They don't have to. The BBC transmit a stereo sound track on audio PID 5402. You can infact select it by pressing the speaker button on the Humax HDR remote and selecting the 'Audio Description' soundtrack as opposed to the 'English' soundtrack.

ITV HD has an even more meaningless name for the stereo soundtrack. The name is: 'und'.

So why do Humax describe the fix in the new beta firmware as "down-mixing"? Are you saying they could have done it a better way?

Which means if you have a AV amplifier without a AC3 decoder connected by s/pdif to a hdr you are forced to listen to the audio description if you want to listen to the BBC-HD channels.

Discovered downmix to lpcm over s/pdif does work. After changing the menu option you simply have to retune to a channel with ac3 sound. The option takes effect when tuning to a channel transmitting ac3

I this related to the problem I discovered recently when I, for the first time, transferred an HD recording from the Humax to my PC?

When I tested it I discovered that the sound track was the 'audio described' version and there was no way to select an alternative track.

Is this muppetry the fault of Humax of the BBC?

Depends on your point of view, The BBC for not providing a lpcm track free from Audio Description or in this case the failure of whichever way you played back the recording on your PC to select the ac3 audio track rather than the lpcm one both of which will be present on the recording.

vlc player on my laptop PC plays back unencrypted HD no problem downmixing to stereo using the PC speakers and outputting AC3 over hdmi to my amplifier.

On thing I have yet to try is to see if turning off DD causes the audio track recorded to be downmixed as well as the output.

Postscript, Humax have got it right. The ac3 track is recorded as is, whether downmix is on or off. Replay is DD5.1 with DD on and lpcm stereo with it off.

It was VLC I used to play back the recording.

It's one of those annoying programs that seems to have upwards of a million options but never the one you actually want.

There may be a way to select a different audio track but I haven't found it.

Where do you find this menu option?

Menu/Settings/TV setup Dolby Digital On/Off

Have you tried this on a recording or just on live TV?

See post #30 ^^^

On the tool bar Audio/Audio Track, mine always defaults to the
AC3 track.

Also try Splash-Lite (it's free and uses less resources than vlc so will play HD on a less well specified PC)

http://mirillis.com/en/

Are you able to set this to Off and then switch between BBC HD, BBC One HD and ITV1 HD, avoiding 5.1 sound each time? (I find ITV1 HD defaults to 5.1)

They all do except there's no 5.1 on ITV1-HD it's only DD2.0 and only on London ITV1-HD. The option uses the 5.1 track and dowmmixes this to lpcm prologic 11 stereo surround when Dolby Digital is set to off. Once you turn it off the next time you view a HD channel or recording the box outputs lpcm stereo from it's s/pdif using a DD2.0 or DD5.1 track (I presume hdmi audio is the same)

For reference ITV1-HD Granada is 1920 x 1080 but only lpcm stereo (MP2 transmitted), ITV1-HD London is 1440 x 1080 and DD2.0 audio

I too can confirm that this works.

Also have found that the difference in volume between SD and HD channels when connected by HDMI to a Panasonic TV has been resolved. Has anyone else noticed this and explain why?

Yes because the box is downmixing to lpcm stereo rather than the TV. Thanks for the post I could not test the hdmi output because of the physical seperation between the hdr/tv and the AV amp.

Further information, changing the menu option does not change the volume levels so perhaps the the box is always downmixing to lpcm when connected to the TV via HDMI?

Did you retune to a HD channel after changing the option. If you are on a HD channel when you make the switch it only works after going to a different channel and back again.

I earlier tried surround sound down-mixing on a BBC HD live broadcast and for the life of me cannot get it to work. It stays as DD5.1.

Strange, is the sound over hdmi or s/pdif and did you tune off BBC-HD and back again ?

Ah! Tuning off and on is not something I tried (over SPDIF).

Ok. Got it working now. And more importantly for me turning down-mixing back off works too.

Fooled me the first time I tried it , you expect the menu switch to take effect as you change the setting and naturally tune to a AC3 channel to check as you make the setting change.

Have you tried that test of recording with down-mixing turned on to see what happens to the saved audio?

Have you?

If that refers to me yes . See post 30. The saved audio is what you would expect a straight copy of the original audio streams, conversion to lpcm stereo for AC3 streams is on replay with DD set to off. In other words existing recordings replayed to a AV system without AC3 decoding will now replay OK.