[fyi][video] Video clip creation fails on YFCC

[bjuncek]

Culprit:

known bug in H264 decoding

For certain filetypes - specifically some related to YFCC100m dataset - there is an error whilst creating the VideoClips object. Not 100% sure what is the best way of fixing the issue (other than try-catch in read_video_timestamps.

Even if the fix is not critical, we should make sure that is caught in C++ or future versions.

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Sample YFCC video in question:

27b66931edb88a5f7e6c756ea65fd8.mp4
there are at least 50 of them, probably more.

Minimal repro example

video_list = ['~/yfcc100m/mp4/27b/669/27b66931edb88a5f7e6c756ea65fd8.mp4']
VideoClips(video_list, 8, 1)

or even simpler

import av
container = av.open('~/yfcc100m/mp4/27b/669/27b66931edb88a5f7e6c756ea65fd8.mp4')
for idx, frame in enumerate(container.decode({'video': 0})):
    pass

Output error stack:

Invalid NAL unit size (34173 > 22144).
Error splitting the input into NAL units.
stream 1, offset 0x16baf66: partial file
Invalid NAL unit size (24747 > 6180).
Error splitting the input into NAL units.

[fmassa]

Can you see if with the new video reader from @stephenyan1231 this is still an issue?

[bjuncek]

Yup - using 'video-reader' backend solves the issue.
Let me know if we want to close this or keep it open until the new backend is rolled out by default

[fmassa]

Let's keep this open, we can probably fix it on the PyAV-based read_video. I think it might just require adding a proper try: except there. Could you have a look at it and see if we can catch it nicely?

[bjuncek]

S.G.

@fmassa yeah, but probably not before Wednesday :|

[fmassa]

no worries