在PHPmotion中使用ffmpeg＆mp4box将视频从任何视频转换为mp4时，如何减小文件大小？

Question

I am using ffmpeg & mp4box in my PHPmotion site to convert videos to mp4 format. When I convert a 50MB video to mp4, the file size remain same. So Its affecting the video streaming in my site. So I want to reduce the file size of the video in conversion. This is my code example, that I've used the site for converting m4v videos in PHPmotion.

$ffmpeg_cmd2_2 = "$config[path_to_ffmpeg] -i $raw_video_path -vcodec libx264 -vpre veryfast -crf 15 -b 5120000 -threads 0 -acodec libfaac -ac 2 -ab 128k -ar 44100 -f mp4 $new_flv_1";
$mp4box_cmd = "$mp4box_path -add $new_flv_1 $new_flv_2" 

When I use this command,it converts the m4v file to mp4 format, but the filesize doesn't change. What command I should use in this to reduce the filesize during video conversion in PHPmotion? Can anyone write a ffmpeg command to reduce the filesize during conversion ?

Answer 1

There are two main factors involve in reducing the size of mp4 video

i: width and height of video, greater their widths, greater will be size and slower will be streaming e,g 360p, 480p, 720p, 1080p

ii: video bitrate, greater will be their bitrate, higher will be quality, size and slower will be their streaming.

For faster streaming i recommend using

i: 480x360 or lower width and height of video ii: -b value 360k or lower. iii: -ab value 64k (optional)

Hope this will help you.

Answer 2

Apart from using smaller video frame size, you need to use higher crf value to achieve bitrate reduction while maintaining good video quality.

Replace this

-crf 15 -b 5120000

with

-crf 22