README.md

MP3-Downloader

Youtube to MP3 Coverter app

📷 Previews

Download apk

Demo video 📹

🛠 Tech Stacks & Open Source Libraries

• Jetpack Compose
• ViewModel
• Hilt
• Moshi
• Chaquopy : To create an environment to run .py script
• mobile-ffmpeg : To convert .m4a to mp3
• yt-dlp : To download .m4a audio from youtube

⭐ Key features

• Grabbing & Downloading : Chaquopy used to create an environment for running main.py. It contains get_video_info() to grab video info and download_audio() to download m4a audio. During download, it also returns invokes a callback to log progress on Android side.
• Converting Ffmpeg command to convert file

ffmpeg -i $inputFile -c:v copy -c:a libmp3lame -q:a 4 $outputFile

• Saving: Input and output streams used

🤔 Key challenges faced

• UI related
  ❓ Creating multiple screens vs single screen
  ❓ Architecturing the UI for different steps
  💪 Solution: Broke down the UI into state machine. During a session, the app is always in one of the following HomeScreenStep

• yt-dlp related
  ❓ How to use yt-dlp (python) in Android project
  ❓ Understanding yt-dlp and creating script for it
  ❓ How to send progress of download to Android
  💪 Solution: Used Chaquopy and yt-dlp's doc

• ffmpeg related
  ❓ How to use ffmpeg in Android project
  ❓ Ffmpeg command to convert file
  💪 Solution: Used mobile-ffmpeg and ffmpeg's doc

⭐ Possible Improvements

• Could have added tests
• Could have polished the UI

File structure

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MP3 Downloader
│   AndroidManifest.xml
│
├───java
│   └───com
│       └───example
│           └───mp3downloader
│               │   App.kt
│               │   MainActivity.kt
│               │
│               ├───data
│               │   └───model
│               │           DownloadProgressInfo.kt
│               │           VideoInfo.kt
│               │
│               ├───di
│               │       AppModule.kt
│               │
│               ├───presentation
│               │   ├───common
│               │   │   │   DestinationFolderItem.kt
│               │   │   │   DownloadButton.kt
│               │   │   │   ScreenHeader.kt
│               │   │   │   TextFieldItem.kt
│               │   │   │   VideoInfoItem.kt
│               │   │   │
│               │   │   └───step_content
│               │   │           ConvertingStepContent.kt
│               │   │           DownloadingStepContent.kt
│               │   │           FailureStepContent.kt
│               │   │           SavingStepContent.kt
│               │   │           SuccessStepContent.kt
│               │   │
│               │   └───home_screen
│               │           HomeScreen.kt
│               │           HomeScreenEvents.kt
│               │           HomeScreenState.kt
│               │           HomeViewModel.kt
│               │
│               └───ui
│                   └───theme
│                           Color.kt
│                           Theme.kt
│                           Type.kt
│
├───python
│       main.py
│
└───res
  ├───drawable
  │       ic_launcher_background.xml
  │       yt_logo.png
  │
  ├───drawable-v24
  │       ic_launcher_foreground.xml
  │
  ├───font
  │       plus_jakarta_sans_bold.ttf
  │       plus_jakarta_sans_semibold.ttf
  │
  ├───mipmap-anydpi-v26
  │       ic_launcher.xml
  │       ic_launcher_round.xml
  │
  ├───mipmap-hdpi
  │       ic_launcher.webp
  │       ic_launcher_round.webp
  │
  ├───mipmap-mdpi
  │       ic_launcher.webp
  │       ic_launcher_round.webp
  │
  ├───mipmap-xhdpi
  │       ic_launcher.webp
  │       ic_launcher_round.webp
  │
  ├───mipmap-xxhdpi
  │       ic_launcher.webp
  │       ic_launcher_round.webp
  │
  ├───mipmap-xxxhdpi
  │       ic_launcher.webp
  │       ic_launcher_round.webp
  │
  ├───values
  │       colors.xml
  │       strings.xml
  │       themes.xml
  │
  └───xml
          backup_rules.xml
          data_extraction_rules.xml