What does the BWF bext TimeReference field actually store, and what does FFmpeg's WAV code do with it when I copy, re-encode or resample a recorder file?
A BWF bext TimeReference is a 64-bit count of samples since midnight at the file's own sample rate, with no frame-rate field; FFmpeg's WAV demuxer (4bef4614) reports that raw count as time_reference metadata without converting it and does not parse iXML, so tools must divide by the file sample rate (and know the project rate) to get timecode.
A BWF bext TimeReference is a 64-bit count of samples since midnight at the file's own sample rate, with no frame-rate field; FFmpeg's WAV demuxer (4bef4614) reports that raw count as time_reference metadata without converting it and does not parse iXML, so tools must divide by the file sample rate (and know the project rate) to get timecode.
Curator qualifications: Specifications and code read 2026-10-22; no files written or decoded. FFmpeg muxer write_bext default from producer reading.
Limitations: Specifications and code read 2026-10-22; no files written or decoded.
Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.
Structured fields
{
"citations": [
{
"url": "https://tech.ebu.ch/docs/tech/tech3285.pdf",
"note": "EBU Tech 3285 PDF bext struct (pdftotext L396-L403) and field table; FFmpeg 4bef4614 libavformat/wavdec.c L276-L288"
},
{
"url": "http://www.gallery.co.uk/ixml/object_Details.html",
"note": "EBU Tech 3285 PDF bext struct (pdftotext L396-L403) and field table; FFmpeg 4bef4614 libavformat/wavdec.c L276-L288"
},
{
"url": "https://github.com/FFmpeg/FFmpeg/tree/4bef4614fe8e7429600cc445f0e5aad5ec89ba6e/libavformat",
"note": "EBU Tech 3285 PDF bext struct (pdftotext L396-L403) and field table; FFmpeg 4bef4614 libavformat/wavdec.c L276-L288"
}
]
}Evidence claims
- [sourced_fact] A BWF bext TimeReference is a 64-bit count of samples since midnight at the file's own sample rate, with no frame-rate field; FFmpeg's WAV demuxer (4bef4614) reports that raw count as time_reference metadata without converting it and does not parse iXML, so tools must divide by the file sample rate (and know the project rate) to get timecode. · locator: EBU Tech 3285 PDF bext struct (pdftotext L396-L403) and field table; FFmpeg 4bef4614 libavformat/wavdec.c L276-L288 source
Rights
| component | license | hosting | redistribution | modification | training | Evidence and notes |
|---|---|---|---|---|---|---|
| documentation | unknown | permitted | permitted | unknown | unknown | Applies to this original summary only, not to the cited sources. |