How to convert a WAV file into a 3gp in Android using MediaCodec

Question

I have tried to perform the with the following conversion loop.

    while (true) {
        sampleSize = extractor.readSampleData(inputBuffer, 0)
        if (sampleSize < 0) break
        val presentationTimeUs = extractor.sampleTime
        val flags = extractor.sampleFlags

        val inputBufferId = codec.dequeueInputBuffer(codecTimeoutUs)

        if (inputBufferId >= 0) {
            val codecBuffer = codec.getInputBuffer(inputBufferId)
            codecBuffer?.put(inputBuffer)
            codec.queueInputBuffer(inputBufferId, 0, sampleSize, presentationTimeUs, flags)
        }

            extractor.advance()
       

        val outputBufferId = codec.dequeueOutputBuffer(bufferInfo, codecTimeoutUs)

        if (outputBufferId >= 0) {
            val codecBuffer = codec.getOutputBuffer(outputBufferId)
            muxer.writeSampleData(outputTrackIndex, codecBuffer!!, bufferInfo)
            codec.releaseOutputBuffer(outputBufferId, false)
        }
    }

The results are a an invalid .3gp file, can you help me?.