BBC HD Channels: quieter audio?

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mooblie
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I have (finally) entered the world of HD broadcast.  I have a new Sony set with integrated FreeviewHD.  When switching between BBC One (SD) and BBC One HD, there is clearly a shift in broadcast audio levels.  Naturally, the downstream audio chain from my TV is identical in both cases (= optical TOS-link to a AV Receiver).
 
The HD channel audio is almost exactly 6dB down on the SD channel.  With the AV Receiver's digital volume level readout, it's relatively easy to measure this difference.
 
Is this normal?  Is it me?  It this by design? If so, why?  Is the HD camp at the BBC afflicted by the "Radio 3" syndrome? - wanting more headroom than the rest of the broadcast universe?
 
Any comments?

Martin - DVdoctor in moderation. Everyone is entitled to my opinion.

Gavin Gration
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Re: BBC HD Channels: quieter audio?
We have Freesat HD (external BDR/HDD unit) & Freeview (built in) - the audio levels are all over the place from channel to channel - commercial channels pump the ads (of course).
 
I just accept it. 
Bob Aldis
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Re: BBC HD Channels: quieter audio?
BBC are also putting out a lot of there HD stuff in surround sound which on my AV amp tends to need more volume.
 

Bob Aldis

MAGLINK
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Re: BBC HD Channels: quieter audio?
The HD channels tend to have 5.1 dolby surround encoding most of the time and the levels are different to normal broadcast as the 5.1 is mixed down to Lt Rt.
mooblie
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Re: BBC HD Channels: quieter audio?
OK, thanks, guys.  Maybe I'd better try experimenting with my AV receiver's options for decoding the TOS-link optical audio signal into different formats...

Martin - DVdoctor in moderation. Everyone is entitled to my opinion.

Alan Roberts
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Re: BBC HD Channels: quieter audio?
Levels are the same for me, I ignore the surround sound (haven't got space for the speakers, or the courage to try to get Claire to accept the idea) by setting the TV to deliver stereo.

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mooblie
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Re: BBC HD Channels: quieter audio?
Thanks Alan, that was the prompt I needed: the TV audio settings.  
 
When I switched the TV Digital Audio Out from "Auto" to "PCM" (the only two choices!) the levels now seem more consistent between SD/HD channels.  Thanks again.
 
( I guess "Auto" and "PCM" may be SonySpeak for "Surround" and "Stereo"? )

Martin - DVdoctor in moderation. Everyone is entitled to my opinion.