Having trouble with Infra Red LED

I'm able to record and playback IR codes using Ken Shiffiff's IR library:

However, my Sony DVD player is not responding to the code sent by my IR LED. :frowning:
I can see that the IR LED is blinking using a digital camera.

I've tried these two IR LEDs:
model 276-143:

model 276-142:

Has anyone successfully using this library using these IR LEDs?
Which IR LED I should use instead? Thanks!