A fast, easy to use, free, and community supported 2D game engine
JohnM
Member
Hi,
I have some music in wav format. I am not sure about using mp3 as I am not sure does it impact peformance.
What format is best to use so that it does not lower performance?
1. Wav format takes so much space (20MB). Can this be reduced somehow?
2. Is there some other file format than wav that is smaller in size and will not reduce performance?
Can someone advise?
Thanks in advance
I use caf which is 1/4 the size but still sounds great. Check out this article:
http://www.wooji-juice.com/blog/iphone-openal-ima4-adpcm.html
I like IMA4 as well, it's also very easy to process (almost as easy as wav). Besides that make sure to make the source file as small as possible. Reducing the samplerate to 22050 Hz and using only one channel (mono) still give me acceptable results for the music.
Steve Oldmeadow
Administrator
JohnM
Member
@Karl and @Steve Oldmeadow
Ok, is it by using Ambient Solo as explained here: http://www.iphonedevsdk.com/forum/iphone-sdk-development/38133-my-music-file-way-too-big-uncompressed-caf-but-if-i-compress-game-lags.html
Is there some switch that tells to use hardware to play music file?
Is it better to convert compressed music (lets say mp3) to 64kbit or 96kbit (smaller size). Does it help in term of performance?
As for sound effects, I can use wav file, right? This will be played by using processor.
Although I'm not Steve, I think I can answer your questions.
@JohnM
The audio session category of your app determines if you can use the hardware path or not. Every category that allows other audio (like the ipod) to mix with yours, can't use the hardware path.
In general, the less audio data you need to transmit, the better performance will be. I wouldn't make the bitrate too low, but lower the samplerate and channels so the uncompressed audio is smaller in size.
For sound effects, I would recommend IMA4, see the link mentioned at the bottom of this post for more information. Again make them as small as possible for optimal performance. I used 8-bit 16000 Hz, mono sound effects for my last game.
@wmwilson
Apple still recommends IMA4 for playing multiple sounds at once (link).
Steve Oldmeadow
Administrator
@JohnM - refer to Session 412 of the WWDC 2010 sessions for details of how hardware is allocated but basically hardware is assigned on a first come basis to apps with non mixable audio session categories.
For sound effects you can use wave files but they must use little endian encoding.
@wmwilson - since this is the CocosDenshion support forum I'll assume you are talking about CocosDenshion. In which case the sound format is largely irrelevant for sound effects. All sound effects are loaded into memory and played back in linear pcm format. aac, ima4 and mp3 files will just be converted at run time. The only thing using one of these formats for sound effects buys you is a smaller file size for your app.
Essentially:
Any mode that uses mixing (such as ambient sound) will automatically use software decoding, even if the hardware decoder is idle.
Any mode that doesn't use mixing (such as solo ambient) will use hardware decoding if it's available. When two AVAudioPlayers play music simultaneously in this mode, the one that started playing first will use hardware decoding, and the other will use software.
The advantage of mixing is that it allows other applications (such as ipod) to continue playing while your app is running.
v3nom
Member
Hi:
I'm trying to convert a wav file into caf-ima4. I'm using afconvert like this:
afconvert -f caff -d ima4@44100 -c 1 -b 128000 audio.wavBut it shows an error that says:
Error: Couldn't set audio converter property ('who?')If I remove the "-b 128000" the conversion process is finished without errors, so how can I specify the bitrate correctly?
Thanks! :D
tetraweb
Member
I found this to be a great simple explanation of best practices:
http://www.sparrow-framework.org/2010/06/sound-on-ios-best-practices/
Greg
Steve Oldmeadow
Administrator
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