javascript下载文件

代码片段如下

/**
 * 创建并下载文件
 * @param  {String} fileName 文件名
 * @param  {String} content  文件内容
 */
function createAndDownloadFile(fileName, content) {
    var aTag = document.createElement('a');
    var blob = new Blob([content]);
    aTag.download = fileName;
    aTag.href = URL.createObjectURL(blob);
    aTag.click();
    URL.revokeObjectURL(blob);
}

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利用mp4fragment 转换mp4格式

最近做一个项目，利用到Media Source Extensions 需要将普通的mp4文件转换问fragment格式的mp4文件，从https://www.bento4.com/downloads/ 下载对应的的二进制文件，对应的bin目录文件下有mp4fragment 可执行程序。教研的视频文件有120来个，打算使用shell脚本来执行这些程序

对应shell记录如下

#!/bin/sh

cd "/Users/vipkid/Downloads"
rm -rf  fragmentDir
rm -rf  cutMp4
## 创建 fragementDir
mkdir fragmentDir 
## 创建 mp4
mkdir cutMp4


path="/Users/vipkid/Downloads/final_trail_videos_1215"

files=$(ls $path)
# 裁剪mp4
for FILE in $files
    do
    ./ffmpeg -i  $path"/"$FILE -filter:v "crop=720:540:560:200" -c:a copy "/Users/vipkid/Downloads/cutMp4/"$FILE
    echo $FILE
    done
# 转换格式
for FILE in $files
   do
    cd "/Users/vipkid/Downloads/Bento4-SDK-1-6-0-637.universal-apple-macosx/bin/"
     ./mp4fragment  --verbosity 3  "/Users/vipkid/Downloads/cutMp4/"$FILE  "/Users/vipkid/Downloads/fragmentDir/"$FILE 
    echo $FILE
   done
#!/bin/sh

## 裁剪文件 将文件裁剪成 320 240的 然后转换为fragment mp4
cd "/Users/vipkid/Downloads"
## 创建 fragementDir
mkdir cut320
mkdir fragmentDir320


path="/Users/vipkid/Downloads/cutMp4"

files=$(ls $path)
# 裁剪mp4
for FILE in $files
    do
    ./ffmpeg -i  $path"/"$FILE -vf scale=320:240 -acodec aac -vcodec h264 "/Users/vipkid/Downloads/cut320/"$FILE
    echo $FILE
    done
# 转换格式
for FILE in $files
   do
    cd "/Users/vipkid/Downloads/Bento4-SDK-1-6-0-637.universal-apple-macosx/bin/"
     ./mp4fragment  --verbosity 3  "/Users/vipkid/Downloads/cut320/"$FILE  "/Users/vipkid/Downloads/fragmentDir320/"$FILE 
    echo $FILE
   done
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