https://github.com/bearinmindcat/Equalizer314/compare/Equalizer314-v0.0.3-beta...Equalizer314-v0.0.4-beta/

To start, there are no truly "free" and/or "open source" alternatives to Wavelet and Poweramp EQ. After using both of those apps, among various other EQ apps, significant shortcomings were found in terms of the features and accessibility they offer. The development of this app began with the goal of having both a powerful parametric EQ function and minimal permissions. This is why both the DynamicsProcessing and Visualizer APIs are used as the framework for the app, as only minimal permissions are required for them to work in tandem. There are shortcomings from both APIs, but these will be discussed later. This app is built off the DynamicsProcessing API. More information about the documentation and features it offers can be found here (https://developer.android.com/reference/android/media/audiofx/DynamicsProcessing). This is the same API that Poweramp EQ and Wavelet both use, but in some aspects, they were not really able to squeeze out the maximum potential that this API can offer. Coming from the audio production and IEM world, there is a deep understanding of what both sides want. The goal was to take advantage of both to create something that meets creative endeavors. Using the Visualizer API, the aim was to give users a way to reliably cross-reference visual data with audio data. This is useful for the main EQ portion, as audio changes can be visually referenced, but it becomes even more important with the Limiting and Multiband Compression sides of the app. While these features are available in the DynamicsProcessing API (and many apps like Poweramp EQ and Wavelet premium-lock these features), they simply add knobs/sliders and expect the user to understand exactly how they work. Without real audio-visual feedback, users cannot take advantage of these features to their full potential. This is the reason why many DAWs and VST plugins use audio-visual feedback with these functions specifically. By using the Visualizer API with these DynamicsProcessing features, an intimate audio-visual feedback loop is created, giving complete control over the audio framework. Shown below are some screenshots of the Multiband Compression and Limiter, and how the Visualizer API functions with the input curves, GR trace curves, and the limiter waveform metering. For many other functions that do not use the Visualizer API, correct visual feedback (using the same style implementation that many DAWs use) was still a priority. Examples include the compressor and attack/release visuals. Values can be changed independently with the slider and by moving a finger along the line/graph itself. This occurs in other places in the app as well, but these are two good examples. Why DynamicsProcessing & Visualizer APIs? Other apps and methods for device EQ and visualization exist, but the choice of DynamicsProcessing and Visualizer as the framework for this app (versus other available options) requires explanation. To reiterate, the DynamicsProcessing API was chosen—the same API that popular apps such as Poweramp EQ and Wavelet use—because it offered enough tangibility compared to what would have to be sacrificed by using other, more powerful methods. Other methods of EQ available (ranked): Android's built-in Equalizer class (android.media.audiofx.Equalizer) - Fixed amount of EQ bands. This is what many "lazy" EQ apps use, along with other apps that want to use EQ but do not want to focus on building an EQ engine (audiobook apps, music players, media players, video players, etc.). - Attaches to an audio session. AudioEffect API subclasses (https://developer.android.com/reference/android/media/audiofx/AudioEffect) - Much better than Android's built-in Equalizer class but still lacks in comparison to DynamicsProcessing. - Many apps are built with DynamicsProcessing and AudioEffects, as there are some subclasses within the API that can offer "different" features that DynamicsProcessing cannot, and they can attach to the same audio session pipeline. - Attaches to an audio session. AudioPlaybackCapture (RootlessJamesDSP) - Has much more access to the audio framework than any of the available APIs above, but in order to do so, ADB permissions (using something like Shizuku) must be granted. This method would also provide a much more accurate Visualizer/Spectrum, but it would force the use of the RECORD_AUDIO permission while also increasing audio latency. Keeping permissions in this app as low as possible was a priority, and a well-developed app using this method already exists, so creating something already done was avoided. - Another limitation is that some apps, such as Spotify, block internal audio capture. AudioFlinger (JamesDSP & ViPER4Android) - This is the "best" method for full control over audio without latency issues. There is no "down-side" to using this method other than requiring a rooted device, which steers many people away. This method, along with RootlessJamesDSP, is best used to apply custom audio effects directly without relying on Android's built-in effects. - Only con? Root. Presets, EQ Generation & AutoEQ Many apps run AutoEQ (https://github.com/jaakkopasanen/AutoEq/wiki/Choosing-an-Equalizer-App), including Wavelet and Poweramp EQ. What those apps do not offer are either free access to AutoEQ (common, Wavelet...) or the use of the built-in AutoEQ algorithm from the AutoEQ GitHub, which can be reviewed here (https://github.com/jaakkopasanen/AutoEq/wiki/How-Does-AutoEq-Work%3F). This algorithm is used in the "Generate Custom EQ" section of the app; a "measurement" and a "target" are required, both of which can be taken from squig.link and various online resources. On top of this, maintaining homogeneity between preset sharing among popular equalization "applications" is important. This is why APO was chosen as the main export method rather than an independent export method like those used by Poweramp EQ and Wavelet (also shown below in the "Generated EQ" portion). This allows the exported APO file to be transferred to desktop equalization software (EqualizerAPO) without conversion issues. Creating a conversion software within the app or on this GitHub was considered, so that users wanting to transfer from Wavelet and Poweramp EQ could do so with ease. This might be implemented later if many users request it. Known Issues This app specifically uses session 0 for all applications, unlike Wavelet and Poweramp EQ, which attach themselves to an audio session. In the future, an option to attach to individual audio sessions (like the latter apps) may be provided, but as of the v0.0.1-beta release, there is no ability to do so. As for conflicts, as long as another app is using session 0, this app's EQ will not work; only one app can control session 0 at a time. An auto-reclaim feature was added to the code that will attempt to take over session 0 if another app takes it over, but this will not always work, and brief audio glitches or dropouts may be experienced while this is happening. These same issues occur with Wavelet, RootlessJamesDSP, Poweramp EQ, and most other EQ apps, as they all target session 0. License GNU General Public License v3.0