Output samples per second is 10 irrespective of the `preferredSamplesPerSecond` given

[thedroiddiv]

Describe the bug
Output samples per second is 10 irrespective of the preferredSamplesPerSecond given

To Reproduce
Steps to reproduce the behavior:

1. I'm using this helper class

object AudioManager {
    private lateinit var amplituda: Amplituda
    fun getAmplitudes(context: Context, audioFilePath: String): Pair<List<Int>, Long> {
        if (!::amplituda.isInitialized) {
            amplituda = Amplituda(context)
        }
        var amplitudes = listOf<Int>()
        var duration = 0L
        amplituda.processAudio(audioFilePath, Compress.withParams(Compress.AVERAGE, 50))
            .get({
                amplitudes = it.amplitudesAsList()
                Log.d("TAG", "getAmplitudes: ${it.amplitudesForSecond(1).size}")
                duration = it.getAudioDuration(AmplitudaResult.DurationUnit.MILLIS)
            }, { e ->
                Log.e("AudioManager::", "getAmplitudes: ", e)
            })
        return Pair(amplitudes, duration)
    }
}

Expected behavior
Expected Log: getAmplitudes: 50

Screenshots
If applicable, add screenshots to help explain your problem.

Smartphone (please complete the following information):

• Device: Google Pixel 6a
• OS: Android 14 (API 34)

[apkelly]

I'm also not seeing any change in the output list length for different input values in the preferredSamplesPerSecond.

[thedroiddiv]

Problem

I was recently debugging this issue with the latest version, found out that for higher preferredSamplesPerSecond=40, I am getting below error. Which is the basically falling back to the default FFMPEG frame size.

13:51:47.588  W  com.linc.amplituda.exceptions.processing.SampleOutOfBoundsException: Sample out of bound. Check `Compress` parameter: preferredSamplesPerSecond.
13:51:47.588  W  Read Amplituda doc here: https://github.com/lincollincol/Amplituda
13:51:47.588  W  	at com.linc.amplituda.AmplitudaResultJNI.getExceptionFromCode(AmplitudaResultJNI.java:108)
13:51:47.588  W  	at com.linc.amplituda.AmplitudaResultJNI.getErrors(AmplitudaResultJNI.java:84)
13:51:47.588  W  	at com.linc.amplituda.AmplitudaProcessingOutput.<init>(AmplitudaProcessingOutput.java:32)

My question, I am decoding an 44.1KHz audio, that means I can have at-most 441000 amplitude values per second, which is not the case here.

Reason

I was going through the code (haven't worked with JNI much though) and found something
The preferredSamplesPerSecond is being treated as number of frames per second, and frames are something specific to FFMPEG,

IDK how the frame_size inside FFMPEG is calculated, but this is not equal to sample_rate.

 if(audio_dec_ctx->frame_size > 0) {
        nb_frames = (audio_dec_ctx->sample_rate * (int) duration) / audio_dec_ctx->frame_size;
    }
 actual_frames_per_second = (int) (nb_frames / duration);
    __android_log_print(ANDROID_LOG_INFO, "Amplituda", "SampleRate: %d \t Preferred FPS %d: \t Actual FPS: %d \t Frame Size (samples per frame): %d",
                        audio_dec_ctx->sample_rate,
                        preferred_frames_per_second, // this is `preferredSamplesPerSecond`
                        actual_frames_per_second, // which cannot be more than this,
                        audio_dec_ctx->frame_size // coming from ffmpeg
    );

Produces Output:

SampleRate: 44100  Preferred FPS 1:  Actual FPS: 38   Frame Size (samples per frame): 1152

So my conclusion, using this method, maximum samples that we can get through this logic is: sample_rate/frame_size