Can one learn meditation on their own? Can I learn Vipassana meditation or other Buddhist meditation techniques like Shamatha on my own using books and online videos? 
This is because it is sometimes hard to find good genuine teachers. 
Or do I definitely need to seek a teacher?
According to my understanding you can learn and start meditation (Samatha or Vipassana) using books and online videos. Of course there are some meditation practices which will be better to learn with a real teacher. Apart form that specially when you have any practical questions or troubles with the meditation or the practice, it is really helpful to get some advice from an experienced teacher. 

Further, when you learn by yourself make sure to refer some credible resource (books or online videos) as there are a lot of verities available nowadays. Hope this helps.