What I am doing wrong with this bash variable?

How can I insert a variable into a command? In the case below, I need to concatenate the command with the variable file name.

#!/bin/bash

# Define a timestamp function
timestamp() {
  date +"%D-%T" | tr :/ -
}

# Define the file name
value=$(timestamp)
filename= "/home/pi/media/$value.h264"

#Recording
raspivid -w 800 -h 600 -t 15000 -o $filename -n -rot 270

#Terminate the script
exit