Audacity, an internationally popular audio recording and editing software, is a powerful cross-platform program built with an open-source implementation layered upon several libraries that allow for its dynamic development. It was originally written in 1999 by Dominic Mazzoni, a research student at Carnegie Mellon. University, as a platform on which to develop and debug audio processing algorithms. This kind of platform was novel at the time, because no concise and user-friendly way of tinkering with audio at such an advanced level existed for those aspiring to succeed in the music industry. Once released as open-source software, Audacity grew in popularity amongst developers and users alike »- its features were constantly being updated until it became what it is today: a powerful, complex, and community—driven program suitable for both professionals looking to easily edit their audio files and casual users dabbling in recording and simple editing.
A brief examination of its code would reveal that Audacity is layered on many libraries which aren’t crucial to its core features These libraries, such as LADSPA (Linux Audio Developer‘s Simple Plugin API) and VAMP API, enable Audacity to adapt and dynamically become more feature»rich as more and more plugins are developed for it. This design is reflective of the creator’s intention for Audacity to be an open—source software that anyone can easily modify and add features to. Other such libraries include libFLAC, libogg, and libvorbis, each of which provides access to audio compression formats, Though most of these supporting libraries are built-in to the distribution, some, like the LAME and FFmpeg libraries which provide support for the MP3 audio compression format, are barred by licensing restrictions to be added to the default distribution of audacity.
As such, those libraries along with some others that would enhance user experience and performance of the program must be dynamically loaded into the default implementation because of licensing. The structure and architecture of Audacity’s current implementation is also dependent on a very limited resource that plagues most community-driven, open»source projects with small developer teams like Audacity: developer time Because there is not enough time for Audacity’s development team to implement marginally useful features, these features are cut out entirely from design. This allows for better, more concise design -— focusing only on the essential goals of the software cuts out many potential security, performance, and compatibility issues at the small cost of a couple tangential features. Similarly, scripting has been implemented into the design by means of a single module and pipe, which allows a developer to write scripts in any language of his choice.
It would make very little programming sense to compile every scripting language in existence into the current implementation of Audacity to give the developers the same choice that the current modulerpipe structure does. As for the GUI of the program, the wxWidgets GUI library along with the ShuttleGui Layer facade takes care of the cross-platform visuals, The TrackPanel was also implemented to display the main panel ofAudacity, which shows the audio waveforms of the recorded data The actual audio data is recorded and played back using the PortAudio library, which allows for cross»platform audio recording and playback without having to implement the API for each separate operating system. Even without going into detailed analysis of these libraries, one can already tell that Audacity is a very versatile piece of software that transcends platform boundaries, and that ranks very high in terms of supportability.
As an interested prospective developer explores the depths of Audacity’s code, he will come to learn that the structure, being collaborative by nature, is often a jumble of messy code that is adaptable to contributors of varying skill levels. This is not to say that the code is bad by any means; the code is extremely well-written in some places, and in other places it is slightly redundant, repetitive, and suboptimal. Even so, the basic architecture of the software serves its purpose very well, and does not, in my opinion, require a change. The current implementation allows for a smaller learning curve for incoming developers, high compatibility with scripting languages, and a very high cross»platform supportability aspect. The layers of the program are also quite well—designed to optimize features and performance while still being compliant to licensing policies of various libraries crucial to Audacity‘s identity as an open-source project.
In terms of SOLID, Audacity’s architecture is very fitting for these set of principles of object-oriented programming. Classes in Audacity’s architecture, for the most part, have only one responsibility each. For example, the classes for buttons and TrackPanels, while both are part of the GUI and appear in the same interface, each do a single, distinct task — buttons are for interactivity between the end user and the methods of the program, while TrackPanel holds the responsibility of displaying end user data to the user using depictions of audio waveforms. The Open/Closed principle is very clearly seen in the current implementation ofAudacity — instead of modifying the classes every time someone wants to add a feature, the current architecture allows for very easy extension of the code using supporting libraries for dynamically loaded plugins and scripts.
The Liskov Substitution Principle is present in the code to a certain extent, but is not very relevant to this specific project. For example, many dialogue boxes in Audacity are modified instances of subtypes of the dialogue box provided by the wxWidgets Library that are copied and pasted withoutjeopardizing the integrity of the code. The interfaces in the code are properly segregated, so that the class for a dialogue box is separate from that for TrackPanel and do not depend on each other or each other’s methods, even though they share similarities in the GUI. Because of this, as far as wxWidgets is concerned, TrackPanel is only one component. In reality, TrackPanel comprises of various GUI elements and Audacity-specific code, and provides custom content for the application without the knowledge of separate classes and interfaces. GRASP principles are also very prominent in the current implementation of Audacity.
As described previously, interfaces are properly segregated, leading to substantially low coupling between classes — this is also a result of the High Cohesion of elements present in the software. Each element has a highly focused and singular task, as described above by the Single Responsibility principle. The Indirection Principle is applied in the addition of the ShuttleGui layer as a mediating factor between the wxWidgets GUI Library and the backing code in order to reduce coupling. The Controller, Creator, and Information Expert Principles are well-guided throughout the code; it is obvious which element controls which operation, which class/interface creates such an element, and which element has the information necessary for certain goals of the program The Protected Variations Principle, similar to the Open/Closed Principle in SOLID, is present through the easily extendable code and supporting libraries.
Track Panel itself, however, does not conform very well to these principles, as the current implementation has the GUI elements and application-specific code of TrackPanel horribly mixed together to create extremely messy and unoptimized program code. The current implementation creates many problems in customizability and abstraction, violating the SOLID principle of Dependency Inversion. It also hogs system resources when many widgets are drawn and repainted, requiring the system to access them by their handles The proposed solution to this issue is a flyweight design pattern in lieu of the current ad-hoc pattern This, along with the self- drawn and self-contained widgets using an API similar to that of wxWidgets with custom sizers and components, would allow for minimization of system resource use and extremely clean and concise code.
Functionally, Audacity is a fantastic program. All of its core functions work as they should, and the many plugins that are supported by its backing architecture make using it a pleasurable, feature-rich experience. It is also extremely usable — a first-time user would have no problem at all navigating its simple interface and using its features effectively, especially with the great documentation provided. Granted, the editing and applying of sound effects may have a bit of a learning curve, but that is more of an issue of personal skill rather than usability, Audacity is also a very reliable program that is, by design, very stable, and very rarely fails while performing operations, Thanks to its BlockFiles solution of managing data, Audacity is also a high-performance program that is very efficient in inserting and deleting elements from audio files that may be many hours long. The solution also allows for displaying cached summary information in order to further save system resources, and in effect, create a faster, more efficient program
Supportability isn’t even a question; Audacity is fully crosseplatform, allows for dynamic loading of plugins due to the immense amount of supporting libraries, and is compatible with any scripting language of the developer’s choice due to the module-pipe structure it implements To the end user, Audacity seems to be a very unified, consistent, and well-designed program almost to the point of perfection. While it is true that it is quite an efficient, feature-rich, and functional piece of software that is compliant with good programming principles for the most part, Audacity has run into many design and performance problems since its advent that have still not been ironed out. Despite these few inevitable performance and programming qualms, Audacity has a very proficient and functional design that caters to both the open-source development community and the end user. Perhaps the issues that still exist in its design will be solved in a powerful, collaborative effort that the open-source model permits.
