Extension files, Google Play, and Compression

Solar2D Android
#1

When using extension files and uploading to google play I get a warning:

APK expansion file might be highly compressible. Compressing with zip -9 could significantly reduce its size: the first 50.0 MBs were found to be 34.29% compressible.
Ignore this warning if you have optimized for memory/performance. See Using the APK Expansion Zip Library for more information.

Since my current extension file is just under 300mb, I could see this as a huge savings.

Is there some setting I can turn on to take advantage of this? Or is google play incorrectly analyzing something?

#2

Google is not wrong.  By default, Corona does zero compression on expansion files for performance reasons.  I remember testing this before and loading an image from a compressed expansion file would typically take 3x longer compared to an uncompressed expansion file.  That’s a huge difference.  Meaning that you probably don’t want your app to take 3x longer to load, because odds are that’s what will happen.

Besides, most of the files formats you are likely using such as PNG, JPEG, OGG, MP3, etc. are already naturally compressed file formats.  This is what matters most.

If this does matter to you, then you could unzip the expansion file (it’s really just a zip file) and then re-zip it with compression.  Just be prepared for slow startup times.

#3

Google is not wrong.  By default, Corona does zero compression on expansion files for performance reasons.  I remember testing this before and loading an image from a compressed expansion file would typically take 3x longer compared to an uncompressed expansion file.  That’s a huge difference.  Meaning that you probably don’t want your app to take 3x longer to load, because odds are that’s what will happen.

Besides, most of the files formats you are likely using such as PNG, JPEG, OGG, MP3, etc. are already naturally compressed file formats.  This is what matters most.

If this does matter to you, then you could unzip the expansion file (it’s really just a zip file) and then re-zip it with compression.  Just be prepared for slow startup times.