static inline void writer_print_rational(WriterContext *wctx,
                                         const char *key, AVRational q, char sep)
{
    AVBPrint buf;
    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_AUTOMATIC);
    av_bprintf(&buf, "%d%c%d", q.num, sep, q.den);
    writer_print_string(wctx, key, buf.str, 0);
}
static inline void writer_print_rational(WriterContext *wctx,
                                         const char *key, AVRational q, char sep)
{
    AVBPrint buf;
    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_AUTOMATIC);
    av_bprintf(&buf, "%d%c%d", q.num, sep, q.den);
    writer_print_string(wctx, key, buf.str, 0);
}