html5 video format 转换

不错的文章，转载一下，

http://paulrouget.com/e/converttohtml5video/

Here are my 3 command lines to convert to WebM, OGG/Theora and mp4:

• OGG/Theora

  ffmpeg -i input.mov \  -acodec libvorbis -ac 2 -ab 96k -ar 44100 \  -b 345k -s 640x360 output.ogv

• WebM/vp8

  ffmpeg -i input.mov \  -acodec libvorbis -ac 2 -ab 96k -ar 44100 \  -b 345k -s 640x360 output.webm

• MP4/h264

  ffmpeg -i input.mov \  -acodec libfaac -ab 96k \  -vcodec libx264 -vpre slower -vpre main \  -level 21 -refs 2 -b 345k -bt 345k \  -threads 0 -s 640x360 output.mp4

Video are resized to 640x360 with a bitrate of 345k.