slices(from:duration:stride:)

Declaration

func slices(from start: TimeInterval, duration: TimeInterval, stride: TimeInterval? = nil) throws -> SHSignature.Slices

Parameters

• start:

  The starting value to use for the sequence.

• duration:

  The desired duration of each sliced signature.

• stride:

  The amount to step by for each slice. Must be a non-zero positive value.

Return Value

A sequence from start of duration length. Each value in the sequence is separated by stride.

Discussion

When you recognize audio with match(_:), signature duration should be between minimumQuerySignatureDuration and maximumQuerySignatureDuration. Use this method to slice signatures longer than the maximum duration.

Slicing allows you to test specific parts of the audio. If you know certain parts of an audio are clearer or more likely to have recognizable content, prioritize matching those slices.

The code below creates slices from a signature and uses the first three slices to find a match:

let signature = try await SHSignatureGenerator.signature(from: audioAsset)
let slices = try signature.slices(from: 2.0, duration: 10.0, stride: 5.0)

// Use the first 3 slices to find a match.
for try await slice in slices.prefix(3) {
   session.match(slice)
}

You can use AsyncSequence operators like prefix(_:) or first(where:) to choose which slices are processed.

The stride parameter controls overlap between slices. A smaller stride creates more slices with greater overlap, which increases the number of matching requests. Larger strides create fewer slices, however there are fewer matching requests.

For continuous matching as audio becomes available, use matchStreamingBuffer(_:at:), which automatically generates and matches signatures from audio buffers.

See Also

Slicing signature segments

• SHSignature.Slices