Empty Output on iOS with “TensorFlowLiteTaskAudio 0.4.3” and “TensorFlow Lite Model Maker Model”

[ghashi]

TLDR:

on iOS, when calling classify (a.k.a let results = try classifier.classify(audioTensor: inputAudioTensor)) on a model created using “TensorFlow Lite Model Maker”, then results.classifications[1].categories is always empty (in my case it was expected to output maximum of 5 values)

I think there’s a bug on pod “TensorFlowLiteTaskAudio” because the same model works as expected on Android.

Sample repository to reproduce this bug : https://github.com/ghashi/tensor-flow-lite-task-audio-poc

Long version

I created a model using "TensorFlow Lite Model Maker Model”

I followed this tutorial https://www.tensorflow.org/lite/models/modify/model_maker/audio_classification and created a .tflite model that recognizes 5 kinds of birds songs. Here’s the versions I used to create it:

Python 3.7
Numpy Version: 1.21.6
TensorFlow Version: 2.9.3
Model Maker Version: 0.4.2 (and 0.3.4)
portaudio: stable 19.7.0

Then, I integrated this model into an Android and an iOS application. I used the tensorflow “audio classification demo” repository to do this.

Android works ✅

The Android app works fine. In other words, when I execute

tensorAudio.load(recorder)
val output = classifier.classify(tensorAudio)

then:

• output[0].categories has a maximum of 521 values (as expected)
• ouput[1].categories has a maximum of 5 values

the image below show a screenshot of the app (left) and a debugging session(right) that shows the values mentioned above.

iOS doesn't work ❌

The iOS app doesn’t work as expected. In other words, when I execute

try inputAudioTensor.load(audioRecord: audioRecord)
let results = try classifier.classify(audioTensor: inputAudioTensor)

then:

• results.classifications[0].categories has a maximum of 5 values ([the expected value is 521)
• results.classifications[1].categories is always empty (the expected value is 5)

the image below show a screenshot of the app (left) and a debugging session(right) that shows the values mentioned above.

ps1: I'm using TensorFlowLiteTaskAudio 0.4.3 ps2: the iOS app works fine when using the default yamnet model. You can see in the image below that results.classifications[0].categories has a maximum of 521 values (as expected)

Question

Is there a bug on the pod “TensorFlowLiteTaskAudio”? Or is there some special configuration that should be done on iOS when integrating a model generated by “TensorFlow Lite Model Maker”? Or should I change something when generating the model .tflite for iOS?

Steps to Reproduce

1. create a a model using “TensorFlow Lite Model Maker”
2. integrate this model into an iOS app
3. run the app
4. the model is expected to return some results but it always returns an empty array

ps: I created a repository to help you reproducing this behavior. It shows:

• how the model .tflite is created
• how it is integrated on Tensor flow iOS “audio classification” demo code
• how it is integrated on Tensor flow Android “audio classification” demo code

This is the link: https://github.com/ghashi/tensor-flow-lite-task-audio-poc . If you want to use it:

1. clone it
2. create your own model using model-generator/model_maker_audio_classification-toreport.ipynb or just skip this step
3. run the ios app (folder ios)
4. select “birds”
5. debug line 162 of ios/AudioClassification/TFLite/AudioClassificationHelper.swift
6. check the variable “results” on the debugger