riff: fix parsing ffmpeg wave stdout output

[sscobici]

Adding back 4 bytes for parent length comparison with u32:MAX as it was reduced by 4 bytes in commit f72ac41

This fixes symphonia-check some.mp3 which currently returns error:

Test interrupted by error: malformed stream: riff: chunk length exceeds parent (list) chunk length

[pdeljanov]

Hmm, I see the issue, and this would be a workaround, but I don't think it is a correct fix. Subtracting 4 was just one possible case for AIFF and WAVE, however, it may be different for other RIFF-based formats like AVI which would also be implemented in this crate.

I got hit with a similar issue with MkvReader. I'm rewriting it now so that EbmlIterator will take the the length as an option since these magic values always seem to cause bugs in the end.

So, I think the ideal fix here too would be to make the length passed to the chunk reader an Option<u64>. In the case where the length is unknown, we'd just pass None.

[sscobici]

Cancelling this workaround PR. Will wait for your refactoring.

[pdeljanov]

I fixed this issue in 5a9bc17 by passing an Option<u32> to the ChunkReader and detecting when FFmpeg sets it to 0xffff'ffff.

Please help test both AIFF and WAVE with this new change.

[sscobici]

I don't have too many files but ffmpeg output comparison now works with this commit, while previously it was failing. Thanks