Blogger Video Frame 100% shown on mobile, and not cut off:

• First of all go to your blogger dash board.
• Then click on Appearance from left side bar.
• Click on Editor Option and go to Css.
• Copy the Code given Below and Paste it below on style sheet.

.video-container {
 position: relative;
 padding-bottom: 56.25%;
 padding-top: 30px;
 height: 0;
 overflow: hidden;
}
.video-container iframe, 
.video-container object, 
.video-container embed {
 position: absolute;
 top: 0;
 left: 0;
 width: 100%;
 height: 100%;
}
.entry-content img, 
.entry-content iframe, 
.entry-content object, 
.entry-content embed {
 max-width: 100%;
}

<div class="video-container"> Video Embed code </div>

<div class="video-container"><iframe frameborder="0" width="620" height="470" src="//www.dailymotion.com/embed/video/xxxxx" allowfullscreen></iframe></div>

<div class="video-container"><iframe src="https://www.facebook.com/video/embed?video_id= 0000000000" width="620" height="400" frameborder="5"></iframe></iframe></div>