Symbian/S60 audio playback rate

Question

I would like to control the playback rate of a song while it is playing. Basically I want to make it play a little faster or slower, when I tell it to do so.

Also, is it possible to playback two different tracks at the same time. Imagine a recording with the instruments in one track and the vocal in a different track. One of these tracks should then be able to change the playback rate in "realtime".

Is this possible on Symbian/S60?

Answer 1

It's possible, but you would have to:

1. Convert the audio data into PCM, if it is not already in this format
2. Process this PCM stream in the application, in order to change its playback rate
3. Render the audio via CMdaAudioOutputStream or CMMFDevSound (or QAudioOutput, if you are using Qt)

In other words, the platform itself does not provide any APIs for changing the audio playback rate - your application would need to process the audio stream directly.

As for playing multiple tracks together, depending on the device, the audio subsystem may let you play two or more streams simultaneously using either of the above APIs. The problem you may have however is that they are unlikely to be synchronised. Your app would probably therefore have to mix all of the individual tracks into one stream before rendering.