Specific Details on "Video Quality" Compression (SL3)

In order to ascertain some optimal encoding standards, I'm looking for some real numbers on what specifically the video quality slider does in terms of bitrate reduction, profiling, and audio.

For example, if my source file (normally destined let's say, for YouTube) is:

  • H.264 MP4
  • 1920x1080
  • Profile High, Level 4.2
  • Bitrate Encoding CBR 40mbps

What does the Storyline compression scheme actually do?

Does it convert to the encoding standard to VBR? If so, 1-Pass or 2-Pass? What is the target bitrate and max bitrate at each "quality" level (1-9)? What other audio/video characteristics are being altered when Storyline compresses the video?

The file size is clearly being reduced, but I would like to know more about what specifically is being done to the file at the compression level, so that I can find a standard that works best for the media across the many platforms the content may find itself on.

4 Replies
Katie Riggio

Greetings, Joseph!

It looks like you've done some excellent troubleshooting, and I appreciate you bringing your findings to our attention. 

I found the support case where you're already working with one of our Support Engineers, Lea. She'll be in touch after carefully analyzing this information, and I'll follow the conversation!

Joseph Ferraro

Thanks for the follow-up Katie! I'm looking forward to the results of any research on this topic.

Just by a little reverse engineering I can see that SL video quality compression:

A) Significantly reduces the bitrate, even at high values (a "7" reduced it by almost 600%).

B) Sums the video's audio to mono, which is really good information to know ahead of time if there are any risks of phase cancellation involved with the sum (e.g., wide stereo field).

Joseph Ferraro

For anyone curious about the outcome on this one: It was determined that this information is not appropriate for public disclosure / proprietary, however there's a chance we may see some of the higher-level findings in a future knowledge base article. I'll link to it in here should something come out.