lavu: add AV_FRAME_DATA_DOWNMIX_INFO side data type.

doc/APIchanges

@@ -13,6 +13,10 @@ libavutil:     2013-12-xx
 
 API changes, most recent first:
 
+2014-02-xx - xxxxxxx - lavu 53.3.0 - frame.h
+  Add AV_FRAME_DATA_DOWNMIX_INFO value to the AVFrameSideDataType enum and
+  downmix_info.h API, which identify downmix-related metadata.
+
 2014-02-04 - d9ae103 - lavf 55.11.0 - avformat.h
   Add AVFormatContext.max_interleave_delta for controlling amount of buffering
   when interleaving.

libavutil/Makefile

@@ -16,6 +16,7 @@ HEADERS = adler32.h                                                     \
           common.h                                                      \
           cpu.h                                                         \
           crc.h                                                         \
+          downmix_info.h                                                \
           error.h                                                       \
           eval.h                                                        \
           fifo.h                                                        \
@@ -67,6 +68,7 @@ OBJS = adler32.o                                                        \
        cpu.o                                                            \
        crc.o                                                            \
        des.o                                                            \
+       downmix_info.o                                                   \
        error.o                                                          \
        eval.o                                                           \
        fifo.o                                                           \

libavutil/downmix_info.c

+/*
+ * Copyright (c) 2014 Tim Walker <tdskywalker@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "downmix_info.h"
+#include "frame.h"
+
+AVDownmixInfo *av_downmix_info_update_side_data(AVFrame *frame)
+{
+    AVFrameSideData *side_data;
+
+    side_data = av_frame_get_side_data(frame, AV_FRAME_DATA_DOWNMIX_INFO);
+
+    if (!side_data)
+        side_data = av_frame_new_side_data(frame, AV_FRAME_DATA_DOWNMIX_INFO,
+                                           sizeof(AVDownmixInfo));
+
+    if (!side_data)
+        return NULL;
+
+    return (AVDownmixInfo*)side_data->data;
+}

libavutil/downmix_info.h

+/*
+ * Copyright (c) 2014 Tim Walker <tdskywalker@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_DOWNMIX_INFO_H
+#define AVUTIL_DOWNMIX_INFO_H
+
+#include "frame.h"
+
+/**
+ * @file
+ * audio downmix medatata
+ */
+
+/**
+ * @addtogroup lavu_audio
+ * @{
+ */
+
+/**
+ * @defgroup downmix_info Audio downmix metadata
+ * @{
+ */
+
+/**
+ * Possible downmix types.
+ */
+enum AVDownmixType {
+    AV_DOWNMIX_TYPE_UNKNOWN, /**< Not indicated. */
+    AV_DOWNMIX_TYPE_LORO,    /**< Lo/Ro 2-channel downmix (Stereo). */
+    AV_DOWNMIX_TYPE_LTRT,    /**< Lt/Rt 2-channel downmix, Dolby Surround compatible. */
+    AV_DOWNMIX_TYPE_DPLII,   /**< Lt/Rt 2-channel downmix, Dolby Pro Logic II compatible. */
+    AV_DOWNMIX_TYPE_NB       /**< Number of downmix types. Not part of ABI. */
+};
+
+/**
+ * This structure describes optional metadata relevant to a downmix procedure.
+ *
+ * All fields are set by the decoder to the value indicated in the audio
+ * bitstream (if present), or to a "sane" default otherwise.
+ */
+typedef struct AVDownmixInfo {
+    /**
+     * Type of downmix preferred by the mastering engineer.
+     */
+    enum AVDownmixType preferred_downmix_type;
+
+    /**
+     * Absolute scale factor representing the nominal level of the center
+     * channel during a regular downmix.
+     */
+    double center_mix_level;
+
+    /**
+     * Absolute scale factor representing the nominal level of the center
+     * channel during an Lt/Rt compatible downmix.
+     */
+    double center_mix_level_ltrt;
+
+    /**
+     * Absolute scale factor representing the nominal level of the surround
+     * channels during a regular downmix.
+     */
+    double surround_mix_level;
+
+    /**
+     * Absolute scale factor representing the nominal level of the surround
+     * channels during an Lt/Rt compatible downmix.
+     */
+    double surround_mix_level_ltrt;
+
+    /**
+     * Absolute scale factor representing the level at which the LFE data is
+     * mixed into L/R channels during downmixing.
+     */
+    double lfe_mix_level;
+} AVDownmixInfo;
+
+/**
+ * Get a frame's AV_FRAME_DATA_DOWNMIX_INFO side data for editing.
+ *
+ * The side data is created and added to the frame if it's absent.
+ *
+ * @param frame the frame for which the side data is to be obtained.
+ *
+ * @return the AVDownmixInfo structure to be edited by the caller.
+ */
+AVDownmixInfo *av_downmix_info_update_side_data(AVFrame *frame);
+
+/**
+ * @}
+ */
+
+/**
+ * @}
+ */
+
+#endif /* AVUTIL_DOWNMIX_INFO_H */

libavutil/frame.h

@@ -64,6 +64,11 @@ enum AVFrameSideDataType {
      * The data is the AVMatrixEncoding enum defined in libavutil/channel_layout.h.
      */
     AV_FRAME_DATA_MATRIXENCODING,
+    /**
+     * Metadata relevant to a downmix procedure.
+     * The data is the AVDownmixInfo struct defined in libavutil/downmix_info.h.
+     */
+    AV_FRAME_DATA_DOWNMIX_INFO,
 };
 
 typedef struct AVFrameSideData {

libavutil/version.h

@@ -54,7 +54,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 53
-#define LIBAVUTIL_VERSION_MINOR  2
+#define LIBAVUTIL_VERSION_MINOR  3
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \