Optimum audio size

Scripture App Builder
1

Hi all, I am wondering how many kbps your audio (mp3) files are. Is there a recommended and/or optimum size?

I am trying to get the right balance between sound quality and not-too-big audio files which take up a lot of room on people’s devices and/or take too much time to download from the internet, especially in more isolated areas with poor internet connectivity.

Thanks.
Roselle

2

I tried a number of CBR (constant bit rate) data rates, and found that 48 kbps mono gave fine quality for voice, with very little noticeable difference from 64 kbps.

Because we wanted to package one Gospel (Matthew) in the app, and we wanted the app download to be less than 25 MB, we reduced Matthew to 16 kbps. This is a compromise, and it’s not as “listenable” as 48 kbps.

One of the feature requests I’ve communicated for SAB is that, in an app like ours, the user could still download the 48 kbps.

3

Thanks! I’ll try 48 and see how it sounds. :slight_smile:

4

I’ve just started working with this. I was wondering if you have been using the 48 kbps mono. If so, how are you finding the audio quality at that setting?
Thanks.

5

Hi Roger,

Thanks for asking! We’ve settled on 64kbps. That seems to be the sweet spot for us.

6

Roger and @Roselle_Dobbs, our team has decided on a smaller size MP3 with a constant 24 kbps mono at 16,000 Hz. At this bit rate the whole New Testament with Genesis and introduction files is almost exactly 400 MB.

We of course can’t package all of that in the app on the Play Store, but at least that way the audio files don’t take up as much space on people’s phones. I’m not sure about your context, but here in West Africa I find that many people phones are almost completely at capacity and they have to go delete apps and/or media before they can even install any scripture app. I suspect that the default WhatsApp settings, in conjunction with their practice of exchanging video and audio files, are what make it so that people’s phones are so easily filled with media.

7

Hey Andy,

Thanks for the reply. We’ve done a few more recordings and are starting to get them integrated into SAB.
I suspect that the default WhatsApp settings, in conjunction with their practice of exchanging video and audio files, are what make it so that people’s phones are so easily filled with media.
Yes, definitely the case here in Asia Pacific as well.

With those settings for the mp3 files, have you noticed any major sound quality issues? Are all the phones that able to play those clear enough?

Thanks

8

We have not had any phones that can’t play the MP3 audio files. I think the playing of the audio files is actually managed by the SAB.

One thing we are considering to do is to create individual apps for each book of the New Testament, then include the audio in the APK file. That way they can listen to the whole book, then just download a new app when they want to listen to a new book. Not at all ideal for listening to the whole NT, but it would give people a taste for the scriptures then potentially motivate people to carve out some space on their phone, or at least install it first on a new phone before it is full of other media.

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Individual apps for the different books…That’s an interesting idea. We might need to look into that as well. Thanks!

10

In SAB 9.1, we will be supporting WebM audio in Android 4.1+. If the audio doesn’t have music, I believe the 16Kbps WebM sounds at least as good as 64Kbps MP3 at about 1/3 the size.

You can now use SAB 9.0.1 to compress your current MP3s and do the comparison. I would really appreciate you feedback on the quality. See this post on how to do the conversion using SAB:
SAB 8.5: Ogg Opus / WebM Audio

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