Image and audio compression setting when publishing from SL3

May 18, 2017

I've pre-optimized my images and mp3 files before inserting them into my project. I've used .png files mainly for their transparency feature and I've compressed a few of my mp3 files down to 8 kbps because they are used as very low volume background sounds.

I've noticed that at the default "Standard" quality setting for publishing, SL3 is INCREASING the size of my png files significantly (from 448KB to 796KB) and my one mp3 file went from 198KB up to over 1MB in size. I don't want blanket compression sizes for all of my media, so is there a way to tell SL to not recompress or re-encode any of my files?

9 Replies
Ashley Terwilliger-Pollard

Hi Michael,

Certain MP4 videos can be set to no compress them at all - as you'll see noted here. (More details here too)

As for the images and other elements, those will be compressed and Storyline is working to make the smallest possible file without a loss of quality for playback. Since you're seeing some odd behavior with the images and sizes after the fact could you share some of those examples with us? 

Michael Anderson

I've attached a small demo project containing one of my images and one of my mp3 files. The original png file was 440KB but has grown to 778KB in the published output, using the Standard setting. The mp3 file has grown from 198KB to 1.1MB.

This is not good if I've already optimized the size and quality of my files depending upon their use in the project. Having a blanket compression level for all of my images or mp3s doesn't really work for this reason. I've compressed my 198KB mp3 down to 8kbps because it's about 3 minutes long, and is only heard as very low volume background music, but other mp3s in my project are left at 96kbps. I think this is pretty important, especially when trying to optimize project playback for mobile users.

Is there any way to tell SL NOT to re-compress my files? The only work-around I can think of is to MANUALLY replace all of my assets within the published output, but if I have to resort to that I'll probably be making some little voodoo dolls soon afterwards... :)

Michael Anderson

I did a little test and manually copied my originally compressed media over their corresponding files in the Storyline published output folder. I have only about 20 files so far as I'm about 25% into my project. The re-compressed Storyline published output folder totals about 12MB whereas my published output should have been around 9MB if the files had not been re-compressed. That's about a 30% increase in size.

Ashley Terwilliger-Pollard

Hi Michael,

Thanks for sharing the .story file here with us - I published it and didn't change any of the settings below:

Here is what I saw:

  • Original project file size was 5.1 mb, published zipped folder was 2.91 mb
  • When extracting the .story file I was able to see the original file size of the audio (on left in image) and then the file size upon publish (on right). You'll see that the file size is increased upon inserting into Storyline but it doesn't increase once published and is smaller:

I also wanted to know if you were using the checkbox to "optimize audio volume". One other thought that could explain a difference, if the audio bitrate of the original audio was lower than what was set on publish the audio file size would increase.

Let me know if you can take a look at those settings and if you have any other questions! 


Michael Anderson

The original file size of that mp3 is 198KB, before being inserted into Storyline. Yes, it was encoded at 8kbps, which Storyline may not be able to do. If the published output file is over 1MB, then that is still 5x the original file size. Please look at the png file too, as the file sizes of all of my inserted png files is being increased significantly by Storyline too. (It sure would be nice if Storyline did not increase the size of the mp3 AT ALL when adding to the project, as my project file is 4MB larger than it needs to be, because of that ONE file.)

I think the key here is that the software should not assume that it knows best when compressing files. I know exactly how each piece of media will be used in the project and I can compress them accordingly. I know Storyline is not adding any image quality to my png files, so there is no reason for it to increase the size of each one from 400KB to 700KB. Can you add an option to the compression settings so that files are left untouched when published? It would be even better if they were left untouched when inserted into the project.

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