Add a audio preview API

[cfillion]

Exposes REAPER's source preview API with additional features:

• Full play rate / pitch support
• Fade in/out (simple linear)
• Apply volume when previewing through a track
• Panning

Adds these features compared to the existing preview functions in js_ReaScript API:

• Play through a project track
• Change any parameter on the fly while preview is active (except source and length)
• Query playback status (eg. position, peaks)
• Measure align

Adds CF_PCM_Source_SetSectionInfo for previewing in reverse or limit the length (without requiring a MediaTake, unlike BR_SetMediaSourceProperties).

local source = reaper.PCM_Source_CreateFromFile(file)
if not source then return end

if reverse then
  local section = reaper.PCM_Source_CreateFromType('SECTION')
  reaper.CF_PCM_Source_SetSectionInfo(section, source, 0, 0, true)
  reaper.PCM_Source_Destroy(source)
  source = section
end

if preview then reaper.CF_Preview_Destroy(preview) end

preview = reaper.CF_CreatePreview(source)
if outToTrack then
  reaper.CF_Preview_SetOutputTrack(preview, outputProj, outputTrack)
else
  reaper.CF_Preview_SetValue(preview, 'I_OUTCHAN', outputChan)
end
reaper.CF_Preview_SetValue(preview, 'D_POSITION',     position)
reaper.CF_Preview_SetValue(preview, 'B_LOOP',         loop and 1 or 0)
reaper.CF_Preview_SetValue(preview, 'D_VOLUME',       volume)
reaper.CF_Preview_SetValue(preview, 'D_PAN',          pan)
reaper.CF_Preview_SetValue(preview, 'D_MEASUREALIGN', measureAlign)
reaper.CF_Preview_SetValue(preview, 'D_PLAYRATE',     playRate)
reaper.CF_Preview_SetValue(preview, 'D_PITCH',        pitch)
reaper.CF_Preview_SetValue(preview, 'B_PPITCH',       preservePitch and 1 or 0)
reaper.CF_Preview_SetValue(preview, 'I_PITCHMODE',    pitchMode)
reaper.CF_Preview_SetValue(preview, 'D_FADEINLEN',    fadeInLen)
reaper.CF_Preview_SetValue(preview, 'D_FADEOUTLEN',   fadeOutLen)
local length = reaper.CF_Preview_GetValue(preview, 'D_LENGTH')
reaper.CF_Preview_Play(preview)
reaper.PCM_Source_Destroy(source)

Test/demo script at https://gist.github.com/cfillion/7718bd7d3566a94c308ca7a5fdee8105.

[AppVeyorBot]

✅ Build sws 867-master completed (commit 30f96fefc7 by @cfillion)

Windows 64-bit

• build/BuildUtils/SWS_Template.ReaperLangPack
• build/BuildUtils/whatsnew.html
• build/reaper_sws-x64.pdb
• build/sws-2.13.1.0-Windows-x64-preview-api-30f96fef.exe

Windows 32-bit

• build/BuildUtils/SWS_Template.ReaperLangPack
• build/BuildUtils/whatsnew.html
• build/reaper_sws-x86.pdb
• build/sws-2.13.1.0-Windows-x86-preview-api-30f96fef.exe

macOS x86 64-bit

• build/sws-2.13.1.0-Darwin-x86_64-preview-api-30f96fef.dmg

macOS x86 32-bit

• build/sws-2.13.1.0-Darwin-i386-preview-api-30f96fef.dmg

macOS ARM 64-bit

• build/sws-2.13.1.0-Darwin-arm64-preview-api-30f96fef.dmg

Linux x86 64-bit

• build/sws-2.13.1.0-Linux-x86_64-preview-api-30f96fef.tar.xz

Linux x86 32-bit

• build/sws-2.13.1.0-Linux-i686-preview-api-30f96fef.tar.xz

Linux ARM 64-bit

• build/sws-2.13.1.0-Linux-aarch64-preview-api-30f96fef.tar.xz

Linux ARM 32-bit

• build/sws-2.13.1.0-Linux-armv7l-preview-api-30f96fef.tar.xz