`ItemLocationBox` (`iloc`) `base_offset` field is incorrect
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Assessment
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Newbie friendliness
- 45/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- javascript, typescript
- Domain
- audio-video-rtc
Research direction
Search the mp4box.js sources for the ItemLocationBox (iloc) parser, most likely under src/parsing or src/box, and read how base_offset is read together with offset_size and base_offset_size per ISO 14496-12 §8.11.3. Reproduce with the linked clusterfuzz AVIF sample and inspect the 8 bytes at offset 118 (FFFF FFFF FFFF 000B), which should yield 18446744073709486091. Done means the parsed base_offset matches that value for this sample.
Written by the indexing model from the issue text.
Description
When loading clusterfuzz-testcase-minimized-avif-4914209301856256.avif.zip), the base_offset is reported as 18446744073709486000, but the 8 bytes starting at offset 118 are FFFF FFFF FFFF 000B which is 18446744073709486091 in base 10.
See ISOBMFF (ISO 14496-12:2020) § 8.11.3 for the details of the iloc box.
- Dominant language
- TypeScript
- Stars
- 2.5k
- Forks
- 390
- Avg merge
- 1d 17h
- Merged PRs (30d)
- 8
Getting set up
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