OK never mind - ... maybe what I said is so blindingly obvious
bbc freeview mux are broadcast with several audio streams 2.0 aac and sometimes a 5.1, nowtv streamed is just 2.0
when they prepare the 2.0 track they mix down the original 5.1, from a movie say, as you can do on a pc with ffmpeg command line example I showed
they can mix the lfe track into the 2.0, in the same way that your own av can.
since the lfe may be in the 2.0, it can be delievered to your stereo amp, which refutes the point hornetstinger had made
I'm sorry to say
@jpaul, but your recent posts in this thread read to me largely as mad rambling. They seem to lack structure, and appear to be a sort of stream-of-consciousness outpouring of disjointed thoughts. Maybe what's in your head makes sense, but once it reaches the written page, it's not so clear. I'm trying to pick through the bones of them to make some sense, but it's not that easy. Perhaps you should proof-read and edit?
The thread is about the pros and cons of a stereo amp versus an AV receiver. The speaker package will be run as 2.1 from the stereo amp because it has a sub out. However, this isn't the same kind of sub out as an AV receiver. It isn't managed in the same way. There's no crossover setting in the amp. The sub gets a full range audio signal.
Full range for stereo equipment usually means 20Hz-20kHz. The sub's own volume, phase and crossover controls will blend the sub with the main speakers.
One of the intended sources is a 4K player of some description. It's reasonable to presume then that the source is capable of delivering a 5.1 audio signal. From that,
@hornetstinger made the valid point that when using a stereo amp would lose the .1 lfe content.
Strictly speaking, the stereo amp wouldn't lose the signal as such because that would imply that it has received it in the first place, and that would be wrong. The .1 lfe would be discarded before it reaches the amp in the process of down-mixing a multichannel signal to stereo ready to be fed to a stereo amp.
You're trying to argue that it wouldn't be discarded.
It appears from what you've written that you seem to think that the way an AV receiver works with a 2.1 speaker package then somehow dictates how a stereo amp with a sub out socket should work. The way your posts read, you seem to be confusing the bass management of a stereo source signal with how lfe is handled.
What happens with the bass from a 20Hz-20kHz main channel signal (a 2.0 signal, if you will), and how it is divided between the main speaker and the sub is nothing to do with lfe. There is no lfe content in a 2.0 source signal. The fact that a sub gets some bass signal fr4om an AV receiver doesn't mean that its an lfe signal. It's just bass. It's whatever is below the crossover-point set in the AV receiver's bass management controls.
The fact that you can use some PC software to downmix a signal doesn't prove anything. By the way, your command line only appears to list the main surround channels. There's no part that appears to deal with lfe. Oopsie
You've then banged on about broadcast audio streams - which I guess relative to you using the ffmpeg sofware.
Freeview doesn't broadcast with a 5.1 and a 2.0 audio stream at the same time. It's wasteful of data bandwidth. There's no point either. Where the source film or TV program is in true 5.1 surround, but the TV or audio device requires a stereo signal, then it's the receiving device that is responsible for creating a stereo signal. It does this by using the 5.1 donor signal. In the process, anything in the .1 lfe channel is discarded.
For a movie or TV program that was filmed and edited to be in stereo, then the broadcaster still uses the 5.1 framework, but only populates the channels relating to FL and FR. This means that centre, surround left, surround right and the lfe channels are empty of content. It's true then to say that the BBC has programming in 2.0 or 5.1, but a HD programme with 5.1 audio doesn't also have a 2.0 downmix broadcast at the same time. This goes some way to explaining why some people report incorrect audio flagging. The program is in stereo (usually with Dolby surround) but the receiving equipment reports it Dolby Digital after being transcoded from AAC-LE.
