How to extract all audio channels from a master video and burn it to proxy H.264 using FFMPEG transcoder?

Videos with multiple audio channels (multi audio tracks) are common in the media industry. The default FFMPEG parameters should be slightly altered in order to deal with these videos.
 
Please use the below parameter to extract all audio channels from a master video and burn it to proxy file. 
 
Video Settings:  -i "eSourceFile" -y -s 1920x1080 -map 0:v -map 0:a -b:v 1024k -vcodec libx264 -r eSourceFrameRate -movflags faststart -pix_fmt yuv420p "eVideoProxy" 

Not all browsers support playing of multi-audio tracks embedded to the same proxy files. As of now, it was only supported by IE 11 browser but now Chrome browser has added a feature to its settings-experimental flags section to support playing of multiple audio tracks. Refer below article to enable it at Chrome setting level:
http://emamonline.smartertrack.com/kb/a365/does-emam-support-playing-multiple-embedded-audio-tracks.aspx
 
If you want to extract specific audio channels from a video, you can refer this KB article - http://support.empressmam.com/kb/a153/extract-specific-video-and-audio-tracks-using-ffmpeg.aspx