fprintf(stderr, "[%s @ %p]", avctx->codec->name, avctx);
fprintf(stderr, "[%s @ %p]", avctx->codec ? avctx->codec->name : "?", avctx);
static void av_log_default_callback(AVCodecContext* avctx, int level, const char* fmt, va_list vl){    static int print_prefix=1;    if(level>av_log_level)	    return;    if(avctx && print_prefix)        fprintf(stderr, "[%s @ %p]", avctx->codec->name, avctx);            print_prefix= (int)strstr(fmt, "\n");            vfprintf(stderr, fmt, vl);}