Correlation between a signal segment and its stretched replica
Say you got two similar signals when one of them is stretched and you want to know the straching ratio...
Seems like you can 
1. guess the straching ratio
2. resample the short signal with a resampling ratio equal to your guessed straching ratio.
3. Find the max of the convolution between the signals.
4. Optimize the estimation of the straching ratio using a numerical method.