![]() ![]() Audio quality sensitivity depends on each listener’s attention to audio details and the quality of the playback speaker (e.g. From our previous experiments on visual quality, we knew that quality of experience is subjective and unique to content type and community type. To find the strongest signal on Instagram listeners’ preferences for audio quality, we considered ways to focus our audio quality improvements. Content and Community Specific Quality Preferences In our experiment, we aimed to make the right quality tradeoff for the right content. Increasing this bitrate for all content is particularly risky, since we know that most content has simple audio and will not benefit from the audio side of the tradeoff. While we can increase the audio bitrate, we must weigh the tradeoffs between audio quality and video quality. In these situations, a difference of 64kbps can be substantial in the playback experience. However, in low bandwidth situations we serve video at much lower bitrates. High quality video has a bitrate so high that the difference between 64kbps and 128kbps audio has a negligible impact on playback rebuffers. We need to split bandwidth between audio and video because of limited overall bandwidth, so this is a zero-sum game. We unfortunately can’t simply increase bitrate for all content. For example, in Instagram’s Music Sticker Stories, we noticed that the compressed audio for snare drums, cymbals, voice, and reverb sounded drier and thinner than they did in the original recordings. When we tested the Instagram app, we observed common compression artifacts. We received reports that Instagram’s audio sounded “blown out” or too low quality for artists to want to share certain songs on Instagram. music recordings), it became clear that 64kbps was not sufficient for delivering high quality audio. However, as Instagram creators started posting studio-produced audio content (e.g. The microphone on a phone doesn’t produce a rich audio signal, so despite the low bitrate, Instagram’s audio compression performed well for most content. Prior to our audio quality improvement efforts, Instagram’s default bitrate for audio in videos was 64kbps. Since we kept the audio codec and sample rate constant, and bitrate was simple to change, we chose to vary the bitrate in our audio quality improvement experiment. When the bitrate is too low, the encoder removes audio details that it considers less important. This allows the compressed audio encoding to retain more features of the original audio file with fewer compression artifacts. In other words, a higher bitrate means more data and less compression in the audio encoding. Bitrate, measured as kilobits per second (kbps), varies linearly with the number of bits in the audio file. The Nyquist-Shannon Sampling Theorem says that: “A band limited continuous-time signal can be sampled and perfectly reconstructed from its samples if the waveform is sampled over twice as fast as its highest frequency component.” Instagram uses an industry standard 44.1kHz sample rate, more than enough to convey the 20kHz max that most people can hear, so we ruled out sample rate as a variable worth changing. Sample rate affects the upper bound of frequencies that our audio encodings can represent correctly. ![]() Changing the audio codec was not the simplest solution, so we decided to keep AAC as our audio codec selection for our audio quality improvement experiment. Instead of potentially focusing plenty of engineering time to build an audio quality metric, we pursued the simple solution first and aimed to demonstrate that Instagram listeners cared about audio quality via existing engagement metrics. #Mp3 gain good level 2019 install#With the scale and range of Instagram’s content, it’s important to rigorously evaluate which codecs best fit the content and install metrics to track audio quality. Different audio codecs have different levels of lossy compression, and they perform differently on different types of content. The audio codec selection, sample rate, and bitrate all contribute to the quality of the audio encoding. Instagram’s video system has access to multiple levers that affect audio quality. These differences collectively lower the audio quality perceived by listeners. Some examples of compression artifacts are reduced clarity in high frequency sounds, weaker bass, and noise. However, in exchange for smoother playback, this introduces the risk of compression artifacts. Instagram delivers compressed audio to enable smooth video playback with fewer stalls caused by rebuffers. Instagram’s Music Sticker song suggestions for the pop music genre What is Audio Quality?Īudio quality is a measure of how closely the audio we deliver to Instagram apps matches the original uncompressed audio file. ![]()
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