FFmpeg 5 incorrect extradata parsing

[ChristianFeldmann]

Describe the bug
When parsing bitstreams using the new ffmpeg version, the parameter sets were not opbtained correctly from the extradata because the exptradata is not parsed correctly.

To Reproduce
Steps to reproduce the behavior:

1. Use ffmpeg 5
2. Open an mp4 file. You will not see the parameter sets being parsed.

Expected behavior
The parameter sets should be parsed correctly. Also on FFmpeg 5.

Version (please complete the following information):

• OS: any
• Version any
• FFmpeg 5

[ChristianFeldmann]

Fix was merged. There is no specific test for this yet. We will also need a test suite for the ffmpeg stuff at some point though ...