Question

I need to implement a playback of separate audio files in N channels, files may play sequentially or in parallel. I need to implement it on Android.

Timeline:

|file a…|file d….|file b…|……|file k|….

|…..|file g|file c..|file p.|….

I’m thinking two options, one being FMOD to decompress files and play them simultaneously. I have researched and FMOD seems to fit well and much easier than manually playing this using an AudioTrack. However, I can’t understand if FMOD would allow us to save the entire merged output without playing it through.

I know that using solution here we can redirect output to a wav file, but is it possible to just create a final output instantly and save it using FMOD? Or will I have to manually merge PCMS into one stream after all..

Thanks.

Answer 1

An important question here is why you need to save the files out, if it’s possible to do this offline then it would be a lot simpler. If you must record the concatenation of several files (including others played in parallel), it is quite possible with FMOD.

One way would be to use wave-writer-nrt output mode, which allows you to output a wav file based on FMOD playsound calls in faster than realtime.

Another way is to use a custom DSP to access the data stream of any submix as it plays, useful if you want other sounds actually playing at the same time.

Another is simply create the sound objects, then use Sound::lock to access the PCM data, which you could concatenate yourself to a destination. Keep in mind all the sounds would need to be the same sample rate and channels, otherwise you would need to do processing. Also keep in mind you cannot do this for parallel sounds unless you want to mix the audio yourself.