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diff --git a/libhb/handbrake/audio_remap.h b/libhb/handbrake/audio_remap.h
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+/* audio_remap.h
+ *
+ * Copyright (c) 2003-2019 HandBrake Team
+ * This file is part of the HandBrake source code
+ * Homepage: <http://handbrake.fr/>
+ * It may be used under the terms of the GNU General Public License v2.
+ * For full terms see the file COPYING file or visit http://www.gnu.org/licenses/gpl-2.0.html
+ */
+
+/* This file handles the following two scenarios:
+ *
+ * 1) remapping audio from decoder order to libav order (for downmixing)
+ *
+ * 2) remapping audio from libav order to encoder order (for encoding)
+ *
+ * We only need to support:
+ *
+ * a) channels found in our non-libavcodec audio decoders' layouts
+ * b) channels found in HB_AMIXDOWN_* layouts
+ *
+ * We consider that:
+ *
+ * Left/Right Surround == Side Left/Right
+ * Left/Right Rear Surround == Back Left/Right */
+
+#ifndef AUDIO_REMAP_H
+#define AUDIO_REMAP_H
+
+#include <stdint.h>
+#include "libavutil/samplefmt.h"
+
+/* we only need to support the 11 "most common" channels */
+#define HB_AUDIO_REMAP_MAX_CHANNELS 11
+
+typedef struct
+{
+    uint64_t channel_order_map[HB_AUDIO_REMAP_MAX_CHANNELS + 1];
+} hb_chan_map_t;
+
+typedef struct
+{
+    int nchannels;
+    int remap_needed;
+    hb_chan_map_t *channel_map_in;
+    hb_chan_map_t *channel_map_out;
+    int table[HB_AUDIO_REMAP_MAX_CHANNELS];
+
+    void (*remap)(uint8_t **samples, int nsamples,
+                  int nchannels, int *remap_table);
+} hb_audio_remap_t;
+
+/*
+ * Predefined channel maps for common channel orders.
+ */
+extern hb_chan_map_t hb_libav_chan_map;
+extern hb_chan_map_t hb_liba52_chan_map;
+extern hb_chan_map_t hb_vorbis_chan_map;
+extern hb_chan_map_t hb_aac_chan_map;
+
+/*
+ * Initialize an hb_audio_remap_t to remap audio with the specified sample
+ * format, from the input to the output channel order (indicated by
+ * channel_map_in and channel_map_out, respectively).
+ */
+hb_audio_remap_t* hb_audio_remap_init(enum AVSampleFormat sample_fmt,
+                                      hb_chan_map_t *channel_map_out,
+                                      hb_chan_map_t *channel_map_in);
+
+/*
+ * Updates an hb_audio_remap_t's number of channels and remap table to work with
+ * the specified channel layout.
+ *
+ * Must be called at least once before remapping.
+ */
+void              hb_audio_remap_set_channel_layout(hb_audio_remap_t *remap,
+                                                    uint64_t channel_layout);
+
+/*
+ * Free an hb_audio_remap_t.
+ */
+void              hb_audio_remap_free(hb_audio_remap_t *remap);
+
+/*
+ * Remap audio between 2 different channel orders, using the settings specified
+ * in the remap parameter. Remapping is only done when necessary.
+ *
+ * The remap parameter can be NULL (no remapping).
+ */
+void              hb_audio_remap(hb_audio_remap_t *remap, uint8_t **samples,
+                                 int nsamples);
+
+/*
+ * Generate a table used to remap audio between 2 different channel orders.
+ *
+ * Usage: output_sample[channel_idx] = input_sample[remap_table[channel_idx]]
+ *
+ * remap_table is allocated by the caller.
+ */
+void              hb_audio_remap_build_table(hb_chan_map_t *channel_map_out,
+                                             hb_chan_map_t *channel_map_in,
+                                             uint64_t channel_layout,
+                                             int *remap_table);
+
+#endif /* AUDIO_REMAP_H */