使用PowerShell和ffmpeg编写一个自动压缩视频脚本

param(
    [Parameter(Mandatory=$true)]
    [string]$InputFile,

    [Parameter(Mandatory=$true)]
    [string]$OutputFile,

    [Parameter(Mandatory=$false)]
    [switch]$Lossless,   # 是否启用无损压缩

    [Parameter(Mandatory=$false)]
    [int]$CRF,           # 用户可手动指定 CRF 值

    [Parameter(Mandatory=$false)]
    [int]$TargetSizeMB   # 目标大小 (MB)
)

# 检查 ffmpeg 是否可用
if (-not (Get-Command ffmpeg -ErrorAction SilentlyContinue)) {
    Write-Host "错误: 未检测到 ffmpeg，请先安装并配置到 PATH。" -ForegroundColor Red
    exit 1
}

# 获取视频信息
$info = & ffprobe -v error -select_streams v:0 -show_entries stream=width,height,r_frame_rate,bit_rate,duration -of default=noprint_wrappers=1 "$InputFile"

$width   = ($info | Select-String "width="   | ForEach-Object { $_.ToString().Split("=")[1] })
$height  = ($info | Select-String "height="  | ForEach-Object { $_.ToString().Split("=")[1] })
$fpsRaw  = ($info | Select-String "r_frame_rate=" | ForEach-Object { $_.ToString().Split("=")[1] })
$bitrate = ($info | Select-String "bit_rate=" | ForEach-Object { $_.ToString().Split("=")[1] })
$duration = ($info | Select-String "duration=" | ForEach-Object { $_.ToString().Split("=")[1] })

# 计算帧率
$fpsParts = $fpsRaw -split "/"
if ($fpsParts.Count -eq 2) {
    $fps = [math]::Round([double]$fpsParts[0] / [double]$fpsParts[1], 2)
} else {
    $fps = [double]$fpsRaw
}

Write-Host "检测到视频: ${width}x${height}, ${fps}fps, 码率=${bitrate}bps, 时长=${duration}s"

# 判断压缩模式
if ($Lossless) {
    # 无损压缩
    $codec = "libx264"
    $preset = "slow"
    $extraParams = "-crf 0"
    $audioCodec = "copy"
    Write-Host "选择无损压缩: $codec $preset $extraParams, 音频=$audioCodec"
} elseif ($TargetSizeMB) {
    # 目标大小模式
    $targetBitrate = [math]::Round(($TargetSizeMB * 8 * 1024) / [double]$duration)
    Write-Host "目标大小模式: 目标=$TargetSizeMB MB, 计算码率=$targetBitrate kbps"

    $codec = "libx264"
    $preset = "slow"
    $extraParams = "-b:v ${targetBitrate}k"
    $audioCodec = "aac -b:a 128k"
    Write-Host "选择目标大小压缩: $codec $preset $extraParams, 音频=$audioCodec"
} else {
    # 有损压缩，自动推荐 CRF
    if ($CRF) {
        $chosenCRF = $CRF
        Write-Host "用户指定 CRF=$chosenCRF"
    } else {
        if ([int]$width -ge 1920 -or [int]$bitrate -ge 4000000) {
            $chosenCRF = 23
        } elseif ([int]$width -ge 1280 -or [int]$bitrate -ge 2000000) {
            $chosenCRF = 26
        } else {
            $chosenCRF = 28
        }
        Write-Host "自动推荐 CRF=$chosenCRF"
    }

    $codec = "libx264"
    $preset = "slow"
    $extraParams = "-crf $chosenCRF"
    $audioCodec = "aac -b:a 128k"
    Write-Host "选择有损压缩: $codec $preset $extraParams, 音频=$audioCodec"
}

# 执行压缩
$ffmpegCmd = "ffmpeg -i `"$InputFile`" -c:v $codec -preset $preset $extraParams -c:a $audioCodec `"$OutputFile`""
Write-Host "执行命令: $ffmpegCmd"
& cmd /c $ffmpegCmd

# 显示文件大小对比
$origSize = (Get-Item $InputFile).Length
$newSize  = (Get-Item $OutputFile).Length

Write-Host "原始大小: $([math]::Round($origSize/1MB,2)) MB"
Write-Host "压缩后大小: $([math]::Round($newSize/1MB,2)) MB" -ForegroundColor Green

./auto_compress.ps1 -InputFile "input.mp4" -OutputFile "output.mp4"

./auto_compress.ps1 -InputFile "input.mp4" -OutputFile "output.mp4" -CRF 24

./auto_compress.ps1 -InputFile "input.mp4" -OutputFile "output.mp4" -Lossless

./auto_compress.ps1 -InputFile "input.mp4" -OutputFile "output.mp4" -TargetSizeMB 100