Html5 video start loading slowly on android

i am using html5 video tag for small videos ( max 30 sec) in my app , and ffmpeg to encode it to mp4 using the faststart flag. The problem is on iphone it starts instantly, but on android it takes between 5 to 15 seconds to start. I even tried to encode it to webm for android but it didnt make any diffrence.
Why does it take so much time on android and how can i fix it?