Is it possible to gather the same results by sending regular data, as in not testing data?
I don't believe so, at least not using iperf. If you can capture the real data with pcap/tcpdump/wireshark, then you should be able to use wireshark to determine the jitter.
I suspect iperf calculates jitter using a formula like is defined in RFC 3550 for the RTP protocol. You would probably need to dig into the source to know for certain.
If Si is the RTP timestamp from packet i, and Ri is the time of
arrival in RTP timestamp units for packet i, then for two packets
i and j, D may be expressed as
D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si)
The interarrival jitter SHOULD be calculated continuously as each
data packet i is received from source SSRC_n, using this
difference D for that packet and the previous packet i-1 in order
of arrival (not necessarily in sequence), according to the formula
J(i) = J(i-1) + (|D(i-1,i)| - J(i-1))/16
Whenever a reception report is issued, the current value of J is
The jitter calculation MUST conform to the formula specified here
in order to allow profile-independent monitors to make valid
interpretations of reports coming from different implementations.