The symptom that points here
This article is about one specific pattern: some channels have sound and others are silent, with the picture fine throughout.
If everything is silent, the cause is more ordinary — volume, mute, the wrong output selected — and our guide to audio and subtitle problems covers that along with out-of-sync audio. Come back here when it is channel-specific.
Why audio formats differ between channels
Channels choose their own audio encoding, and the common ones are not equally supported everywhere.
- AAC — widely used and supported almost universally.
- MP2 — older, common on European broadcast feeds, generally well supported.
- AC3, also called Dolby Digital — standard for surround sound. This is where problems start, because decoding it requires a licence and not every device includes one.
- E-AC3, or Dolby Digital Plus — newer, and less widely supported again.
So a stick that plays AAC channels perfectly may be silent on an AC3 one, purely because it cannot decode that format.
What passthrough actually does
Two ways audio can reach your speakers.
Decoded by the device. Your streaming box turns the audio into ordinary sound and sends that out. Requires the device to understand the format.
Passthrough. The device sends the compressed audio onward untouched and lets a soundbar or receiver decode it. Requires the receiving equipment to understand the format.
Passthrough is what surround sound needs, since only a receiver can do anything useful with multichannel audio. But it moves the requirement downstream — enable it and send AC3 to a soundbar that cannot decode AC3, and you get silence.
That is the single most common cause of channel-specific silence in a setup with separate audio equipment.
Working out which end is failing
A quick test isolates it.
Play the silent channel with the television's own speakers, bypassing the soundbar. If sound appears, the television could decode it and the soundbar could not — the problem is downstream, and passthrough is the setting to change. If it is still silent, the device or television cannot decode the format itself.
A second test: play the same channel on a phone. Phones handle AAC and AC3 widely. Sound on the phone confirms the audio track is present and the problem is entirely at the television end.
The settings to change
In the player
Look for an audio output or passthrough option. Where a player offers a choice between automatic, PCM and passthrough, PCM is the safe setting: it forces the device to decode and send ordinary stereo, which almost anything can play. You lose surround sound and gain reliability.
On the television
Under sound or audio output there is usually a digital output format setting, offering something like auto, bitstream or PCM. Bitstream is passthrough. Setting it to PCM has the same effect as above.
On the soundbar or receiver
Check what formats it lists as supported. Older units often handle AC3 but not E-AC3, which produces silence on exactly the newer channels.
The trade-off
Forcing PCM is the reliable answer and it costs you surround sound — everything becomes stereo. For live television that is a small loss, since most channels are broadcast in stereo anyway.
If surround matters for films, one workable approach is to leave passthrough on and switch to PCM only for the channels that are silent, where your player supports per-channel audio settings. Otherwise choose the setting that matches most of your viewing.
When it is not the format
- A channel with multiple audio tracks may default to one you cannot hear or do not want. Cycling audio tracks is covered in audio and subtitle problems.
- HDMI-CEC volume confusion, where the television thinks the soundbar has the volume and the soundbar thinks the television does.
- A genuinely silent broadcast, which happens occasionally and affects everyone watching.
Frequently asked questions
Why do some IPTV channels have no sound?
Usually because they use an audio format your device or soundbar cannot decode, most often AC3 or E-AC3. Channels using AAC play fine, which is why the problem looks selective.
What is audio passthrough?
Sending compressed audio onward untouched so a soundbar or receiver decodes it rather than your streaming device. It is needed for surround sound, but it means the receiving equipment must support the format.
Should I use PCM or bitstream?
PCM is the reliable choice: the device decodes everything and sends ordinary stereo, which almost anything can play. Bitstream, meaning passthrough, gives surround sound but requires downstream support.
My soundbar is silent but the TV speakers work. Why?
The television could decode the format and the soundbar could not. Switching the digital audio output from bitstream to PCM usually resolves it, at the cost of surround sound.