo downmix.
-#define AV_CH_STEREO_RIGHT           0x40000000  ///< See AV_CH_STEREO_LEFT.
-#define AV_CH_WIDE_LEFT              0x0000000080000000ULL
-#define AV_CH_WIDE_RIGHT             0x0000000100000000ULL
-#define AV_CH_SURROUND_DIRECT_LEFT   0x0000000200000000ULL
-#define AV_CH_SURROUND_DIRECT_RIGHT  0x0000000400000000ULL
-#define AV_CH_LOW_FREQUENCY_2        0x0000000800000000ULL
-#define AV_CH_TOP_SIDE_LEFT          0x0000001000000000ULL
-#define AV_CH_TOP_SIDE_RIGHT         0x0000002000000000ULL
-#define AV_CH_BOTTOM_FRONT_CENTER    0x0000004000000000ULL
-#define AV_CH_BOTTOM_FRONT_LEFT      0x0000008000000000ULL
-#define AV_CH_BOTTOM_FRONT_RIGHT     0x0000010000000000ULL
+#define AV_CH_FRONT_LEFT             (1ULL << AV_CHAN_FRONT_LEFT           )
+#define AV_CH_FRONT_RIGHT            (1ULL << AV_CHAN_FRONT_RIGHT          )
+#define AV_CH_FRONT_CENTER           (1ULL << AV_CHAN_FRONT_CENTER         )
+#define AV_CH_LOW_FREQUENCY          (1ULL << AV_CHAN_LOW_FREQUENCY        )
+#define AV_CH_BACK_LEFT              (1ULL << AV_CHAN_BACK_LEFT            )
+#define AV_CH_BACK_RIGHT             (1ULL << AV_CHAN_BACK_RIGHT           )
+#define AV_CH_FRONT_LEFT_OF_CENTER   (1ULL << AV_CHAN_FRONT_LEFT_OF_CENTER )
+#define AV_CH_FRONT_RIGHT_OF_CENTER  (1ULL << AV_CHAN_FRONT_RIGHT_OF_CENTER)
+#define AV_CH_BACK_CENTER            (1ULL << AV_CHAN_BACK_CENTER          )
+#define AV_CH_SIDE_LEFT              (1ULL << AV_CHAN_SIDE_LEFT            )
+#define AV_CH_SIDE_RIGHT             (1ULL << AV_CHAN_SIDE_RIGHT           )
+#define AV_CH_TOP_CENTER             (1ULL << AV_CHAN_TOP_CENTER           )
+#define AV_CH_TOP_FRONT_LEFT         (1ULL << AV_CHAN_TOP_FRONT_LEFT       )
+#define AV_CH_TOP_FRONT_CENTER       (1ULL << AV_CHAN_TOP_FRONT_CENTER     )
+#define AV_CH_TOP_FRONT_RIGHT        (1ULL << AV_CHAN_TOP_FRONT_RIGHT      )
+#define AV_CH_TOP_BACK_LEFT          (1ULL << AV_CHAN_TOP_BACK_LEFT        )
+#define AV_CH_TOP_BACK_CENTER        (1ULL << AV_CHAN_TOP_BACK_CENTER      )
+#define AV_CH_TOP_BACK_RIGHT         (1ULL << AV_CHAN_TOP_BACK_RIGHT       )
+#define AV_CH_STEREO_LEFT            (1ULL << AV_CHAN_STEREO_LEFT          )
+#define AV_CH_STEREO_RIGHT           (1ULL << AV_CHAN_STEREO_RIGHT         )
+#define AV_CH_WIDE_LEFT              (1ULL << AV_CHAN_WIDE_LEFT            )
+#define AV_CH_WIDE_RIGHT             (1ULL << AV_CHAN_WIDE_RIGHT           )
+#define AV_CH_SURROUND_DIRECT_LEFT   (1ULL << AV_CHAN_SURROUND_DIRECT_LEFT )
+#define AV_CH_SURROUND_DIRECT_RIGHT  (1ULL << AV_CHAN_SURROUND_DIRECT_RIGHT)
+#define AV_CH_LOW_FREQUENCY_2        (1ULL << AV_CHAN_LOW_FREQUENCY_2      )
+#define AV_CH_TOP_SIDE_LEFT          (1ULL << AV_CHAN_TOP_SIDE_LEFT        )
+#define AV_CH_TOP_SIDE_RIGHT         (1ULL << AV_CHAN_TOP_SIDE_RIGHT       )
+#define AV_CH_BOTTOM_FRONT_CENTER    (1ULL << AV_CHAN_BOTTOM_FRONT_CENTER  )
+#define AV_CH_BOTTOM_FRONT_LEFT      (1ULL << AV_CHAN_BOTTOM_FRONT_LEFT    )
+#define AV_CH_BOTTOM_FRONT_RIGHT     (1ULL << AV_CHAN_BOTTOM_FRONT_RIGHT   )
 
+#if FF_API_OLD_CHANNEL_LAYOUT
 /** Channel mask value used for AVCodecContext.request_channel_layout
     to indicate that the user requests the channel order of the decoder output
-    to be the native codec channel order. */
+    to be the native codec channel order.
+    @deprecated channel order is now indicated in a special field in
+                AVChannelLayout
+    */
 #define AV_CH_LAYOUT_NATIVE          0x8000000000000000ULL
+#endif
 
 /**
  * @}
@@ -129,6 +203,141 @@ enum AVMatrixEncoding {
 };
 
 /**
+ * @}
+ */
+
+/**
+ * An AVChannelCustom defines a single channel within a custom order layout
+ *
+ * Unlike most structures in FFmpeg, sizeof(AVChannelCustom) is a part of the
+ * public ABI.
+ *
+ * No new fields may be added to it without a major version bump.
+ */
+typedef struct AVChannelCustom {
+    enum AVChannel id;
+    char name[16];
+    void *opaque;
+} AVChannelCustom;
+
+/**
+ * An AVChannelLayout holds information about the channel layout of audio data.
+ *
+ * A channel layout here is defined as a set of channels ordered in a specific
+ * way (unless the channel order is AV_CHANNEL_ORDER_UNSPEC, in which case an
+ * AVChannelLayout carries only the channel count).
+ *
+ * Unlike most structures in Libav, sizeof(AVChannelLayout) is a part of the
+ * public ABI and may be used by the caller. E.g. it may be allocated on stack
+ * or embedded in caller-defined structs.
+ *
+ * AVChannelLayout can be initialized as follows:
+ * - default initialization with {0}, followed by setting all used fields
+ *   correctly;
+ * - by assigning one of the predefined AV_CHANNEL_LAYOUT_* initializers;
+ * - with a constructor function, such as av_channel_layout_default(),
+ *   av_channel_layout_from_mask() or av_channel_layout_from_string().
+ *
+ * The channel layout must be unitialized with av_channel_layout_uninit()
+ *
+ * Copying an AVChannelLayout via assigning is forbidden,
+ * av_channel_layout_copy() must be used instead (and its return value should
+ * be checked)
+ *
+ * No new fields may be added to it without a major version bump, except for
+ * new elements of the union fitting in sizeof(uint64_t).
+ */
+typedef struct AVChannelLayout {
+    /**
+     * Channel order used in this layout.
+     * This is a mandatory field.
+     */
+    enum AVChannelOrder order;
+
+    /**
+     * Number of channels in this layout. Mandatory field.
+     */
+    int nb_channels;
+
+    /**
+     * Details about which channels are present in this layout.
+     * For AV_CHANNEL_ORDER_UNSPEC, this field is undefined and must not be
+     * used.
+     */
+    union {
+        /**
+         * This member must be used for AV_CHANNEL_ORDER_NATIVE.
+         * It is a bitmask, where the position of each set bit means that the
+         * AVChannel with the corresponding value is present.
+         *
+         * I.e. when (mask & (1 << AV_CHAN_FOO)) is non-zero, then AV_CHAN_FOO
+         * is present in the layout. Otherwise it is not present.
+         *
+         * @note when a channel layout using a bitmask is constructed or
+         * modified manually (i.e.  not using any of the av_channel_layout_*
+         * functions), the code doing it must ensure that the number of set bits
+         * is equal to nb_channels.
+         */
+        uint64_t mask;
+        /**
+         * This member must be used when the channel order is
+         * AV_CHANNEL_ORDER_CUSTOM. It is a nb_channels-sized array, with each
+         * element signalling the presence of the AVChannel with the
+         * corresponding value in map[i].id.
+         *
+         * I.e. when map[i].id is equal to AV_CHAN_FOO, then AV_CH_FOO is the
+         * i-th channel in the audio data.
+         *
+         * map[i].name may be filled with a 0-terminated string, in which case
+         * it will be used for the purpose of identifying the channel with the
+         * convenience functions below. Otherise it must be zeroed.
+         */
+        AVChannelCustom *map;
+    } u;
+
+    /**
+     * For some private data of the user.
+     */
+    void *opaque;
+} AVChannelLayout;
+
+#define AV_CHANNEL_LAYOUT_MASK(nb, m) \
+    { .order = AV_CHANNEL_ORDER_NATIVE, .nb_channels = (nb), .u = { .mask = (m) }}
+
+#define AV_CHANNEL_LAYOUT_MONO              AV_CHANNEL_LAYOUT_MASK(1,  AV_CH_LAYOUT_MONO)
+#define AV_CHANNEL_LAYOUT_STEREO            AV_CHANNEL_LAYOUT_MASK(2,  AV_CH_LAYOUT_STEREO)
+#define AV_CHANNEL_LAYOUT_2POINT1           AV_CHANNEL_LAYOUT_MASK(3,  AV_CH_LAYOUT_2POINT1)
+#define AV_CHANNEL_LAYOUT_2_1               AV_CHANNEL_LAYOUT_MASK(3,  AV_CH_LAYOUT_2_1)
+#define AV_CHANNEL_LAYOUT_SURROUND          AV_CHANNEL_LAYOUT_MASK(3,  AV_CH_LAYOUT_SURROUND)
+#define AV_CHANNEL_LAYOUT_3POINT1           AV_CHANNEL_LAYOUT_MASK(4,  AV_CH_LAYOUT_3POINT1)
+#define AV_CHANNEL_LAYOUT_4POINT0           AV_CHANNEL_LAYOUT_MASK(4,  AV_CH_LAYOUT_4POINT0)
+#define AV_CHANNEL_LAYOUT_4POINT1           AV_CHANNEL_LAYOUT_MASK(5,  AV_CH_LAYOUT_4POINT1)
+#define AV_CHANNEL_LAYOUT_2_2               AV_CHANNEL_LAYOUT_MASK(4,  AV_CH_LAYOUT_2_2)
+#define AV_CHANNEL_LAYOUT_QUAD              AV_CHANNEL_LAYOUT_MASK(4,  AV_CH_LAYOUT_QUAD)
+#define AV_CHANNEL_LAYOUT_5POINT0           AV_CHANNEL_LAYOUT_MASK(5,  AV_CH_LAYOUT_5POINT0)
+#define AV_CHANNEL_LAYOUT_5POINT1           AV_CHANNEL_LAYOUT_MASK(6,  AV_CH_LAYOUT_5POINT1)
+#define AV_CHANNEL_LAYOUT_5POINT0_BACK      AV_CHANNEL_LAYOUT_MASK(5,  AV_CH_LAYOUT_5POINT0_BACK)
+#define AV_CHANNEL_LAYOUT_5POINT1_BACK      AV_CHANNEL_LAYOUT_MASK(6,  AV_CH_LAYOUT_5POINT1_BACK)
+#define AV_CHANNEL_LAYOUT_6POINT0           AV_CHANNEL_LAYOUT_MASK(6,  AV_CH_LAYOUT_6POINT0)
+#define AV_CHANNEL_LAYOUT_6POINT0_FRONT     AV_CHANNEL_LAYOUT_MASK(6,  AV_CH_LAYOUT_6POINT0_FRONT)
+#define AV_CHANNEL_LAYOUT_HEXAGONAL         AV_CHANNEL_LAYOUT_MASK(6,  AV_CH_LAYOUT_HEXAGONAL)
+#define AV_CHANNEL_LAYOUT_6POINT1           AV_CHANNEL_LAYOUT_MASK(7,  AV_CH_LAYOUT_6POINT1)
+#define AV_CHANNEL_LAYOUT_6POINT1_BACK      AV_CHANNEL_LAYOUT_MASK(7,  AV_CH_LAYOUT_6POINT1_BACK)
+#define AV_CHANNEL_LAYOUT_6POINT1_FRONT     AV_CHANNEL_LAYOUT_MASK(7,  AV_CH_LAYOUT_6POINT1_FRONT)
+#define AV_CHANNEL_LAYOUT_7POINT0           AV_CHANNEL_LAYOUT_MASK(7,  AV_CH_LAYOUT_7POINT0)
+#define AV_CHANNEL_LAYOUT_7POINT0_FRONT     AV_CHANNEL_LAYOUT_MASK(7,  AV_CH_LAYOUT_7POINT0_FRONT)
+#define AV_CHANNEL_LAYOUT_7POINT1           AV_CHANNEL_LAYOUT_MASK(8,  AV_CH_LAYOUT_7POINT1)
+#define AV_CHANNEL_LAYOUT_7POINT1_WIDE      AV_CHANNEL_LAYOUT_MASK(8,  AV_CH_LAYOUT_7POINT1_WIDE)
+#define AV_CHANNEL_LAYOUT_7POINT1_WIDE_BACK AV_CHANNEL_LAYOUT_MASK(8,  AV_CH_LAYOUT_7POINT1_WIDE_BACK)
+#define AV_CHANNEL_LAYOUT_OCTAGONAL         AV_CHANNEL_LAYOUT_MASK(8,  AV_CH_LAYOUT_OCTAGONAL)
+#define AV_CHANNEL_LAYOUT_HEXADECAGONAL     AV_CHANNEL_LAYOUT_MASK(16, AV_CH_LAYOUT_HEXADECAGONAL)
+#define AV_CHANNEL_LAYOUT_STEREO_DOWNMIX    AV_CHANNEL_LAYOUT_MASK(2,  AV_CH_LAYOUT_STEREO_DOWNMIX)
+#define AV_CHANNEL_LAYOUT_22POINT2          AV_CHANNEL_LAYOUT_MASK(24, AV_CH_LAYOUT_22POINT2)
+
+struct AVBPrint;
+
+#if FF_API_OLD_CHANNEL_LAYOUT
+/**
  * Return a channel layout id that matches name, or 0 if no match is found.
  *
  * name can be one or several of the following notations,
@@ -144,7 +353,10 @@ enum AVMatrixEncoding {
  *   AV_CH_* macros).
  *
  * Example: "stereo+FC" = "2c+FC" = "2c+1c" = "0x7"
+ *
+ * @deprecated use av_channel_layout_from_string()
  */
+attribute_deprecated
 uint64_t av_get_channel_layout(const char *name);
 
 /**
@@ -158,7 +370,9 @@ uint64_t av_get_channel_layout(const char *name);
  * @param[out] nb_channels      number of channels
  *
  * @return 0 on success, AVERROR(EINVAL) if the parsing fails.
+ * @deprecated use av_channel_layout_from_string()
  */
+attribute_deprecated
 int av_get_extended_channel_layout(const char *name, uint64_t* channel_layout, int* nb_channels);
 
 /**
@@ -167,23 +381,31 @@ int av_get_extended_channel_layout(const char *name, uint64_t* channel_layout, i
  *
  * @param buf put here the string containing the channel layout
  * @param buf_size size in bytes of the buffer
+ * @deprecated use av_channel_layout_describe()
  */
+attribute_deprecated
 void av_get_channel_layout_string(char *buf, int buf_size, int nb_channels, uint64_t channel_layout);
 
-struct AVBPrint;
 /**
  * Append a description of a channel layout to a bprint buffer.
+ * @deprecated use av_channel_layout_describe()
  */
+attribute_deprecated
 void av_bprint_channel_layout(struct AVBPrint *bp, int nb_channels, uint64_t channel_layout);
 
 /**
  * Return the number of channels in the channel layout.
+ * @deprecated use AVChannelLayout.nb_channels
  */
+attribute_deprecated
 int av_get_channel_layout_nb_channels(uint64_t channel_layout);
 
 /**
  * Return default channel layout for a given number of channels.
+ *
+ * @deprecated use av_channel_layout_default()
  */
+attribute_deprecated
 int64_t av_get_default_channel_layout(int nb_channels);
 
 /**
@@ -194,20 +416,28 @@ int64_t av_get_default_channel_layout(int nb_channels);
  *
  * @return index of channel in channel_layout on success, a negative AVERROR
  *         on error.
+ *
+ * @deprecated use av_channel_layout_index_from_channel()
  */
+attribute_deprecated
 int av_get_channel_layout_channel_index(uint64_t channel_layout,
                                         uint64_t channel);
 
 /**
  * Get the channel with the given index in channel_layout.
+ * @deprecated use av_channel_layout_channel_from_index()
  */
+attribute_deprecated
 uint64_t av_channel_layout_extract_channel(uint64_t channel_layout, int index);
 
 /**
  * Get the name of a given channel.
  *
  * @return channel name on success, NULL on error.
+ *
+ * @deprecated use av_channel_name()
  */
+attribute_deprecated
 const char *av_get_channel_name(uint64_t channel);
 
 /**
@@ -215,7 +445,9 @@ const char *av_get_channel_name(uint64_t channel);
  *
  * @param channel  a channel layout with a single channel
  * @return  channel description on success, NULL on error
+ * @deprecated use av_channel_description()
  */
+attribute_deprecated
 const char *av_get_channel_description(uint64_t channel);
 
 /**
@@ -226,9 +458,238 @@ const char *av_get_channel_description(uint64_t channel);
  * @param[out] name    name of the layout
  * @return  0  if the layout exists,
  *          <0 if index is beyond the limits
+ * @deprecated use av_channel_layout_standard()
  */
+attribute_deprecated
 int av_get_standard_channel_layout(unsigned index, uint64_t *layout,
                                    const char **name);
+#endif
+
+/**
+ * Get a human readable string in an abbreviated form describing a given channel.
+ * This is the inverse function of @ref av_channel_from_string().
+ *
+ * @param buf pre-allocated buffer where to put the generated string
+ * @param buf_size size in bytes of the buffer.
+ * @return amount of bytes needed to hold the output string, or a negative AVERROR
+ *         on failure. If the returned value is bigger than buf_size, then the
+ *         string was truncated.
+ */
+int av_channel_name(char *buf, size_t buf_size, enum AVChannel channel);
+
+/**
+ * bprint variant of av_channel_name().
+ *
+ * @note the string will be appended to the bprint buffer.
+ */
+void av_channel_name_bprint(struct AVBPrint *bp, enum AVChannel channel_id);
+
+/**
+ * Get a human readable string describing a given channel.
+ *
+ * @param buf pre-allocated buffer where to put the generated string
+ * @param buf_size size in bytes of the buffer.
+ * @return amount of bytes needed to hold the output string, or a negative AVERROR
+ *         on failure. If the returned value is bigger than buf_size, then the
+ *         string was truncated.
+ */
+int av_channel_description(char *buf, size_t buf_size, enum AVChannel channel);
+
+/**
+ * bprint variant of av_channel_description().
+ *
+ * @note the string will be appended to the bprint buffer.
+ */
+void av_channel_description_bprint(struct AVBPrint *bp, enum AVChannel channel_id);
+
+/**
+ * This is the inverse function of @ref av_channel_name().
+ *
+ * @return the channel with the given name
+ *         AV_CHAN_NONE when name does not identify a known channel
+ */
+enum AVChannel av_channel_from_string(const char *name);
+
+/**
+ * Initialize a native channel layout from a bitmask indicating which channels
+ * are present.
+ *
+ * @param channel_layout the layout structure to be initialized
+ * @param mask bitmask describing the channel layout
+ *
+ * @return 0 on success
+ *         AVERROR(EINVAL) for invalid mask values
+ */
+int av_channel_layout_from_mask(AVChannelLayout *channel_layout, uint64_t mask);
+
+/**
+ * Initialize a channel layout from a given string description.
+ * The input string can be represented by:
+ *  - the formal channel layout name (returned by av_channel_layout_describe())
+ *  - single or multiple channel names (returned by av_channel_name(), eg. "FL",
+ *    or concatenated with "+", each optionally containing a custom name after
+ *    a "@", eg. "FL@Left+FR@Right+LFE")
+ *  - a decimal or hexadecimal value of a native channel layout (eg. "4" or "0x4")
+ *  - the number of channels with default layout (eg. "4c")
+ *  - the number of unordered channels (eg. "4C" or "4 channels")
+ *
+ * @param channel_layout input channel layout
+ * @param str string describing the channel layout
+ * @return 0 channel layout was detected, AVERROR_INVALIDATATA otherwise
+ */
+int av_channel_layout_from_string(AVChannelLayout *channel_layout,
+                                  const char *str);
+
+/**
+ * Get the default channel layout for a given number of channels.
+ *
+ * @param channel_layout the layout structure to be initialized
+ * @param nb_channels number of channels
+ */
+void av_channel_layout_default(AVChannelLayout *ch_layout, int nb_channels);
+
+/**
+ * Iterate over all standard channel layouts.
+ *
+ * @param opaque a pointer where libavutil will store the iteration state. Must
+ *               point to NULL to start the iteration.
+ *
+ * @return the standard channel layout or NULL when the iteration is
+ *         finished
+ */
+const AVChannelLayout *av_channel_layout_standard(void **opaque);
+
+/**
+ * Free any allocated data in the channel layout and reset the channel
+ * count to 0.
+ *
+ * @param channel_layout the layout structure to be uninitialized
+ */
+void av_channel_layout_uninit(AVChannelLayout *channel_layout);
+
+/**
+ * Make a copy of a channel layout. This differs from just assigning src to dst
+ * in that it allocates and copies the map for AV_CHANNEL_ORDER_CUSTOM.
+ *
+ * @note the destination channel_layout will be always uninitialized before copy.
+ *
+ * @param dst destination channel layout
+ * @param src source channel layout
+ * @return 0 on success, a negative AVERROR on error.
+ */
+int av_channel_layout_copy(AVChannelLayout *dst, const AVChannelLayout *src);
+
+/**
+ * Get a human-readable string describing the channel layout properties.
+ * The string will be in the same format that is accepted by
+ * @ref av_channel_layout_from_string(), allowing to rebuild the same
+ * channel layout, except for opaque pointers.
+ *
+ * @param channel_layout channel layout to be described
+ * @param buf pre-allocated buffer where to put the generated string
+ * @param buf_size size in bytes of the buffer.
+ * @return amount of bytes needed to hold the output string, or a negative AVERROR
+ *         on failure. If the returned value is bigger than buf_size, then the
+ *         string was truncated.
+ */
+int av_channel_layout_describe(const AVChannelLayout *channel_layout,
+                               char *buf, size_t buf_size);
+
+/**
+ * bprint variant of av_channel_layout_describe().
+ *
+ * @note the string will be appended to the bprint buffer.
+ * @return 0 on success, or a negative AVERROR value on failure.
+ */
+int av_channel_layout_describe_bprint(const AVChannelLayout *channel_layout,
+                                      struct AVBPrint *bp);
+
+/**
+ * Get the channel with the given index in a channel layout.
+ *
+ * @param channel_layout input channel layout
+ * @return channel with the index idx in channel_layout on success or
+ *         AV_CHAN_NONE on failure (if idx is not valid or the channel order is
+ *         unspecified)
+ */
+enum AVChannel
+av_channel_layout_channel_from_index(const AVChannelLayout *channel_layout, unsigned int idx);
+
+/**
+ * Get the index of a given channel in a channel layout. In case multiple
+ * channels are found, only the first match will be returned.
+ *
+ * @param channel_layout input channel layout
+ * @return index of channel in channel_layout on success or a negative number if
+ *         channel is not present in channel_layout.
+ */
+int av_channel_layout_index_from_channel(const AVChannelLayout *channel_layout,
+                                         enum AVChannel channel);
+
+/**
+ * Get the index in a channel layout of a channel described by the given string.
+ * In case multiple channels are found, only the first match will be returned.
+ *
+ * This function accepts channel names in the same format as
+ * @ref av_channel_from_string().
+ *
+ * @param channel_layout input channel layout
+ * @return a channel index described by the given string, or a negative AVERROR
+ *         value.
+ */
+int av_channel_layout_index_from_string(const AVChannelLayout *channel_layout,
+                                        const char *name);
+
+/**
+ * Get a channel described by the given string.
+ *
+ * This function accepts channel names in the same format as
+ * @ref av_channel_from_string().
+ *
+ * @param channel_layout input channel layout
+ * @return a channel described by the given string in channel_layout on success
+ *         or AV_CHAN_NONE on failure (if the string is not valid or the channel
+ *         order is unspecified)
+ */
+enum AVChannel
+av_channel_layout_channel_from_string(const AVChannelLayout *channel_layout,
+                                      const char *name);
+
+/**
+ * Find out what channels from a given set are present in a channel layout,
+ * without regard for their positions.
+ *
+ * @param channel_layout input channel layout
+ * @param mask a combination of AV_CH_* representing a set of channels
+ * @return a bitfield representing all the channels from mask that are present
+ *         in channel_layout
+ */
+uint64_t av_channel_layout_subset(const AVChannelLayout *channel_layout,
+                                  uint64_t mask);
+
+/**
+ * Check whether a channel layout is valid, i.e. can possibly describe audio
+ * data.
+ *
+ * @param channel_layout input channel layout
+ * @return 1 if channel_layout is valid, 0 otherwise.
+ */
+int av_channel_layout_check(const AVChannelLayout *channel_layout);
+
+/**
+ * Check whether two channel layouts are semantically the same, i.e. the same
+ * channels are present on the same positions in both.
+ *
+ * If one of the channel layouts is AV_CHANNEL_ORDER_UNSPEC, while the other is
+ * not, they are considered to be unequal. If both are AV_CHANNEL_ORDER_UNSPEC,
+ * they are considered equal iff the channel counts are the same in both.
+ *
+ * @param chl input channel layout
+ * @param chl1 input channel layout
+ * @return 0 if chl and chl1 are equal, 1 if they are not equal. A negative
+ *         AVERROR code if one or both are invalid.
+ */
+int av_channel_layout_compare(const AVChannelLayout *chl, const AVChannelLayout *chl1);
 
 /**
  * @}