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ALE (Avid Log Exchange)

Reading and writing shot logs, and where each column lands on a clip.

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An ALE is a tab-separated shot log: a Heading of key/value pairs, a Column line naming the fields, and a Data section with one row per clip. It is a list of clips rather than a cut, so a file reads as a SerializableCollection of clips, not a timeline.

What becomes what

ALEDocument
Heading pairsthe collection's metadata["ALE"]["header"]
Column orderthe collection's metadata["ALE"]["columns"]
Namethe clip's name (and stays as a column)
Start, Duration, Endthe clip's source_range
Source Filean ExternalReference on the clip
CDL, ASC_SOP, ASC_SATthe clip's metadata["cdl"]
every other columnthe clip's metadata["ALE"]

Keeping the unrecognized columns and the column order is what makes a round trip lossless: upstream's own sample.ale reads and writes back byte for byte.

Rates

Unlike an EDL, an ALE states its rate, in the heading's FPS, and that rate wins over the one you pass, because the file was written for it. Timecode exists only at SMPTE rates, so a heading saying 23.976 is read at 24000/1001; the heading keeps the spelling it arrived with. A rate that is not near a SMPTE rate is refused rather than quietly rounded.

Quirks kept from upstream

  • A value containing a tab is written as-is and becomes two columns when read back. Upstream means to replace tabs with spaces and throws the result away.
  • The Name column stays in metadata["ALE"] as well as becoming the clip's name, so it is in the document twice. The writer depends on this: it discovers columns from that metadata.

Where it differs from upstream

  • A doubled sign such as --1.0 in an ASC_SOP column simply does not start a number. Upstream matches it and then fails to convert, failing the whole row.
  • Reading moves ASC_SOP, ASC_SAT and CDL into metadata["cdl"], and the writer rebuilds those columns from there. Upstream's writer looks only at the ALE metadata, so a graded file it has just read writes those columns blank. The numbers go back out through a float, so -0.0870 is written as -0.087.
  • The writer snaps the heading's rate to a SMPTE rate the same way the reader does. Upstream writes at the stated decimal, so a file at 23.976 comes back with every time slid by a couple of frames.

The crate's README has the Rust options.