HomeMobileSmule Adopts Google’s Oboe to Enhance Recording High quality & Completion Charges

Smule Adopts Google’s Oboe to Enhance Recording High quality & Completion Charges

Posted by the Smule Engineering workforce: David Gayle, Chris Manchester, Mark Gills, Trayko Traykov, Randal Leistikow, Mariya Ivanova.

Light blue graphic with karaoke elements

Govt Abstract

As essentially the most downloaded singing app of all time, Smule Inc. has been investing on Android to enhance the general audio high quality and, extra particularly, to scale back latency, i.e. permitting singers to listen to their voices within the headset as they carry out. The groups specialised in Audio and Video allotted a major a part of 2021 into making the required modifications to transform the Smule software utilized by over ten million Android customers from utilizing the OpenSL audio API to the Oboe audio library, enabling roughly a ten%+ enhance in recording completion charge.


Smule Inc. is a pacesetter in karaoke, with an app that helps thousands and thousands of individuals sing their favourite songs and share performances each day. The Smule software goes past conventional karaoke by specializing in co-creation, providing customers the distinctive alternative to share music and collaborate with associates, different singers on the platform, and their favourite music artists. Audio high quality is paramount, and, in 2020, the Smule workforce noticed potential to boost the expertise on Android.

Screenshots of Smule karaoke app

Smule’s legacy OpenSL implementation wasn’t well-suited to leverage the blazing-fast {hardware} of latest units whereas supporting the various units throughout its world-wide market. Smule’s improvement workforce decided that upgrading the audio system was a vital and a logical enchancment.

Oboe Rollout Technique

Smule was confronted with two attainable routes for enchancment: instantly focusing on AAudio, a high-performance Android C audio API launched in Android O designed for functions that require low latency, or Oboe, which wraps each AAudio and OpenSL internally. After cautious analysis, Smule’s improvement workforce opted for Oboe’s easy-to-use code base, and broad machine compatibility, and strong group assist, which achieved the bottom latency and made the perfect use of the obtainable native audio.

The conversion to Oboe represented a major architectural and technological evolution. In consequence, Smule approached the rollout course of conservatively, with a deliberate, gradual launch that began with a small number of machine fashions to d validate high quality. Week after week, the workforce enabled extra units (reverting a restricted variety of units exhibiting issues in Oboe again to OpenSL). This incremental, methodical strategy helped to reduce threat and allowed the engineering workforce to deal with device-specific points as they occurred.

Bettering the Audio High quality Expertise

Smule switched to Oboe to assist enhance the app expertise. They hoped to scale back dramatically audio playback crashes, get rid of points equivalent to echo and crackling throughout recording, and scale back audio latency. A latest article within the Android Builders weblog reveals that the common latency of the twenty hottest units decreased from 109 ms in 2017 to 39ms at present utilizing Oboe. Whereas a monitoring delay of 109ms is heard as a definite echo which interferes with dwell singing, 39ms is beneath the appropriate threshold for real-time functions. The latencies of prime units at present are all inside 22ms of each other, and this consistency is a giant plus.

The carry in recording completion charge Smule has seen utilizing Oboe is probably going as a consequence of this decrease latency, permitting singers to listen to their voices within the headset as they carry out with Smule’s world-class audio results utilized, however with out an echo.

Utilizing an efficient collaborative GitHub portal devoted to Oboe, the Google workforce performed a major function in Smule’s Oboe integration, offering them with key insights and assist. Working collectively, the 2 groups have been in a position to launch the most important Oboe deployment so far, reaching thousands and thousands of lively customers. The Smule workforce contributed to addressing some Oboe code points, and the Google workforce coordinated with sure cellular machine makers to additional enhance Oboe’s compatibility.

Audio high quality is of the utmost significance to our group of singers, and we’re grateful for our shared dedication to delivering the absolute best expertise in addition to empowering musical creation on Smule. – Eric Dumas, Smule CTO.

Given the huge scale of the operation, it was solely pure to face device-specific points. One notable instance was an OS built-in performance that injected echo sound results within the uncooked audio stream, which prevented Smule from accurately making use of its personal patented DSP algorithms and audio filters. Google’s workforce got here to the rescue, offering lightning quick updates and patches to the library. The method of reporting Oboe points was simple, effectively outlined, and dealt with in a well timed method by the Google workforce.

Smule overcame different device-specific roadblocks collectively, together with errors with particular chipsets. For example, when Oboe was asking for mono microphone enter, a couple of units offered stereo inputs combined into one pretend mono microphone enter. Smule created a ticket in Oboe’s GitHub, offering examples and reproducing the difficulty utilizing the Oboe tester app.

The Google-developed Oboe tester app was a useful software in fixing and figuring out points all through the implementation. It proved particularly helpful in testing most of the options of Oboe, AAudio, and OpenSL ES, in addition to testing Android units, measuring latency and glitches, and way more. The appliance affords a myriad of options that may assist to simulate nearly any audio setup. The Oboe tester can be utilized in automation testing, by launching it from a shell script utilizing an Android Intent. Smule relied closely on the automation testing, given the massive variety of units coated within the integration.

As soon as Smule was assured the device-specific points have been resolved and the Oboe audio was steady sufficient, Smule switched to a wider cut up testing rollout strategy. In only a few weeks, Smule elevated the inhabitants utilizing Oboe from 10% to 100% % of the profitable units, which was solely attainable because of the optimistic suggestions and inexperienced KPI metrics Oboe acquired repeatedly all through the discharge journey.

The outcomes converse for themselves. Smule customers on Oboe are singing extra – it’s so simple as that. Distinctive karaoke recordings and efficiency joins, or duets, elevated by a whopping 8.07%, Distinctive uploads by 3.84%, and music performances have been accomplished by 4.10% extra. Smule has noticed in Q3 and This fall 2021 a rise of the recording completion charge by 10%+.

Utilizing the Firebase Crashlytics software by Google, Smule has seen a decline in audio-related crashes for the reason that full Oboe launch, making the app extra steady – even on lower-end units. Smule’s devoted buyer assist workforce was thrilled to report a 33% discount in audio-related complaints, together with points like (unintended) robotic voice and echo.

The choice to modify to Oboe has paid off in spades. The appliance is functioning higher than ever and Smule is well-equipped to face additional developments in audio and {hardware} with the up to date know-how. Most significantly, Smule customers are pleased and making music, which is what it’s all about.



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