get_Chunk

get_Chunk

Get Wave Chunks

Wave files are stored in chunks. Gets the chunks within a wave file.

Notes

When this property is first enumerated, it will add additional properties for each trimmed chunk name and their start

• $this.#data will contain the data chunk bytes
• $this.#data.start will contain the data chunk start
• $this.#fmt will contain the format fmt chunk bytes
• $this.#fmt.start will contain the fmt chunk start

Additional chunks are optional.

View Source

<#
.SYNOPSIS
    Get Wave Chunks
.DESCRIPTION
    Wave files are stored in chunks.  Gets the chunks within a wave file.
.NOTES
    When this property is first enumerated,
    it will add additional properties for each trimmed chunk name and their start

    * `$this.#data` will contain the `data` chunk bytes
    * `$this.#data.start` will contain the `data` chunk start
    * `$this.#fmt` will contain the format `fmt ` chunk bytes
    * `$this.#fmt.start` will contain the `fmt ` chunk start

    Additional chunks are optional.
.LINK
    https://en.wikipedia.org/wiki/WAV#WAV_file_header
.LINK
    https://en.wikipedia.org/wiki/Resource_Interchange_File_Format
#>
# If this has chunks, return them
if ($this.'#Chunk') { return $this.'#Chunk'}

# If this is not a stream, we can't read it.
if ($this -isnot [IO.Stream]) { return }

# If this cannot read or seek, we can't read it.
if (-not ($this.CanRead -or $this.CanSeek)) { return }

# Create a binary reader
$binaryReader = [IO.BinaryReader]::new($this)
# seek to zero
$null = $this.Seek(0, 'begin')

# RIFF should be the first four characters
$riff = $binaryReader.ReadChars(4) -join ''

# If that is not the case, it is not a wave
if ($riff -cne 'RIFF') { throw "Not a Wave (no RIFF header)" }

# The next four bytes are the wave file size.
# We do not actually care about this right now, and other properties will reveal it.
$null = $binaryReader.ReadUInt32()

# Followed by the four character File Format ID
$fileFormatId = $binaryReader.ReadChars(4) -join ''

# Which must be `WAVE`
if ($fileFormatId -cne 'WAVE') { throw "Not a Wave (incorrect file format id: $fileFormatID)" }
# While we have no reached the end of the stream
$chunks = @(while ($this.Position -lt $this.Length) {
    # Note the chunk start
    $chunkStart = $this.Position
    $chunk = [Ordered]@{
        start = $chunkStart
        # then get the ID
        id = $binaryReader.ReadChars(4) -join ''
        # and the length
        length = $binaryReader.ReadUInt32()
    }
    
    if (-not $chunk.id) {
        throw "Malformed Chunks (no must have ID)"
    }

    # Initialize an array to hold the length
    $chunk.data = [byte[]]::new($chunk.length)
    # and read the chunk
    $null = $this.Read($chunk.data, 0, $chunk.Length)
    # Then cache the chunk and it's start into note properties.
    $this | Add-Member NoteProperty "#$($chunk.id.Trim())" $chunk.data -Force
    $this | Add-Member NoteProperty "#$($chunk.id.Trim()).start" $chunk.start -Force
    # and emit the chunk.
    $chunk
})

# Reset our position to zero.
$null = $this.Seek('0','Begin')
# cache the chunks
$this | Add-Member NoteProperty '#Chunk' $chunks -Force
# and return the chunks.
return $chunks