This issue occurs due to incompatibility between the computer’s video playback software and the audio encoding format used by the Xiaomi Smart Camera C500. When the videos are played on the phone through the Xiaomi Home App, the built-in player can decode both video and audio correctly.
However, some computer players can not fully support the same audio codec, which results in silent playback. To resolve this, try switching to a different video player on your computer, such as VLC Media Player or PotPlayer, which support a wider range of codecs. Updating the current player or installing additional codec packs can also help restore normal sound playback.