打开音频设备段错误是怎么回事？
void open(){
int ret = 0;
char errors[1024] = {0};
//context
AVFormatContext *fmt_ctx =NULL ;

//paket
int count = 0;
AVPacket pkt;

//create file
char *out = "./audio.pcm";
FILE *outfile = fopen(out,"wb+");

char *devicename =  "hw:0,0";
//register audio device
avdevice_register_all();

//get format
AVInputFormat *iformat = av_find_input_format("alsa");

//open audio
if( (ret = avformat_open_input(&fmt_ctx, devicename, iformat, NULL)) < 0)
{
    av_strerror(ret, errors, 1024);
    printf("Failed to open audio device, [%d]%s\n", ret, errors);
    return;
};

av_init_packet(&pkt);
//read data form audio
while(ret = (av_read_frame(fmt_ctx, &pkt))== 0&& 
    count++ < 500) {
    av_log(NULL, AV_LOG_INFO, "pkt size is %d（%p）, count=%d\n", pkt.size,pkt.data, count);
    fwrite(pkt.data, 1, pkt.size, outfile);
    fflush(outfile);
    av_packet_unref(&pkt);//release pkt
}

fclose(outfile);
avformat_close_input(&fmt_ctx);//releas ctx
return;

}

int main(){

open();

return 0;

}