[BUG] Fails to import Canon R5 8K file

[eliot-lightcraft]

Describe the bug I was experimenting with Canon R5 clips, both 4K and 8K, simply opening the file and saving out JPEG frames. The 4K files worked fine with the below Python code but the 8K file didn't.

To Reproduce

Installed OpenImageIO with Homebrew with default settings. 8K file link: https://www.dropbox.com/s/clbr051susjwe0a/8K8A0231.MP4?dl=0

Code:

#!/usr/bin/env python

import OpenImageIO as oiio
from OpenImageIO import ImageBuf, ImageSpec, ImageBufAlgo
import os

src = '8K8A0231.MP4'
buf = ImageBuf(src)

frames = range(buf,nsubimages)
print (frames)

for frame in range(buf.nsubimages):
	buf.reset(src, subimage = frame)
	buf.write('myFrame_{l}.jpg'.format(l=frame))

Expected behavior I executed this from the command line with

python3 pyframes.py

I expected it to write out a numbered series of JPEG still frames like it did with the 4K file. It doesn't seem to open the file correctly.

Platform information:

• OIIO branch/version: today's build from Homebrew
• OS: On Mac OSX 10.15.7, Macbook Pro 2013
• C++ compiler: Xcode
• Any non-default build flags when you build OIIO: none