Dolby Pro Logic
 

I've just upgraded from a non-HDMI AV amp to an HDMI one, the main input
is my mythTV PC via HDMI (still using audio over SPDIF temporarily) ...
it's nice to have switching on the TV automatically power up the amp
too, and the TV's remote control the amp's volume and input selection.

I have the amp's surround mode set to "auto".

When watching a normal programme (i.e. not a film) the amp correctly
selects Stereo.

When watching something with 5.1 audio (e.g. a film from a freesat HD
channel) the amp automatically selects Dolby Digital and is in full 5.1 mode

When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the channels.
If the encoding is there, why can't the amp detect it and automatically
enable it?

Or am I fooling myself on material that doesn't have any encoding, and
I'm just hearing a synthetic surround effect?

How much freeview/freesat material does have Pro Logic encoding?

Dolby Pro Logic
 

Andy Burns wrote:
When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the channels.
If the encoding is there, why can't the amp detect it and automatically
enable it?

Maybe I'm missing something here, but I don't think that any Freesat SD
channels carry Dolby Digital audio.

Dolby Pro Logic
 

John Legon wrote:

Maybe I'm missing something here, but I don't think that any Freesat SD
channels carry Dolby Digital audio.

No, I'm not expecting them to have Dolby Digital, but do they carry
Dolby Pro Logic encoded in their stereo?

I thought (at least some) films did, should a decoder normally switch
automatically if the encoding was there?

Dolby Pro Logic
 

John Legon wrote:
Andy Burns wrote:
When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the channels.
If the encoding is there, why can't the amp detect it and
automatically enable it?

Maybe I'm missing something here, but I don't think that any Freesat SD
channels carry Dolby Digital audio.

No not 5.1 audio, but Pro Logic audio should make its way through the system,
as long as the MPEG coding is transparent enough. In reality I think if the
audio is anything less than 256kb/s it won't work ?

--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

Dolby Pro Logic
 

"Andy Burns" wrote in message
o.uk...

Or am I fooling myself on material that doesn't have any encoding, and
I'm just hearing a synthetic surround effect?

How much freeview/freesat material does have Pro Logic encoding?

My AV amp is handling all stereo in PL II mode and at times BBC1 HD or BBC
HD have a DD sound it changes automatically to DD.
My understanding of PL decoding is that it takes the mono content of the L
and R stereo and puts it through the centre speaker.
IF the program does have surround, such as a movie might have, that will go
to the rear speakers.

I would suggest you set your amp to PL and see if on BBC HD versions see if
some programs change automatically to DD as mine does.

Regards
David

Dolby Pro Logic
 

In article ,
Andy Burns wrote:

I've just upgraded from a non-HDMI AV amp to an HDMI one, the main input
is my mythTV PC via HDMI (still using audio over SPDIF temporarily) ...
it's nice to have switching on the TV automatically power up the amp
too, and the TV's remote control the amp's volume and input selection.

I have the amp's surround mode set to "auto".

When watching a normal programme (i.e. not a film) the amp correctly
selects Stereo.

When watching something with 5.1 audio (e.g. a film from a freesat HD
channel) the amp automatically selects Dolby Digital and is in full 5.1 mode

When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the channels.
If the encoding is there, why can't the amp detect it and automatically
enable it?

Or am I fooling myself on material that doesn't have any encoding, and
I'm just hearing a synthetic surround effect?

How much freeview/freesat material does have Pro Logic encoding?

Dolby Stereo soundtracks are technically speaking just two-channel
stereo. There is no way of identifying from the soundtrack the fact that
it is in Dolby Stereo, and Freeview doesn't carry any flag to identify
this.

In Dolby Stereo, the centre channel is reduced in level by 3dB and
placed equally in left and right. The single rear channel is
phase-reversed, Dolby B encoded, and added to the left and right.
(Therefore if you listen in mono the rear channel disappears). On
playback a logic steering system recognizes the four channels and
sort-of separates them (there is a good deal of leakage). At its very
simplest:

Sound in L only appears in the left channel.
Sound in R only appears in the right channel.
Sound which is the same in L & R is placed in the centre channel and
muted in the left and right channels.
Sound which is the same in L & R but out of phase is placed in the rear
channel and muted in the other three.

Modern decoders can be quite sophisticated in steering the sound to
provide a convincing soundstage, though they can't position discrete
sounds in the rear in the way that Dolby Digital can.

You will always have to switch Dolby Digital decoding on manually.

Dolby Pro Logic
 

Mark Carver wrote:
John Legon wrote:
Andy Burns wrote:
When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the
channels. If the encoding is there, why can't the amp detect it and
automatically enable it?

Maybe I'm missing something here, but I don't think that any Freesat
SD channels carry Dolby Digital audio.

No not 5.1 audio, but Pro Logic audio should make its way through the
system, as long as the MPEG coding is transparent enough. In reality I
think if the audio is anything less than 256kb/s it won't work ?

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.

Dolby Pro Logic
 

Roger Wilmut wrote:

Dolby Stereo soundtracks are technically speaking just two-channel
stereo. [] the centre channel is reduced in level by 3dB and placed
equally in left and right. The single rear channel is phase-reversed,
Dolby B encoded, and added to the left and right. [] On playback a logic
steering system recognizes the four channels and sort-of separates
them

Thanks Roger, I was aware that it's just a stereo signal, rather than 6
discrete channels, and that it used phasing/matrixing to do the L/R/C/S
steering.

You will always have to switch Dolby Digital decoding on manually.

I presume you mean Pro Logic rather than Digital there? Seems a shame
there's no way to automatically detect it, but thanks for confirming.

Dolby Pro Logic
 

"Roger Wilmut" wrote in message
...



You will always have to switch Dolby Digital decoding on manually.

Seems to be only at times and on HD from the BBC as far as I have
experienced, so how would a person who's equipment that is not automatic
know to do it manually?
Regards
David

Dolby Pro Logic
 

In article ,
Andy Burns wrote:
No, I'm not expecting them to have Dolby Digital, but do they carry
Dolby Pro Logic encoded in their stereo?

Any stereo signal can carry pro logic - that's the point of it. But how
much is made in that these days I don't know.

--
*Who are these kids and why are they calling me Mom?

Dave Plowman London SW
To e-mail, change noise into sound.

Dolby Pro Logic
 

John Legon wrote:

No not 5.1 audio, but Pro Logic audio should make its way through the
system, as long as the MPEG coding is transparent enough. In reality I
think if the audio is anything less than 256kb/s it won't work ?

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.

That's about right in my experience.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

Dolby Pro Logic
 

"Andy Burns" wrote in message
o.uk...
I've just upgraded from a non-HDMI AV amp to an HDMI one, the main input
is my mythTV PC via HDMI (still using audio over SPDIF temporarily) ...
it's nice to have switching on the TV automatically power up the amp too,
and the TV's remote control the amp's volume and input selection.

I have the amp's surround mode set to "auto".

When watching a normal programme (i.e. not a film) the amp correctly
selects Stereo.

When watching something with 5.1 audio (e.g. a film from a freesat HD
channel) the amp automatically selects Dolby Digital and is in full 5.1
mode

When watching a film (from a freesat or freeview SD channel) it never
seems to automatically choose Pro Logic, if I force the setting, the
decoding seems to work, I can hear the 'steering' around the channels. If
the encoding is there, why can't the amp detect it and automatically
enable it?

Or am I fooling myself on material that doesn't have any encoding, and I'm
just hearing a synthetic surround effect?

How much freeview/freesat material does have Pro Logic encoding?


Old analogue terrestial broadcasts with Nicam, used to carry Dolby Pro logic
quite well, so did analog satellite (but not as well).

BBC HD and BBC 1 HD regularly used Dolby Digital, although not always and
sometimes it will be partial (e.g. "[2/0]" so just stereo).

ITV HD uses Dolby Digital much less and to a first approximation I think
they CBA.

What I don't know without trying it out is whether Freeview or Freesat SD
carry surround sound signals or not. I suspect they probably don't because
of the extra bandwidth required.

Dolby Pro Logic
 

John Legon wrote:

Mark Carver wrote:

Pro Logic audio should make its way through the
system, as long as the MPEG coding is transparent enough. In reality I
think if the audio is anything less than 256kb/s it won't work ?

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.

I certainly heard surround from DareDevil[1] on Film4 last night, both
freeview and freesat, looking at the snippets I still have on disc, the
freesat signal was 192k MP2

Most of my freesat HD recordings seem to have AC3 2.0 rather than MP2
stereo (if they don't have AC3 5.1, that is) does that have better
bang-per-bit?

The audio bitrates on BBC1HD and BBCHD seem a mixed bag, some of the AC3
2.0 recordings are 384kbps, some of the AC3 5.1 are 256kbps, other BBC
recordings have 192kbps AC3 main audio with 256kbps MP2 audio description

I'll watch out for films on BBC channels to compare and contrast.



[1] I only watched it as a test, honest.

Dolby Pro Logic
 

"John Legon" wrote in message
o.uk...

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.


James Bond film Living Daylights is on now on ITV4 Freesat and AV Amp is PL
II and we are getting good cinema sound and yes surround as well.
Regards
David

Dolby Pro Logic
 

R. Mark Clayton wrote:

What I don't know without trying it out is whether Freeview or Freesat SD
carry surround sound signals or not. I suspect they probably don't because
of the extra bandwidth required.

My current understanding is as follows:-

*SD* services: Terrestrial and satellite use MPEG 1 Layer 2 audio. As stated
already Pro Logic tends to go through the system at the bitrates used by major
broadcasters, but it depends whether the programme has been encoded in that
manner or not.

For *HD* UK satellite, channels use AC-3, in either 2.0 or 5.1 formats, but
I'm told the pain of correctly managing the metadata in the playout systems
does mean other formats can and do leak out from time to time ?

For *HD* DTT it's currently use AAC-LC. again with either 2.0 or 5.1.

BBC and C4 are 5.1 capable. ITV doesn't currently use it. Dunno about C5 ?

In short if you want multi-channel sound then they're only available from HD
transmissions.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

Dolby Pro Logic
 

David wrote:
"John Legon" wrote in message
o.uk...

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.


James Bond film Living Daylights is on now on ITV4 Freesat and AV Amp is
PL II and we are getting good cinema sound and yes surround as well.
Regards

I've just checked and the audio bit-rate is 192 Kb/s, as it is also on
Film 4, so it seems that a rate of 256 kb/s isn't in fact necessary for
PL surround sound.

Dolby Pro Logic
 

John Legon wrote:
David wrote:
"John Legon" wrote in message
o.uk...

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.


James Bond film Living Daylights is on now on ITV4 Freesat and AV Amp
is PL II and we are getting good cinema sound and yes surround as well.
Regards

I've just checked and the audio bit-rate is 192 Kb/s, as it is also on
Film 4, so it seems that a rate of 256 kb/s isn't in fact necessary for
PL surround sound.

It's probably more of a Joint vs Discrete stereo thing ?

--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

Dolby Pro Logic
 

Mark Carver wrote:
John Legon wrote:
David wrote:
"John Legon" wrote in message
o.uk...

If that's the case, then you might hope to get surround sound with
movies shown on BBC 1, 2 & 4 but not on ITV 1 or Channel 4 & 5 ... SD,
based on current bit rates.


James Bond film Living Daylights is on now on ITV4 Freesat and AV Amp
is PL II and we are getting good cinema sound and yes surround as well.
Regards

I've just checked and the audio bit-rate is 192 Kb/s, as it is also on
Film 4, so it seems that a rate of 256 kb/s isn't in fact necessary
for PL surround sound.

It's probably more of a Joint vs Discrete stereo thing ?

You mean, depending on whether the left and right channels are encoded
separately (in the case of discrete stereo) or as middle/side? That
might account for the difference in bit-rate AFAIK.

Dolby Pro Logic
 

On 15/01/2012 11:27, Dave Plowman (News) wrote:
In [email protected] w.co.uk,
Andy wrote:
No, I'm not expecting them to have Dolby Digital, but do they carry
Dolby Pro Logic encoded in their stereo?

Any stereo signal can carry pro logic - that's the point of it. But how
much is made in that these days I don't know.


Yes -- I used to follow the American police series NYPD Blue (sadly
missed). My A/V amp. would never automatically switch to Dolby Surround
(the programmes were recorded this way, certainly the later series) but
if I manually switched I definitely got Dolby Surround/Pro-Logic audio
-- not simulated, for sure. I've also come across this on other Freeview
SD/Freesat SD broadcasts -- the audio is there, just not automatically
decoded. Something to do with PCM sound perhaps?



Clem