detect equal sequences in list

[DPaul]

I love a (simple) challenge. It's possible that I'm missing something,
but the above seems rather complicated to me.
What is wrong with:

film = ["12", "11", "11", "11", "17", "22", "22", "22", "22", "23", "24", "24", "24", "24"]
oldvalue = film[0]
startidx = 0
start_end = []
for idx,value in enumerate (film):
    if value != oldvalue:
        start_end.append([startidx,idx-1])
        startidx = idx
    oldvalue = value      
start_end.append([startidx,idx])        
print(start_end)

Output:
[[0, 0], [1, 3], [4, 4], [5, 8], [9, 9], [10, 13]]

Paul