From 59d58b3390cf866a5db6d3cd3908922d2905de6e Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Mon, 28 May 2012 12:20:57 +0200
Subject: [PATCH] audioconvert: add a function for extracting the channel with
 the given index

---
 libavutil/audioconvert.c | 14 ++++++++++++++
 libavutil/audioconvert.h |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/libavutil/audioconvert.c b/libavutil/audioconvert.c
index 36d07ee5a4..1ac63a37a6 100644
--- a/libavutil/audioconvert.c
+++ b/libavutil/audioconvert.c
@@ -213,3 +213,17 @@ const char *av_get_channel_name(uint64_t channel)
             return get_channel_name(i);
     return NULL;
 }
+
+uint64_t av_channel_layout_extract_channel(uint64_t channel_layout, int index)
+{
+    int i;
+
+    if (av_get_channel_layout_nb_channels(channel_layout) <= index)
+        return 0;
+
+    for (i = 0; i < 64; i++) {
+        if ((1ULL << i) & channel_layout && !index--)
+            return 1ULL << i;
+    }
+    return 0;
+}
diff --git a/libavutil/audioconvert.h b/libavutil/audioconvert.h
index e516ae8296..691c64a9de 100644
--- a/libavutil/audioconvert.h
+++ b/libavutil/audioconvert.h
@@ -155,6 +155,11 @@ uint64_t av_get_default_channel_layout(int nb_channels);
 int av_get_channel_layout_channel_index(uint64_t channel_layout,
                                         uint64_t channel);
 
+/**
+ * Get the channel with the given index in channel_layout.
+ */
+uint64_t av_channel_layout_extract_channel(uint64_t channel_layout, int index);
+
 /**
  * Get the name of a given channel.
  *