cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   Steve Oldmeadow
   Administrator

   I've just checked in an important performance related change for CocosDenshion. Basically Apple's recommendation for best OpenAL performance is to have all your audio samples at the same sample rate and to set the audio mixer to the same rate.

   The default sample rate is 44100 Hz, however, if you need better performance it is recommended to use 22050 assuming you are happy with the sound quality. To use 22050 Hz execute the following code before any other audio code. This works with SimpleAudioEngine and CDAudioManager.

   [CDSoundEngine setMixerSampleRate:CD_SAMPLE_RATE_MID];

   Finally, CocosDenshion now has a CDConfig.h file that is analogous to cocos2d's ccConfig.h file. You can configure CocosDenshion using this file, importantly there is a CD_DEBUG define that is off by default - when it is enabled CocosDenshion will check and warn you about various things including whether it loads any files whose sample rate does not match the mixer sample rate.

   Posted 2 years ago #
2. 

   mhussa
   Member

   I know this is an obvious question but I'll ask anyway in case I've misinterpreted something.

   Isn't it possible to achieve the same affect by making sure all the source sounds files are stored as 22050? seems wasteful to store it at a higher rate only to down sample it. The only thing I can think of is a user performance setting in case they have problems on older devices otherwise use the higher quality samples.

   I noticed the CD_OS_3_PLUS setting which isn't referenced at all at the moment is this for future enhancements?

   Posted 2 years ago #
3. 

   Steve Oldmeadow
   Administrator

   Maybe I didn't explain clearly enough. For best performance have all your samples at the same sample rate and set the mixer to that same rate. However, 22050 will perform better than 44100 even though the native rate is 44100 because the mixer is having to do half as much work. This is based on information from Apple's WWDC 2009 OpenAL presentations.

   Yes, CD_OS_3_PLUS is for upcoming enhancements.

   Posted 2 years ago #
4. 

   mhussa
   Member

   OK I understand, You did mention it, but its this bit I didn't pay attention to.

   "...have all your audio samples at the same sample rate *AND* to set the audio mixer to the same rate."

   Thanks.

   Posted 2 years ago #
5. 

   zombie
   Member

   Does this also include the background music?

   Posted 2 years ago #
6. 

   Steve Oldmeadow
   Administrator

   @zombie - no it doesn't include the background music. I'm interested if this change makes any difference to the performance of ZombieSmash, since you guys have one of the most demanding games. It is a best practice recommended by Apple but many of their recommendations result in minor performance gains.

   As for background music, I don't have any recommendations. Since it is being decoded by hardware it is hard to know. I assume some software feeds the file to the hardware though so probably smaller files will be better for performance. From what people have posted on the forum it seems variable bit rate files should be avoided too.

   Posted 2 years ago #
7. 

   zombie
   Member

   Sound FX does not seem to have a notable performance impact. So we will probably not see increased performance, bet we are grateful for every small boost :)

   I am more interested in saving memory.

   We have mainly 22kHz samples. When having a CDenshion sample rate of 44kHz, will the smaller samples still take up the memory of a 44kH sample? So are they upconverted and then stored in memory?

   Posted 2 years ago #
8. 

   Steve Oldmeadow
   Administrator

   @zombie - no the amount of memory taken up by the samples depends only on the sample rate of the sound sample the mixer rate has no impact on memory.

   Posted 2 years ago #
9. 

   zombie
   Member

   ok, thx steve.

   Posted 2 years ago #

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