Audio Sample Rate Changes After Publishing
Hi Storyline community,
I'm having a quality issue with the audio that is published from Storyline, which I'm fairly sure is due to Storyline changing the sample rate of the audio to 22050 Hz while publishing. I've searched the community, but have only found discussions related to the audio bit rate in the Publish Quality settings, which is something different altogether.
This seems to happen regardless of audio format input into Storyline (mp3, wav, etc), as well as the sample rate and bit rate of the input audio. Changing the bit rate in the publishing settings does not seem to affect the sample rate either.
My question is this: Is there any way I can change how Storyline handles the sample rate on publishing?
One solution: I can replace the published audio files with the pre-Storyline original audio, but this is not practical for projects with lots of audio, especially because Storyline randomizes all of the published filenames. I'm hoping there is a better way to do this. Maybe this needs to be a feature request.
For those interested, here are some technical details about the issue, and an explanation of why this is a problem.
It appears that the audio files are changed to a sample rate of 22050 Hz upon publishing, which is exactly half of the CD-quality standard of 44100 Hz. This is a big deal, because it truncates much of the high frequencies in the audio. Without going into details about Nyquist's Theorem, a sample rate of 22050 Hz implies that all frequencies above 11025 Hz are cut off.
By cutting the higher frequencies, the audio loses a lot of the "air" and "brilliance" on professionally recorded voiceovers. It's even worse for music, which tends to use the full spectrum of human hearing (roughly 20Hz to 20kHz).
I've added the following attachments to show the results:
- Before_Storyline.mp3 (This is the source audio before being added to Storyline - 128kbps 44100 kHz)
- After_Storyline.mp3 (This is the audio published by Storyline using 128kbps publishing quality - 128kbps 22050 Hz)
- Before_and_After.png (This shows the difference between the two audio clips on a spectogram. Note how the second clip is chopped off around 11kHz.)