3G2 is a 3GPP2 multimedia container found in older CDMA phone and messaging workflows. The upload pipeline verifies its brand and requires a decodable audio track before making a transcript.
Where this workflow fits
- Legacy phone clips
- CDMA message archives
- Mobile field recordings
Brand evidence identifies the container
3G2 belongs to the ISO base media family, whose members can report overlapping demuxer names. The ingest boundary therefore combines the major_brand value with actual audio and video streams rather than guessing from a generic MP4 token.
Review a legacy mobile capture
Mobile clips often place a close voice beside handling noise and abrupt cuts. Check words around every cut, plus dates and contact names that a narrowband recording can make difficult to distinguish.
Before you upload
- Play the original phone file and confirm that the voice track continues past scene changes.
- Preserve the unmodified source because another export can add a second generation of compression.
Limits worth knowing
- Older phone captures may use narrow speech bandwidth, tiny frame sizes, or variable timestamps.
- A renamed MP4 is rejected when its ISO major brand contradicts the declared 3G2 extension.
Questions from the workflow
How is 3G2 distinguished from MP4?
The worker reads the ISO media major brand and stream list. A shared MP4-family demuxer name alone is not enough to label a file as 3G2.
Reviewed sources
- IANA Media Types registry · checked 2026-07-20
- RFC 4393: 3GPP2 media types · checked 2026-07-20