if (!avformat_open_input(&ast->sub_ctx, "", sub_demuxer, NULL)) {
ff_read_packet(ast->sub_ctx, &ast->sub_pkt);
*st->codec = *ast->sub_ctx->streams[0]->codec;
if (!avformat_open_input(&ast->sub_ctx, "", sub_demuxer, NULL)) {
ff_read_packet(ast->sub_ctx, &ast->sub_pkt);
*st->codec = *ast->sub_ctx->streams[0]->codec;