Is cocosDenshion capable of doing this?

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Is cocosDenshion capable of doing this?

(11 posts) (4 voices)

Started 1 year ago by marcotronic
Latest reply from marcotronic

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marcotronic
Member

Hi,
I´ve already read the FAQs and the cookbook in the wiki and had a look at the example apps that come with cocos2D but I haven´t found the asnwer yet. Maybe you can help me...

For my current project (interactive children´s book for the iPad) I need the following features (basically different "layers" of audio):

- Background music (okay, so far no problem with cocosDenshion, I´ve got some examples of using background music and how to fade out and in, but here comes my question: Can I crossfade two pieces of background music? When the user switches the scene I want to fade out the background music of scene 1 and simultaneously fade in background music of scene 2 (without a break/silence in between).

- speech (voice over) - Here I plan to use the foreground music stuff in cocosDenshion (I guess it´s possible to play background music and use foreground music for the voice over?

- sound effects (when the user touches certain sprites/areas I want to play sound FX) - for that I use the sound effects in cocosDenshion, right?!

- an ambient sound layer (backgorund ambience, nature etc...) - what could I use here?

The user should be able to switch off the speech layer at least. So this definitely has to be a separate "track"/layer. I could possibly mix the backgound music and the ambience sound layer myself and use one already mixed audiolayer ot this (but then it´s important for me to do that crossfade thingy... see above)

I´m grateful for your help/ideas whatsoever...

Thanks a lot in advance,
Marco

Posted 1 year ago #
Steve Oldmeadow
Administrator
-Background music: yes you could crossfade two pieces of background music. By default the "left" CDLongAudioSource is mapped to backgroundMusic but the "right" one can be used for background music too. However, only one CDLongAudioSource can be decoded by hardware, the other will be decoded in software which incurs a performance penalty. Follow Apple's recommendation and use .aac files for your compressed audio as these have a lower software decoding overhead than .mp3.

- Speech: it really depends on how long it is. If you use effects it could chew up a lot of memory. You could use a CDLongAudioSource for speech too, you could easily modify CDAudioManager to have 3 or more CDLongAudioSource objects. You could also just manage your own AVAudioPlayer object for speec.

- Sound Effects: yes just use playEffect

- Ambient Sound Layer: similar issues to speech really. It depends on how long it is.

You use audioSourceForChannel to get hold of the CDLongAudioSource objects. e.g. this code will get you the "spare" object, kASC_Left is mapped to backgroundMusic.
```
[[CDAudioManager sharedManager] audioSourceForChannel:kASC_Right];
```
Hope that all makes sense. If it doesn't just ask.
Posted 1 year ago #
marcotronic
Member

Thanks a lot, Steve!

When you say that there are "right" and "left" audio sources - does that mean they are mono? Or can I play stereo music with each right and left audio source?

The speech for my first project is about 3,5 minutes long but I would only load and play chunks that are about 20 seconds or so long (imagine there is a paragraph of text that is read aloud, then the user clicks and the next paragraph is displays and read by the speaker), the speech is mono, of course.

Okay, I will have a closer look into your sources. I just wanted to ask if what I have in mind is possible at all... :o)

I will have to see what´s going on performance wise... There won´t be too much action (I hope so :o)) ). Just some full screen background images for the scenes, some layers of text (maybe bitmap fonts, maybe images, I´m not sure at the moment - with images I have more creative freedom) and some animated sprites here and there. And all the audio stuff, of course...

Thanks a lot
Marco

Posted 1 year ago #
Steve Oldmeadow
Administrator

The "left" and "right" are just arbitrary names for the two sources, both sources can be stereo.

20 second chunks of speech should be okay as effects if you unload the speech once you are finished with it.

If you are just targeting the iPad I think you'll be okay.

Posted 1 year ago #
eoin
Member

ok, am in similar position. I need background music and continuous effects. I take it I should not use PlayEffect?

So if I use this [[CDAudioManager sharedManager] audioSourceForChannel:kASC_Right];

I can play continuously in two channels? Correct?

Posted 1 year ago #
Steve Oldmeadow
Administrator

@eoin - I don't understand what you mean by continuous effects. The main determinant of whether you use effects or CDLongAudioSource is the length of the audio sample. CDLongAudioSource is intended for long duration audio where it would be impractical for memory reason to load the audio into a static buffer. Of course, what is practical from a memory perspective depends on what devices you are targeting and how much memory your app is using for other things.

Posted 1 year ago #
popgoblin
Member

...well, now that we're discussing whats possible with CocosDenshion, i'll risk hi-jacking the thread ;)

Is it in anyway possible to introduces "filters" to the sounds, played by CocosDenshion? Like echos, reverb, low-pass etc. ?

I'm using FMOD today for that - but as far as I can see, the only real benifit over engines like CD is the DSP processing....

best regards,
Morten

Posted 1 year ago #
Steve Oldmeadow
Administrator

No, CocosDenshion can't do things like that.

Posted 1 year ago #
marcotronic
Member
Hi Steve,
thanks a lot.

Now I want to play two separate tracks of background music... I start with the SimpleAudioEngine like in the examples:
```
sae = [SimpleAudioEngine sharedEngine];

[sae preloadBackgroundMusic:@"bgm.mp3"];

[sae setBackgroundMusicVolume:0.3f];
[sae rewindBackgroundMusic];
[sae playBackgroundMusic:@"bgm.mp3"];
```
Later on I fade out the music like in your example:
```
[CDXPropertyModifierAction fadeBackgroundMusic:5.0f finalVolume:0.0f curveType:kIT_Exponential shouldStop:YES];
```
So in order to play background music I don´t touch the CDAudioManager directly. How can I tell the SimpleAudioEngine to play the background music with the kASC_Right or kASC_Left channel? And how would I use the CDXPropertyModifierAction to fade the music on the left or right channel?

Do I have to play the background music differently (not using the sae ?)

Thanks a lot for your help in advance,
Marco
Posted 1 year ago #
Steve Oldmeadow
Administrator

You can't do what you want to do with SimpleAudioEngine alone. It is fine to mix the usage of SimpleAudioEngine and CDAudioManager (except for loading of effects - only use one or the other).

"backgroundMusic" is mapped to kASC_Left by default. There is no way to specify backgroundMusic is on the left or the right. If you look at all the backgroundMusic methods you will see they are very simple wrappers around CDLongAudioSource methods and it is very simple to work with CDLongAudioSource objects directly.

The fadeBackgroundMusic method is just a convenience, if you look at the implementation you will see it is very easy to write your own fadeMusic method that could take a channel constant as a parameter.

So long story short, don't use any *backgroundMusic methods work directly with CDLongAudioSource.

Posted 1 year ago #
marcotronic
Member

Thank you very much, Steve. It´s getting clearer now :o)

Marco

Posted 1 year ago #

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