Audio Optimization Guide

Required Packages

Install gsutil

Go to the gsutil installation page.
Select the operating system and platform that matches your computer and download the appropriate file.
Open your terminal and navigate to the directory where you downloaded the uncompressed file. For example:
```
cd Downloads
```
Run the installation script:
```
./google-cloud-sdk/install.sh
```
- Say yes to any prompts during installation.

Install Homebrew

Open your terminal and run the following command:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

After the installation completes, install wget by running:
```
brew install wget
```

Copying Files from the Bucket

Create a folder on your computer where you want to store the assets. In your terminal, use:
```
mkdir New-Assets
```
Replace New-Assets with your desired folder name.
In your browser, navigate to the bucket containing the assets you want to download.

Select the assets you want to download and click the DOWNLOAD button. It should look something like this:

gsutil -m cp \
    "gs://roar-swr/es/shared/ROAR-Palabra Instructional Video.mp4" \
    "gs://roar-swr/es/shared/arrow_left_p2.mp3" \
    "gs://roar-swr/es/shared/arrow_left_p2.mp3" \
    "gs://roar-swr/es/shared/arrow_p3.mp3" \
    "gs://roar-swr/es/shared/arrow_p3.mp3" \
    "gs://roar-swr/es/shared/arrow_right_p2.mp3" \
    "gs://roar-swr/es/shared/arrow_right_p2.mp3" \
.

Copy the provided command for downloading the assets.
In your terminal, navigate to the folder you just created:
```
cd New-Assets
```
Paste the copied command into your terminal and press Enter.

Optimize Audios

In the same folder where the assets were created, create a new folder for the desired output bitrate. For example, for 32 kbps:
```
mkdir output-32
```
Use the following command to convert the MP3 files to the specified bitrate and store them in the new folder:
```
for fn in *.mp3; do ffmpeg -i $fn -map 0:a:0 -b:a 32k ./output-32/$fn; done
```

Note

Repeat the optimization steps for different bitrates (e.g., 64, 96, 128 kbps) by creating separate output folders and adjusting the bitrate in the ffmpeg command. For example, for 64 kbps:

mkdir output-64
for fn in *.mp3; do ffmpeg -i $fn -map 0:a:0 -b:a 64k ./output-64/$fn; done

Suggested Recommendations

We recommend using 32k for audio instructions, and at least 96k for stimuli