[FFmpeg-user] Setting up a watch folder to encode adaptive bit rate videos

[Joel Lopez]

Hi,

I've been reading as much stuff as I can find what the best way to
encode key frame aligned videos.  Hopefully you can help me fill in
the blanks.

1.  Single or 2-pass encoding?  I'm reading quality isn't affected
much and that it may be possible to have aligned key frames with
either one.  What do you guys do?

A blog I found says I can just use this:
http://blog.streamroot.io/encode-multi-bitrate-videos-mpeg-dash-mse-based-media-players/

-x264opts 'keyint=24:min-keyint=24:no-scenecut'

Wowza says to do 2-passes like this:
http://www.wowza.com/forums/content.php?213-How-to-use-FFmpeg-with-Wowza-Media-Server-(MPEG-TS)

ffmpeg -y -i bigbuckbunny_1500.mp4 -c:a libfaac -ac 2 -ab 64k -c:v
libx264 -preset:v veryfast -threads 0 -r 24 -g 48 -keyint_min 48
-sc_threshold 0 -x264opts no-mbtree:bframes=1 -pass 1 -b:v 286k -s
384x216 bigbuck-350k.mp4
ffmpeg -y -i bigbuckbunny_1500.mp4 -c:a libfaac -ac 2 -ab 64k -c:v
libx264 -preset:v fast -threads 0 -r 24 -g 48 -keyint_min 48
-sc_threshold 0 -x264opts no-mbtree:bframes=1 -pass 2 -b:v 286k -s
384x216 bigbuck-350k.mp4
ffmpeg -y -i bigbuckbunny_1500.mp4 -c:a libfaac -ac 2 -ab 64k -c:v
libx264 -preset:v fast -threads 0 -r 24 -g 48 -keyint_min 48
-sc_threshold 0 -x264opts no-mbtree:bframes=1 -pass 2 -b:v 836k -s
640x360 bigbuck-900k.mp4


2. I want my videos to work on as many devices as possible of course.
But I'm thinking of starting with 5 or 6 bit rates.  We have only upto
720p sources and stream on a Wowza server.  What bitrates do you
stream?

Apple seems to recommend 8 files
https://developer.apple.com/library/ios/technotes/tn2224/_index.html#//apple_ref/doc/uid/DTS40009745-CH1-SETTINGSFILES

Kaltura says you can get up to 40 if you have different files for
desktop, iOS and Android.
http://knowledge.kaltura.com/best-practices-multi-device-transcoding

Google does 5 versions with live encoder and I'm liking this.  I've
seen they have 144p too on YouTube even though it's not listed.
https://support.google.com/youtube/answer/2853702?hl=en

TLDR;
Single or 2pass for key frame alignment?
How many files and at what bitrates is a good starting point for
mobile and desktop?

Thanks.