* @param fmt_name Format name, or NULL if unknown
* @return Channel layout mask
*/
-int64_t avcodec_guess_channel_layout(int nb_channels, enum CodecID codec_id, const char *fmt_name);
+uint64_t avcodec_guess_channel_layout(int nb_channels, enum CodecID codec_id, const char *fmt_name);
struct AVAudioConvert;
typedef struct AVAudioConvert AVAudioConvert;