FFmpeg wrapper

namespace GeOda.PicturesEh

type SnapConfig =
    {
        programmeId: string
        carrierId: string
        outputSnapPath: string
        outputSnapName: string
        outputSnapTime: string
    }

module PicturesEh =
    open System.Diagnostics
    open System
    open System.IO

    let GenerateSearchPaths (programmeId: string, carrierId: string) =
        [@"\\somePath\6\"; @"\\somePath\5\"; @"\\somePath\4\"; @"\\somePath\3\"; @"\\somePath\2\";]
        |> List.map(fun path -> System.String.Format("{0}{1}{2}{3}{4}", path
                                                            , programmeId.Substring(0, 6) + "\\"
                                                            , programmeId.Substring(6, 2) + "\\"
                                                            , programmeId.Substring(0, 12) + "\\"
                                                            , carrierId + "_ID180.mp4"))

    let FindFilePath searchPaths =
        searchPaths
        |> List.find(fun searchPath -> System.IO.File.Exists(searchPath))

    let GenerateFFmpegParameters time outputPath filePath =
        System.String.Format("{0}{1}{2}{3}{4}", @"-y -ss ", time, " -i ", 
                                filePath, @" -s 96x54 -f image2 -vframes 1 " 
                                + outputPath)

    let RunCommand parameters =
        let processInfo = new ProcessStartInfo(@"C:\test\ffmpeg\bin\ffmpeg.exe", parameters)
        processInfo.UseShellExecute <- false
        processInfo.CreateNoWindow <- true
        processInfo.RedirectStandardOutput <- true
        processInfo.RedirectStandardError <- true
        try 
            let proc = System.Diagnostics.Process.Start(processInfo)
            let output = proc.StandardError.ReadToEnd() //writes to standard error not output, why?
            proc.WaitForExit()
            output
        with 
            | :? Exception as ex -> 
                ""

    let TakeSnap snapConfig =
        GenerateSearchPaths (snapConfig.programmeId, snapConfig.carrierId)
        |> FindFilePath
        |> GenerateFFmpegParameters snapConfig.outputSnapTime (snapConfig.outputSnapPath + snapConfig.outputSnapName) 
        |> RunCommand
        |> printfn "output: %s" 
        
        snapConfig.outputSnapPath + snapConfig.outputSnapName