static void free_variant_list(HLSContext *c)
{
    int i;
    for (i = 0; i < c->n_variants; i++) {
        struct variant *var = c->variants[i];
        av_freep(&var->playlists);
        av_free(var);
    }
    av_freep(&c->variants);
    c->n_variants = 0;
}