For 3G2 files, audio poses the biggest problem because they usually use the AMR voice codec, a format built for early cellular networks rather than long-term media use, relying on heavy compression that keeps only voice-range frequencies to travel over unreliable 2G/3G connections, making it fine for speech but not for modern playback; once faster networks and improved codecs like AAC and Opus became standard, AMR’s relevance faded, and many systems removed support due to telecom-specific standards and licensing, leaving many 3G2 files silent or unplayable today.

Video streams in 3G2 files often decode without issue since codecs such as legacy video formats contributed to modern standards and still have active decoders, but AMR wasn’t adopted into consumer media pipelines and relies on timing and encoding assumptions at odds with current audio frameworks, which is why playback often shows video without sound. During conversion of a 3G2 file into MP4 or another modern format, the AMR audio track is usually replaced with AAC or a comparable contemporary codec, fixing playback issues by using audio that modern tools fully support, so the result isn’t a repair of the old file but a translation into a more universal format, which is why conversion reliably restores audio and simple renaming fails to address the codec. In essence, audio failures in 3G2 files do not indicate lost data but highlight how tightly AMR was built around old mobile communication needs, and once that period ended, its support vanished, leaving otherwise complete videos silent unless converted.

You can determine whether a 3G2 file contains AMR audio by inspecting its stream metadata rather than depending on playback results, using a media analysis tool that identifies each audio and video track, and if the audio track appears as AMR, AMR-NB, or AMR-WB, then the file uses Adaptive Multi-Rate, which often leads to missing audio on newer players; viewing detailed codec info in a player like VLC allows you to check the audio section directly, and if VLC shows AMR but other players stay silent, that contrast confirms AMR is behind the issue.

Another way to confirm AMR audio is by trying to import the 3G2 file into a modern video editor, where many editors will either reject the file outright or import only the video while ignoring the audio, often showing an error about an unsupported codec, which, while less explicit than a metadata tool, strongly suggests the audio is not AAC or another common format and that AMR is likely; you can also verify this by converting the file, since most converters display the source codec before transcoding, and if AMR appears as the input and AAC as the output—or if no audio shows up unless conversion is forced—it confirms that AMR was the original encoding and is unsupported by default.