Efficient Data Compression for Vocal Recordings

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More people and businesses are experimenting with audio recordings for communication instead of phone calls and email. Email and messaging services like WhatsApp and iMessage allow users to send large attachments to clients, coworkers, and friends. File sizes can swell for audio recordings over thirty minutes, making it a challenge to send and receive audio messages easily.

In this post, we’ll specifically address how to optimize audio files intended for use communicating back and forth between individuals and small groups. This is for recordings that aren’t intended for archival storage, nor mass communication, but instead prioritize convenience, clarity and intelligibility. 

The biggest challenge is to keep the file sizes small enough to send through common file transfer services. Most email services, like Gmail, limit file attachments to 25MB, making it difficult to send longer audio recordings without proper data compression. Though Google integrates its Google Drive service into Gmail for larger attachments, exceeding the total allotted 15GB storage per user can result in additional storage fees. It makes sense to keep file sizes small to avoid using storage unnecessarily.

At the time of writing, iMessage has an impressive 100MB attachment limit, whereas WhatsApp surpasses this with a 128MB limit. Even with the larger file attachment sizes, sending voice recordings from a mobile device over 4G cellular networks can be slow and unreliable. In these cases, smaller file sizes can keep your workflow mobile and efficient. 

Apps like Voice Memos in Apple iOS  optimize data compression for vocal recording automatically. To share a file from the app, simply click the three dots next to the recording, then tap “Share” to see options to send the file via email, AirDrop, iMessage, or other app. By default, the file will be encoded into a variable bit rate AAC file somewhere around 64kpbs, which is perfect for high quality voice recordings. 

When recording on a laptop or desktop, however, a few additional steps are often required to optimize recordings for convenient file transfer and playback. We recommend starting with a high-quality file, then converting it a much smaller file. This can be accomplished most easily using the Finder in MacOS, and we’ll include steps for using doing so on Adobe Media Encoder as well. 

File Encoding in MacOS

Start with a high-quality audio recording, preferably one that was either recorded in a DAW, editing software, or imported from a portable recorder. If possible, keep your original file as a lossless WAV, AIFF, ALAC, or a high-quality AAC file (128kbps or greater). MP3 files, 128kpbs or higher are also acceptable. 

MacOS:

In the MacOS Finder, right-click the audio file and select “Encode Audio Files”. This option will be available for all common audio file formats. 

Set the encoder quality to “Spoken Podcast”. Do not delete the source files unless desired. 

Once complete, you’ll have a compressed file designed for sending easily over the web, and will play on virtually every software or playback device. 

Adobe Media Encoder:

We created a preset for you to easily download and load into your Adobe Media Encoder presets. We included step-by-step instructions on how to configure these settings below.

Voice and Podcast Adobe Media Encorder Preset – Click to Download

Import your high-quality audio file into Adobe Media Encoder, then select AAC under “Format”.

Next, click the preset to make custom settings adjustments

Select the “Audio” category, and under “Basic Audio Settings”, set channels to “Mono”. This configures the file to play with equal loudness in both speakers for stereo. 

Change the audio codec to AAC+ Version 2. This uses the most recent version of this audio codec for improved performance with fewer compression artifacts.

Next,  click the bitrate drop down and set the bitrate to 40kbps. This is the perfect compromise between size and audio quality for vocal audio.

Verify that these setting match, then click okay to confirm the changes and return to the main screen.

Click the play icon to begin rendering the file.

Once complete, you can store the preset for the future and process audio files quickly in large batches. When the additional space is critical, such as for email, lowering the bitrate to 20kpbs will suffice, albeit with slightly more noticeable data compression artifacts.

If you found this helpful or have any questions, leave us a comment below.

CEO and Founder of Finewav. Instagram: @ErykThompson Vero: @ErykThompson

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