Fix the bash so Letvcloud can use it

Sina video is dead.

However Letvcloud can use the same trick.

I've made a few changes:

1. Change the default bitrate to 1990K. For "direct upload" of Bilibili and Acfun, this would avoid further transcode.

2. Change the output format to MP4. FLV is causing transcoding failure with Letvcloud.

Haven't tried 3xspeed with Letvcloud though.