How to decrease the data length each time

[ori0930]

Dear all,
I use RTP/MPEG Transport Stream and Video - H.264+MP3(MP4) to stream video.
Also, I use Wireshark to check my data, and find each time the frame is 1370 bytes(data is 1328 bytes).
Now I want to decrease the data length(ex:1328->800), but I can't find how to decrease the data length.
Is there any method to decrease the data length?

Thanks your help!
Best regards!