Find where the sound stops

Start with the playback and TV controls

1. Make sure the file is playing rather than paused or still preparing.
2. Check mute and volume in the page’s playback controls.
3. Check the TV’s own volume, mute state and selected audio output.
4. For manual phone mirroring, confirm that the system connection is active, then return to the visible player and press Play.

The website cannot inspect the volume of every TV, soundbar or system mirroring destination. In manual modes it cannot even confirm which TV is connected. The local player advancing therefore does not, by itself, prove that audio reached the television.

Choose the intended audio track

Open the gear-shaped Settings button and inspect Audio. A film may contain another language, a commentary track or more than one sound format. Choose the intended track and let the updated preparation finish before judging the result.

If one track works and another does not, note their formats rather than repeatedly reconnecting the same silent selection. The app does not invent an audio track when the file contains none. For standalone music, see casting audio files; for mixed video and sound tracks, use the MKV guide or MP4/MOV guide.

Understand container and sound formats

MKV or MP4 describes a container, not its sound codec. The browser can keep compatible video compressed while converting AC-3, E-AC-3 or DTS sound to stereo AAC. That preparation is not a promise of original multichannel or surround passthrough.

Other tracks depend on the available browser decoders and encoders. A format needing whole-file FFmpeg conversion has a separate 256 MiB input/output bound. A large file using an unsupported conversion path may therefore fail even though other multi-GB films stream successfully. Google documents different media capabilities across Cast devices; an accepted extension is not a guarantee for every combination.

Treat phone screen mirroring as its own audio path

In Android manual mode, Android captures the local player. Audio capture depends on the producing app’s native usage and capture policy; website JavaScript cannot override that policy. Android’s playback-capture documentation explains those restrictions. Do not grant unrelated microphone or location permissions as a blanket fix for this route.

On iPhone, use an AirPlay-compatible TV and the system’s Screen Mirroring selection, then return to Safari and tap Play on this iPhone. Follow Apple’s mirroring instructions. A Cast-only TV cannot use this mode, and successful local video preparation does not verify AirPlay sound.

Make the next comparison useful

Try a short, familiar file with a supported audio track. Compare local phone playback with the TV output when using a manual route. If the local player is silent too, investigate the track or preparation first. If local sound works but the TV is silent, investigate the mirroring destination and TV output.

Keep the phone visible and unlocked, and the computer awake. Note whether sound fails immediately, after a seek or after switching apps. A short comparison with known sound can help narrow the problem, but check the actual TV output before starting a longer film. For interruptions affecting both picture and audio, continue with quality and buffering checks.