Congratulations to a good photo.
Positive strikes are usually stronger than negative and they are not so disposed to re-ignite trough the same channel as the negative ones, as the discharge usually is completed trought the first ignition. With 30 rames per second, it might be hard to see the difference anyway.
Regardig the sound, your experience of the thunder depends on what angle the lightening channel had compared to your standing point. If all or most parts of the channel had the same distance to you, you may hear a thunder that is more like a rifle shot.
If the lightenng channel "was pointing inyour direction", and perhaps 1 kilometer long, you will hear a longer rolling sound.
Furthermore the type of rifle shot thunder will be percepted as so deafening that you will hardly notice the weaker echoes that may be caused by landscape details or clouds, where the longer rolling thunder with no big crecendo will appear even longer because of echoes.
Why does the far away thunder make things rattle more than the nearby?
I coud imagine that the shock wave of a nearby lightening emits in circles and so a certain part f a shock vave only hits a part of a wall, while the next part of the wall is hit milliseconds later.
With thunder far away, the radius of the shock wave is so large that the perimeter is almost a straight line, and the wall of your house will be hit in its whole lenght in what appears to be simultaneously. At least that is my theory.
Some years ago we had a heavy lightening storm here. I heard a very loud "explosion" and then silence, but could soon smell the ozon like smell. I realized that it was a close strike, and went around the house to see if everything was OK. Immediately I found nothing to be wrong, but I wondered why my neighbour across the road did not notice that their dinner was being overcooked, as smoke came out of the kitchen vent.
But their house had been hit, and caught fire, the result below is seen in the picture which I took from my roof.
Nobody got injured, not even their canary.
Police investigation stated that the metal tube of the kitchen vent had a direct strike of lightening.