MCL/sf/mw/gstreamer: comparison gst_plugins_base/gst-libs/gst/audio/multichannel.c

equal deleted inserted replaced

--1:000000000000
+:0e761a78d257
+/*
+* Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of "Eclipse Public License v1.0"
+* which accompanies this distribution, and is available
+* at the URL "http://www.eclipse.org/legal/epl-v10.html".
+*
+* Initial Contributors:
+* Nokia Corporation - initial contribution.
+*
+* Contributors:
+*
+* Description:
+*
+*/
+/* GStreamer Multichannel-Audio helper functions
+* (c) 2004 Ronald Bultje <rbultje@ronald.bitfreak.net>
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Library General Public
+* License as published by the Free Software Foundation; either
+* version 2 of the License, or (at your option) any later version.
+*
+* This library 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
+* Library General Public License for more details.
+*
+* You should have received a copy of the GNU Library General Public
+* License along with this library; if not, write to the
+* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+* Boston, MA 02111-1307, USA.
+*/
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include "multichannel.h"
+#define GST_AUDIO_CHANNEL_POSITIONS_FIELD_NAME "channel-positions"
+/*
+* This function checks if basic assumptions apply:
+*  - does each position occur at most once?
+*  - do conflicting positions occur?
+*     + front_mono vs. front_left/right
+*     + front_center vs. front_left/right_of_center
+*     + rear_center vs. rear_left/right
+* It also adds some hacks that 0.8.x needs for compatibility:
+*  - if channels == 1, are we really mono?
+*  - if channels == 2, are we really stereo?
+*/
+static gboolean
+gst_audio_check_channel_positions (const GstAudioChannelPosition * pos,
+gint channels)
+{
+gint i, n;
+const struct
+{
+const GstAudioChannelPosition pos1[2];
+const GstAudioChannelPosition pos2[1];
+} conf[] = {
+/* front: mono <-> stereo */
+{ {
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT}, {
+GST_AUDIO_CHANNEL_POSITION_FRONT_MONO}},
+/* front center: 2 <-> 1 */
+{ {
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT_OF_CENTER}, {
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER}},
+/* rear: 2 <-> 1 */
+{ {
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT}, {
+GST_AUDIO_CHANNEL_POSITION_REAR_CENTER}}, { {
+GST_AUDIO_CHANNEL_POSITION_INVALID}}
+};
+g_assert (pos != NULL && channels > 0);
+/* check for invalid channel positions */
+for (n = 0; n < channels; n++) {
+if (pos[n] <= GST_AUDIO_CHANNEL_POSITION_INVALID ||
+pos[n] >= GST_AUDIO_CHANNEL_POSITION_NUM) {
+g_warning ("Channel position %d for channel %d is invalid", pos[n], n);
+return FALSE;
+}
+}
+/* either all channel positions are NONE or all are defined,
+* but having only some channel positions NONE and others not
+* is not allowed */
+if (pos[0] == GST_AUDIO_CHANNEL_POSITION_NONE) {
+for (n = 1; n < channels; ++n) {
+if (pos[n] != GST_AUDIO_CHANNEL_POSITION_NONE) {
+g_warning ("Either all channel positions must be defined, or all "
+"be set to NONE, having only some defined is not allowed");
+return FALSE;
+}
+}
+/* all positions are NONE, we are done here */
+return TRUE;
+}
+/* check for multiple position occurrences */
+for (i = GST_AUDIO_CHANNEL_POSITION_INVALID + 1;
+i < GST_AUDIO_CHANNEL_POSITION_NUM; i++) {
+gint count = 0;
+for (n = 0; n < channels; n++) {
+if (pos[n] == i)
+count++;
+}
+/* NONE may not occur mixed with other channel positions */
+if (i == GST_AUDIO_CHANNEL_POSITION_NONE && count > 0) {
+g_warning ("Either all channel positions must be defined, or all "
+"be set to NONE, having only some defined is not allowed");
+return FALSE;
+}
+if (count > 1) {
+g_warning ("Channel position %d occurred %d times, not allowed",
+i, count);
+return FALSE;
+}
+}
+/* check for position conflicts */
+for (i = 0; conf[i].pos1[0] != GST_AUDIO_CHANNEL_POSITION_INVALID; i++) {
+gboolean found1 = FALSE, found2 = FALSE;
+for (n = 0; n < channels; n++) {
+if (pos[n] == conf[i].pos1[0] || pos[n] == conf[i].pos1[1])
+found1 = TRUE;
+else if (pos[n] == conf[i].pos2[0])
+found2 = TRUE;
+}
+if (found1 && found2) {
+g_warning ("Found conflicting channel positions %d/%d and %d",
+conf[i].pos1[0], conf[i].pos1[1], conf[i].pos2[0]);
+return FALSE;
+}
+}
+/* Throw warning if we encounter an unusual 2-channel configuration,
+* at least until someone finds a reason why we should not */
+if (channels == 2 && (pos[0] != GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT ||
+pos[1] != GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT)) {
+g_warning ("channels=2 implies stereo, but channel positions are "
+"< %d, %d>", pos[0], pos[1]);
+return FALSE;
+}
+return TRUE;
+}
+/* FIXME: these default positions may or may not be correct. In any
+* case, they are mostly just a fallback for buggy plugins, so it
+* should not really matter too much */
+#define NUM_DEF_CHANS  8
+static const GstAudioChannelPosition
+default_positions[NUM_DEF_CHANS][NUM_DEF_CHANS] = {
+/* 1 channel */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_MONO,
+},
+/* 2 channels */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+},
+/* 3 channels (2.1) */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_LFE, /* or FRONT_CENTER for 3.0? */
+},
+/* 4 channels (4.0 or 3.1?) */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
+},
+/* 5 channels */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER,
+},
+/* 6 channels */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER,
+GST_AUDIO_CHANNEL_POSITION_LFE,
+},
+/* 7 channels */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER,
+GST_AUDIO_CHANNEL_POSITION_LFE,
+GST_AUDIO_CHANNEL_POSITION_REAR_CENTER,
+},
+/* 8 channels */
+{
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER,
+GST_AUDIO_CHANNEL_POSITION_LFE,
+GST_AUDIO_CHANNEL_POSITION_SIDE_LEFT,
+GST_AUDIO_CHANNEL_POSITION_SIDE_RIGHT,
+}
+};
+/**
+* gst_audio_get_channel_positions:
+* @str: A #GstStructure to retrieve channel positions from.
+*
+* Retrieves a number of (fixed!) audio channel positions from
+* the provided #GstStructure and returns it as a newly allocated
+* array. The caller should g_free () this array. The caller
+* should also check that the members in this #GstStructure are
+* indeed "fixed" before calling this function.
+*
+* Returns: a newly allocated array containing the channel
+* positions as provided in the given #GstStructure. Returns
+* NULL on error.
+*/
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+GstAudioChannelPosition *
+gst_audio_get_channel_positions (GstStructure * str)
+{
+GstAudioChannelPosition *pos;
+gint channels, n;
+const GValue *pos_val_arr, *pos_val_entry;
+gboolean res;
+GType t;
+/* get number of channels, general type checkups */
+g_return_val_if_fail (str != NULL, NULL);
+res = gst_structure_get_int (str, "channels", &channels);
+g_return_val_if_fail (res, NULL);
+g_return_val_if_fail (channels > 0, NULL);
+pos_val_arr = gst_structure_get_value (str,
+GST_AUDIO_CHANNEL_POSITIONS_FIELD_NAME);
+/* The following checks are here to retain compatibility for plugins not
+* implementing this field. They expect that channels=1 implies mono
+* and channels=2 implies stereo, so we follow that. */
+if (pos_val_arr == NULL) {
+/* channel layouts for 1 and 2 channels are implicit, don't warn */
+if (channels > 2) {
+g_warning ("Failed to retrieve channel layout from caps. This usually "
+"means there is a GStreamer element that does not implement "
+"multichannel audio correctly. Please file a bug.");
+}
+/* just return some default channel layout if we have one */
+if (channels >= 1 && channels <= NUM_DEF_CHANS) {
+const GstAudioChannelPosition *p;
+p = default_positions[channels - 1];
+return g_memdup (p, channels * sizeof (GstAudioChannelPosition));
+}
+return NULL;
+}
+g_return_val_if_fail (gst_value_array_get_size (pos_val_arr) == channels,
+NULL);
+for (n = 0; n < channels; n++) {
+t = G_VALUE_TYPE (gst_value_array_get_value (pos_val_arr, n));
+g_return_val_if_fail (t == GST_TYPE_AUDIO_CHANNEL_POSITION, NULL);
+}
+/* ... and fill array */
+pos = g_new (GstAudioChannelPosition, channels);
+for (n = 0; n < channels; n++) {
+pos_val_entry = gst_value_array_get_value (pos_val_arr, n);
+pos[n] = g_value_get_enum (pos_val_entry);
+}
+if (!gst_audio_check_channel_positions (pos, channels)) {
+g_free (pos);
+return NULL;
+}
+return pos;
+}
+/**
+* gst_audio_set_channel_positions:
+* @str: A #GstStructure to set channel positions on.
+* @pos: an array of channel positions. The number of members
+*       in this array should be equal to the (fixed!) number
+*       of the "channels" field in the given #GstStructure.
+*
+* Adds a "channel-positions" field to the given #GstStructure,
+* which will represent the channel positions as given in the
+* provided #GstAudioChannelPosition array.
+*/
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+void
+gst_audio_set_channel_positions (GstStructure * str,
+const GstAudioChannelPosition * pos)
+{
+GValue pos_val_arr = { 0 }, pos_val_entry = {
+0};
+gint channels, n;
+gboolean res;
+/* get number of channels, checkups */
+g_return_if_fail (str != NULL);
+g_return_if_fail (pos != NULL);
+res = gst_structure_get_int (str, "channels", &channels);
+g_return_if_fail (res);
+g_return_if_fail (channels > 0);
+if (!gst_audio_check_channel_positions (pos, channels))
+return;
+/* build gvaluearray from positions */
+g_value_init (&pos_val_entry, GST_TYPE_AUDIO_CHANNEL_POSITION);
+g_value_init (&pos_val_arr, GST_TYPE_ARRAY);
+for (n = 0; n < channels; n++) {
+g_value_set_enum (&pos_val_entry, pos[n]);
+gst_value_array_append_value (&pos_val_arr, &pos_val_entry);
+}
+g_value_unset (&pos_val_entry);
+/* add to structure */
+gst_structure_set_value (str,
+GST_AUDIO_CHANNEL_POSITIONS_FIELD_NAME, &pos_val_arr);
+g_value_unset (&pos_val_arr);
+}
+/**
+* gst_audio_set_structure_channel_positions_list:
+* @str: #GstStructure to set the list of channel positions
+*       on.
+* @pos: the array containing one or more possible audio
+*       channel positions that we should add in each value
+*       of the array in the given structure.
+* @num_positions: the number of values in pos.
+*
+* Sets a (possibly non-fixed) list of possible audio channel
+* positions (given in pos) on the given structure. The
+* structure, after this function has been called, will contain
+* a "channel-positions" field with an array of the size of
+* the "channels" field value in the given structure (note
+* that this means that the channels field in the provided
+* structure should be fixed!). Each value in the array will
+* contain each of the values given in the pos array.
+*/
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+void
+gst_audio_set_structure_channel_positions_list (GstStructure * str,
+const GstAudioChannelPosition * pos, gint num_positions)
+{
+gint channels, n, c;
+GValue pos_val_arr = { 0 }, pos_val_list = {
+0}, pos_val_entry = {
+0};
+gboolean res;
+/* get number of channels, general type checkups */
+g_return_if_fail (str != NULL);
+g_return_if_fail (num_positions > 0);
+g_return_if_fail (pos != NULL);
+res = gst_structure_get_int (str, "channels", &channels);
+g_return_if_fail (res);
+g_return_if_fail (channels > 0);
+/* 0.8.x: channels=1 or channels=2 is mono/stereo, no positions needed
+* there (we discard them anyway) */
+if (channels == 1 || channels == 2)
+return;
+/* create the array of lists */
+g_value_init (&pos_val_arr, GST_TYPE_ARRAY);
+g_value_init (&pos_val_entry, GST_TYPE_AUDIO_CHANNEL_POSITION);
+for (n = 0; n < channels; n++) {
+g_value_init (&pos_val_list, GST_TYPE_LIST);
+for (c = 0; c < num_positions; c++) {
+g_value_set_enum (&pos_val_entry, pos[c]);
+gst_value_list_append_value (&pos_val_list, &pos_val_entry);
+}
+gst_value_array_append_value (&pos_val_arr, &pos_val_list);
+g_value_unset (&pos_val_list);
+}
+g_value_unset (&pos_val_entry);
+gst_structure_set_value (str, GST_AUDIO_CHANNEL_POSITIONS_FIELD_NAME,
+&pos_val_arr);
+g_value_unset (&pos_val_arr);
+}
+/*
+* Helper function for below. The structure will be conserved,
+* but might be cut down. Any additional structures that were
+* created will be stored in the returned caps.
+*/
+static GstCaps *
+add_list_to_struct (GstStructure * str,
+const GstAudioChannelPosition * pos, gint num_positions)
+{
+GstCaps *caps = gst_caps_new_empty ();
+const GValue *chan_val;
+chan_val = gst_structure_get_value (str, "channels");
+if (G_VALUE_TYPE (chan_val) == G_TYPE_INT) {
+gst_audio_set_structure_channel_positions_list (str, pos, num_positions);
+} else if (G_VALUE_TYPE (chan_val) == GST_TYPE_LIST) {
+gint size;
+const GValue *sub_val;
+size = gst_value_list_get_size (chan_val);
+sub_val = gst_value_list_get_value (chan_val, 0);
+gst_structure_set_value (str, "channels", sub_val);
+gst_caps_append (caps, add_list_to_struct (str, pos, num_positions));
+while (--size > 0) {
+str = gst_structure_copy (str);
+sub_val = gst_value_list_get_value (chan_val, size);
+gst_structure_set_value (str, "channels", sub_val);
+gst_caps_append (caps, add_list_to_struct (str, pos, num_positions));
+gst_caps_append_structure (caps, str);
+}
+} else if (G_VALUE_TYPE (chan_val) == GST_TYPE_INT_RANGE) {
+gint min, max;
+min = gst_value_get_int_range_min (chan_val);
+max = gst_value_get_int_range_max (chan_val);
+gst_structure_set (str, "channels", G_TYPE_INT, min, NULL);
+gst_audio_set_structure_channel_positions_list (str, pos, num_positions);
+for (++min; min < max; min++) {
+str = gst_structure_copy (str);
+gst_structure_set (str, "channels", G_TYPE_INT, min, NULL);
+gst_audio_set_structure_channel_positions_list (str, pos, num_positions);
+gst_caps_append_structure (caps, str);
+}
+} else {
+g_warning ("Unexpected value type '%s' for channels field",
+GST_STR_NULL (g_type_name (G_VALUE_TYPE (chan_val))));
+}
+return caps;
+}
+/**
+* gst_audio_set_caps_channel_positions_list:
+* @caps: #GstCaps to set the list of channel positions on.
+* @pos: the array containing one or more possible audio
+*       channel positions that we should add in each value
+*       of the array in the given structure.
+* @num_positions: the number of values in pos.
+*
+* Sets a (possibly non-fixed) list of possible audio channel
+* positions (given in pos) on the given caps. Each of the
+* structures of the caps, after this function has been called,
+* will contain a "channel-positions" field with an array.
+* Each value in the array will contain each of the values given
+* in the pos array. Note that the size of the caps might be
+* increased by this, since each structure with a "channel-
+* positions" field needs to have a fixed "channels" field.
+* The input caps is not required to have this.
+*/
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+void
+gst_audio_set_caps_channel_positions_list (GstCaps * caps,
+const GstAudioChannelPosition * pos, gint num_positions)
+{
+gint size, n;
+/* get number of channels, general type checkups */
+g_return_if_fail (caps != NULL);
+g_return_if_fail (num_positions > 0);
+g_return_if_fail (pos != NULL);
+size = gst_caps_get_size (caps);
+for (n = 0; n < size; n++) {
+gst_caps_append (caps, add_list_to_struct (gst_caps_get_structure (caps,
+n), pos, num_positions));
+}
+}
+/**
+* gst_audio_fixate_channel_positions:
+* @str: a #GstStructure containing a (possibly unfixed)
+*       "channel-positions" field.
+*
+* Custom fixate function. Elements that implement some sort of
+* channel conversion algorithm should use this function for
+* fixating on GstAudioChannelPosition properties. It will take
+* care of equal channel positioning (left/right). Caller g_free()s
+* the return value. The input properties may be (and are supposed
+* to be) unfixed.
+* Note that this function is mostly a hack because we currently
+* have no way to add default fixation functions for new GTypes.
+*
+* Returns: fixed values that the caller could use as a fixed
+* set of #GstAudioChannelPosition values.
+*/
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+GstAudioChannelPosition *
+gst_audio_fixate_channel_positions (GstStructure * str)
+{
+GstAudioChannelPosition *pos;
+gint channels, n, num_unfixed = 0, i, c;
+const GValue *pos_val_arr, *pos_val_entry, *pos_val;
+gboolean res, is_stereo = TRUE;
+GType t;
+/*
+* We're going to do this cluelessly. We'll make an array of values that
+* conflict with each other and, for each iteration in this array, pick
+* either one until all unknown values are filled. This might not work in
+* corner cases but should work OK for the general case.
+*/
+const struct
+{
+const GstAudioChannelPosition pos1[2];
+const GstAudioChannelPosition pos2[1];
+} conf[] = {
+/* front: mono <-> stereo */
+{ {
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT}, {
+GST_AUDIO_CHANNEL_POSITION_FRONT_MONO}},
+/* front center: 2 <-> 1 */
+{ {
+GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER,
+GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT_OF_CENTER}, {
+GST_AUDIO_CHANNEL_POSITION_FRONT_CENTER}},
+/* rear: 2 <-> 1 */
+{ {
+GST_AUDIO_CHANNEL_POSITION_REAR_LEFT,
+GST_AUDIO_CHANNEL_POSITION_REAR_RIGHT}, {
+GST_AUDIO_CHANNEL_POSITION_REAR_CENTER}}, { {
+GST_AUDIO_CHANNEL_POSITION_INVALID, GST_AUDIO_CHANNEL_POSITION_INVALID}, {
+GST_AUDIO_CHANNEL_POSITION_LFE}}, { {
+GST_AUDIO_CHANNEL_POSITION_SIDE_LEFT,
+GST_AUDIO_CHANNEL_POSITION_SIDE_RIGHT}, {
+GST_AUDIO_CHANNEL_POSITION_INVALID}}, { {
+GST_AUDIO_CHANNEL_POSITION_INVALID, GST_AUDIO_CHANNEL_POSITION_INVALID}, {
+GST_AUDIO_CHANNEL_POSITION_INVALID}}
+};
+struct
+{
+gint num_opt[3];
+guint num_opts[3];
+gboolean is_fixed[3];
+gint choice;                /* -1 is none, 0 is the two, 1 is the one */
+} opt;
+/* get number of channels, general type checkups */
+g_return_val_if_fail (str != NULL, NULL);
+res = gst_structure_get_int (str, "channels", &channels);
+g_return_val_if_fail (res, NULL);
+g_return_val_if_fail (channels > 0, NULL);
+/* 0.8.x mono/stereo checks */
+pos_val_arr = gst_structure_get_value (str,
+GST_AUDIO_CHANNEL_POSITIONS_FIELD_NAME);
+if (!pos_val_arr && (channels == 1 || channels == 2)) {
+pos = g_new (GstAudioChannelPosition, channels);
+if (channels == 1) {
+pos[0] = GST_AUDIO_CHANNEL_POSITION_FRONT_MONO;
+} else {
+pos[0] = GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT;
+pos[1] = GST_AUDIO_CHANNEL_POSITION_FRONT_RIGHT;
+}
+return pos;
+}
+g_return_val_if_fail (pos_val_arr != NULL, NULL);
+g_return_val_if_fail (gst_value_array_get_size (pos_val_arr) == channels,
+NULL);
+for (n = 0; n < channels; n++) {
+t = G_VALUE_TYPE (gst_value_array_get_value (pos_val_arr, n));
+g_return_val_if_fail (t == GST_TYPE_LIST ||
+t == GST_TYPE_AUDIO_CHANNEL_POSITION, NULL);
+}
+/* all unknown, to start with */
+pos = g_new (GstAudioChannelPosition, channels);
+for (n = 0; n < channels; n++)
+pos[n] = GST_AUDIO_CHANNEL_POSITION_INVALID;
+num_unfixed = channels;
+/* Iterate the array of conflicting values */
+for (i = 0; conf[i].pos1[0] != GST_AUDIO_CHANNEL_POSITION_INVALID ||
+conf[i].pos2[0] != GST_AUDIO_CHANNEL_POSITION_INVALID; i++) {
+/* front/center only important if not mono (obviously) */
+if (conf[i].pos1[0] == GST_AUDIO_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER &&
+!is_stereo)
+continue;
+/* init values */
+for (n = 0; n < 3; n++) {
+opt.num_opt[n] = -1;
+opt.num_opts[n] = -1;
+opt.is_fixed[n] = FALSE;
+}
+/* Now, we'll see for each channel if it allows for any of the values in
+* the set of conflicting audio channel positions and keep scores. */
+for (n = 0; n < channels; n++) {
+/* if the channel is already taken, don't bother */
+if (pos[n] != GST_AUDIO_CHANNEL_POSITION_INVALID)
+continue;
+pos_val_entry = gst_value_array_get_value (pos_val_arr, n);
+t = G_VALUE_TYPE (pos_val_entry);
+if (t == GST_TYPE_LIST) {
+/* This algorhythm is suboptimal. */
+for (c = 0; c < gst_value_list_get_size (pos_val_entry); c++) {
+pos_val = gst_value_list_get_value (pos_val_entry, c);
+if (g_value_get_enum (pos_val) == conf[i].pos1[0] &&
+opt.num_opts[0] > gst_value_list_get_size (pos_val_entry) &&
+!opt.is_fixed[0]) {
+/* Now test if the old position of num_opt[0] also allows for
+* the other channel (which was skipped previously). If so,
+* keep score. */
+if (opt.num_opt[0] != -1) {
+gint c1;
+pos_val_entry = gst_value_array_get_value (pos_val_arr,
+opt.num_opt[0]);
+if (G_VALUE_TYPE (pos_val_entry) == GST_TYPE_LIST) {
+for (c1 = 0; c1 < gst_value_list_get_size (pos_val_entry); c1++) {
+pos_val = gst_value_list_get_value (pos_val_entry, c1);
+if (g_value_get_enum (pos_val) == conf[i].pos1[1] &&
+opt.num_opts[1] > opt.num_opts[0] && !opt.is_fixed[1]) {
+opt.num_opts[1] = opt.num_opts[0];
+opt.num_opt[1] = opt.num_opt[0];
+}
+}
+pos_val = gst_value_list_get_value (pos_val_entry, c);
+}
+pos_val_entry = gst_value_array_get_value (pos_val_arr, n);
+}
+/* and save values */
+opt.num_opts[0] = gst_value_list_get_size (pos_val_entry);
+opt.num_opt[0] = n;
+} else if (g_value_get_enum (pos_val) == conf[i].pos1[1] &&
+opt.num_opts[1] > gst_value_list_get_size (pos_val_entry) &&
+!opt.is_fixed[1] && n != opt.num_opt[0]) {
+opt.num_opts[1] = gst_value_list_get_size (pos_val_entry);
+opt.num_opt[1] = n;
+}
+/* 2 goes separately, because 0/1 vs. 2 are separate */
+if (g_value_get_enum (pos_val) == conf[i].pos2[0] &&
+opt.num_opts[2] > gst_value_list_get_size (pos_val_entry) &&
+!opt.is_fixed[2]) {
+opt.num_opts[2] = gst_value_list_get_size (pos_val_entry);
+opt.num_opt[2] = n;
+}
+}
+} else {
+if (g_value_get_enum (pos_val_entry) == conf[i].pos1[0]) {
+opt.num_opt[0] = n;
+opt.is_fixed[0] = TRUE;
+} else if (g_value_get_enum (pos_val_entry) == conf[i].pos1[1]) {
+opt.num_opt[1] = n;
+opt.is_fixed[1] = TRUE;
+} else if (g_value_get_enum (pos_val_entry) == conf[i].pos2[0]) {
+opt.num_opt[2] = n;
+opt.is_fixed[2] = TRUE;
+}
+}
+}
+/* check our results and choose either one */
+if ((opt.is_fixed[0] || opt.is_fixed[1]) && opt.is_fixed[2]) {
+g_warning ("Pre-fixated on both %d/%d and %d - conflict!",
+conf[i].pos1[0], conf[i].pos1[1], conf[i].pos2[0]);
+g_free (pos);
+return NULL;
+} else if ((opt.is_fixed[0] && opt.num_opt[1] == -1) ||
+(opt.is_fixed[1] && opt.num_opt[0] == -1)) {
+g_warning ("Pre-fixated one side, but other side n/a of %d/%d",
+conf[i].pos1[0], conf[i].pos1[1]);
+g_free (pos);
+return NULL;
+} else if (opt.is_fixed[0] || opt.is_fixed[1]) {
+opt.choice = 0;
+} else if (opt.is_fixed[2]) {
+opt.choice = 1;
+} else if (opt.num_opt[0] != -1 && opt.num_opt[1] != -1) {
+opt.choice = 0;
+} else if (opt.num_opt[2] != -1) {
+opt.choice = 1;
+} else {
+opt.choice = -1;
+}
+/* stereo? Note that we keep is_stereo to TRUE if we didn't decide on
+* any arrangement. The mono/stereo channels might be handled elsewhere
+* which is clearly outside the scope of this element, so we cannot
+* know and expect the application to handle that then. */
+if (conf[i].pos2[0] == GST_AUDIO_CHANNEL_POSITION_FRONT_MONO &&
+opt.choice == 1) {
+is_stereo = FALSE;
+}
+/* now actually decide what we'll do and fixate on that */
+if (opt.choice == 0) {
+g_assert (conf[i].pos1[0] != GST_AUDIO_CHANNEL_POSITION_INVALID &&
+conf[i].pos1[1] != GST_AUDIO_CHANNEL_POSITION_INVALID);
+pos[opt.num_opt[0]] = conf[i].pos1[0];
+pos[opt.num_opt[1]] = conf[i].pos1[1];
+num_unfixed -= 2;
+} else if (opt.choice == 1) {
+g_assert (conf[i].pos2[0] != GST_AUDIO_CHANNEL_POSITION_INVALID);
+pos[opt.num_opt[2]] = conf[i].pos2[0];
+num_unfixed--;
+}
+}
+/* safety check */
+if (num_unfixed > 0) {
+g_warning ("%d unfixed channel positions left after fixation!",
+num_unfixed);
+g_free (pos);
+return NULL;
+}
+if (!gst_audio_check_channel_positions (pos, channels)) {
+g_free (pos);
+return NULL;
+}
+return pos;
+}