Mp4a.40.2 -140-

| Format ID | Codec String | Bitrate | Sample Rate | Channels | | :--- | :--- | :--- | :--- | :--- | | | mp4a.40.2 | 48 kbps | 22.05 kHz | Mono/Stereo | | 140 | mp4a.40.2 | 128 kbps | 44.1 kHz | Stereo | | 141 | mp4a.40.5 (HE-AAC) | 256 kbps | 48 kHz | Stereo |

Thus, the string mp4a.40.2 -140- literally reads as: "MPEG-4 AAC-LC audio, presented in the format profile #140." mp4a.40.2 -140-

When logged as mp4a.40.2 -140- , the hyphens indicate: | Format ID | Codec String | Bitrate

AAC comes in various flavors, such as AAC-Main, AAC-SSR (Scalable Sampling Rate), and AAC-LD (Low Delay). AAC-LC is the "Goldilocks" profile. It provides high-quality audio at lower bitrates (like 128kbps or 192kbps) without the high computational demands of the "Main" profile. Because it strikes the perfect balance between file size, quality, and processing power, AAC-LC is the standard for Apple’s iTunes Store, YouTube, and most streaming services. Because it strikes the perfect balance between file

In the modern digital landscape, the way we consume sound is governed by invisible sets of instructions known as codecs. Among these, , the technical identifier for AAC-LC, stands as a cornerstone of the internet’s auditory infrastructure. Though it remains hidden from the average user behind the simple extension ".m4a" or within an MP4 video file, this codec is responsible for the clarity of our streaming music, the crispness of video calls, and the efficiency of global media distribution. The Efficiency of Compression