g726dec: set channel layout at initialization instead of validating it

libavcodec/g726.c

@@ -22,6 +22,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include <limits.h>
+
+#include "libavutil/audioconvert.h"
 #include "libavutil/avassert.h"
 #include "libavutil/opt.h"
 #include "avcodec.h"
@@ -428,10 +430,8 @@ static av_cold int g726_decode_init(AVCodecContext *avctx)
         return AVERROR(EINVAL);
     }
 
-    if(avctx->channels != 1){
-        av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
-        return AVERROR(EINVAL);
-    }
+    avctx->channels       = 1;
+    avctx->channel_layout = AV_CH_LAYOUT_MONO;
 
     c->code_size = avctx->bits_per_coded_sample;
     if (c->code_size < 2 || c->code_size > 5) {