avutil/channel_layout: add av_get_extended_channel_layout

Return a channel layout and the number of channels based on the specified name.

This function is similar to av_get_channel_layout(), but can also parse unknown
channel layout specifications.

Unknown channel layout specifications are a decimal number and a capital 'C'
suffix, in order to not break compatibility with the lowercase 'c' suffix,
which is used for a guessed channel layout with the specified number of
channels.

Signed-off-by: Marton Balint <cus@passwd.hu>

1 files changed, 22 insertions, 0 deletions

diff --git a/libavutil/channel_layout.c b/libavutil/channel_layout.c
index 26c87c96a8..3bd5ee29b7 100644
--- a/libavutil/channel_layout.c
+++ b/libavutil/channel_layout.c
@@ -152,6 +152,28 @@ uint64_t av_get_channel_layout(const char *name)
     return layout;
 }
 
+int av_get_extended_channel_layout(const char *name, uint64_t* channel_layout, int* nb_channels)
+{
+    int nb = 0;
+    char *end;
+    uint64_t layout = av_get_channel_layout(name);
+
+    if (layout) {
+        *channel_layout = layout;
+        *nb_channels = av_get_channel_layout_nb_channels(layout);
+        return 0;
+    }
+
+    nb = strtol(name, &end, 10);
+    if (!errno && *end  == 'C' && *(end + 1) == '\0' && nb > 0 && nb < 64) {
+        *channel_layout = 0;
+        *nb_channels = nb;
+        return 0;
+    }
+
+    return AVERROR(EINVAL);
+}
+
 void av_bprint_channel_layout(struct AVBPrint *bp,
                               int nb_channels, uint64_t channel_layout)
 {