Home cinema - HDTVs and audio

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- - HDTVs and audio (http://www.homecinemabanter.com/showthread.php?t=73978)

Steve Thackery wrote:
Mark Carver wrote:

It doesn't on any HD sets, they are all set to 3ish % overscan,
which means that rescaling is going on, even on native 1920 x 1080
broadcasts.

True, but as with Roger, my Sony will let me set it to exact pixel
mapping.

I know it will, and so does mine, what is it you didn't understand
about my original responce to Jim ? ;-)

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

Mark Carver wrote:
Steve Thackery wrote:
Mark Carver wrote:

It doesn't on any HD sets, they are all set to 3ish % overscan,
which means that rescaling is going on, even on native 1920 x 1080
broadcasts.

True, but as with Roger, my Sony will let me set it to exact pixel
mapping.

I know it will, and so does mine, what is it you didn't understand
about my original responce to Jim ? ;-)

Don't call him a ponce!

Bill

In article ,
Jim Lesurf wrote:

1) Is it standard for such sets to accept audio in via HDMI and then copy
that out via an SPDIF coax/optical outlet for connection to a decent
external DAC?

An alternative, depending on your audio equipment, is to send the
output by HDMI too, using the audio return channel. This has the
advantage (from my point of view) that you can use the TV's volume
control - volume up and down are sent through the HDMI connection.

Are middle-of-the range panasonics likely to have 3 HDMI sockets?

My 2010 model has three on the back and one on the side, useful for
temporary connections.

-- Richard

On Wed, 01 Jan 2014 17:14:59 +0000, Roger Wilmut
wrote:

In article ,
Mark Carver wrote:

R. Mark Clayton wrote:

It doesn't on any HD sets, they are all set to 3ish % overscan,
which means that rescaling is going on, even on native 1920 x 1080
broadcasts.

My Sony Bravia is set to a slight overscan by default, but there is a
setting for the HDMI inputs to be 'pixel perfect', i.e. no overscan and
an exact pixel for pixel match to the source. Occasionally you get fine
lines at the edges of the picture as a result.

Back in the days of analogue TV tuner expansion cards (when 30GB HDDs
had just become affordable) and the typical PC didn't have quite
enough 'grunt' to effectively do the mpg compression on-the-fly to
avoid burning up HDD space at the rate of a 100MB per minute), I used
to do most of my viewing using the PC and wondered why on earth anyone
would put up with the outrageous overscan typical of most domestic TV
sets of the day (circa 2000).

Later, sometime in 2005, when I installed my first DVB-T adapter, I
still had the same opinion (but the bit rates employed by BBC1 and
BBC2 were still quite respectable back then).

It's only in recent years with the bit rates now only at around 50 to
75% of what they used to be that I can see a need to offer an
'overscan' option.

With mpeg compression, the edges of the transmitted picture will
exhibit compression artifacts at a noticably higher level than
elsewhere. With the less aggressive compression used in the early
days, this wasn't too much of a distraction but since then, they've
become more pronounced and now I can see some merit in emulating
'overscan'.

With a "Pixel Perfect" display, rescaling to achieve this 'overscan'
is just an unnecessary act of stupidity. A superior method when the
transmitted pictures exactly match the display resolution is to blank
out the offending edges. This will shrink the display area slightly
but, provided the bezel is of the correct colour (pitch black, of
course!), the result will be more acceptable than adding scaling
artifacts to a picture already compromised in quality due to the lossy
compression employed by the broadcast system.

In the case of a "Full HD FreeView" set with a 1080 line dispalay
panel this would only really benefit Full HD broadcasts. When such a
set is used to receive SD broadcasts which have to be upscaled anyway,
they can be upscaled to create an actual overscan to eliminate the
edge compression artifacts when the viewer chooses the overscan option
since whatever upscaling artifacts are there are unlikely to be
noticably worse for this display mode.

It's quite possible that I'm describing exactly the process in use
for the HD overscan option, I'm not familiar with HD TV technology
since I've no burning desire, as yet, to "upgrade" anytime soon.
--
Regards, J B Good

Richard Tobin wrote:
Jim Lesurf wrote:

1) Is it standard for such sets to accept audio in via HDMI and then copy
that out via an SPDIF coax/optical outlet for connection to a decent
external DAC?

An alternative, depending on your audio equipment, is to send the
output by HDMI too, using the audio return channel.

Then you're at the mercy of whatever DAC in in the amp, it also requires
HDMI 1.4 support in TV and amp, not likely to be an issue for new kit.

This has the advantage (from my point of view) that you can use the
TV's volume control - volume up and down are sent through the HDMI
connection.

You don't need to use ARC to get that, my amp does support ARC but TV is
older and only has HDMI 1.3, so I use SP/DIF from TV to amp, and the CEC
channel lets the TV's remote control the amp's volume (once the TV's
internal speakers have been deselected) in addition turning on/off the
TV makes the amp follow suit.

On Wed, 01 Jan 2014 14:58:02 +0000 (GMT), Jim Lesurf wrote:

At long last I've decided to take the plunge and buy an HDTV 'Freeview'
set. Almost certainly an LED Panasonic of modest size. I'd welcome some
answers to a few pretty basic questions, mainly wrt the audio side of
operations.

Right, I have a new(ish) Panasonic, bought in September from Richer Sounds -
I'd recommend RS or JL as the prices are good (especially taking into
account no (added) delivery charge and the 5-year warranty).
Mine is probably mid-range and is this one:
http://www.richersounds.com/product/...ana-txl50et60b
or - oh, looks as if JL's not doing the same model now
http://www.johnlewis.com/electricals...048/c800005013

1) Is it standard for such sets to accept audio in via HDMI and then copy
that out via an SPDIF coax/optical outlet for connection to a decent
external DAC?

Yes, I have HDMI from the AVR then SPDIF to the AVR on one socket and the
Humax Freesat PVR on another.
I don't have HDMI Service enabled in the AVR as that takes the standby power
from 1W to ~19W!

If the answer to (1) is 'yes':

2) Is it normal to then be able to mute the TV's own speakers so you just
can use a hifi and the external DAC for the audio?

Simple - turn the TV's volume to 0.

3) Does that normally then bypass any 'volume control' of the TV set? Or is
this user-choosable, or what?

Not on mine and also the headphone socket doesn't cut the speakers. Instead
of running the AVR at 45W all the while - not needed for most programmes -
I've a pair of active PC speakers. The volume control on the PVR will
control these but not the on on the TV, so not very good.

4) Does HDMI ensure audio-video synch? Either from the TV's digital output,
or by telling the HDMI source and allowing a digital spdif output from that
to be delayed to match? Or?

It seems to be OK. I had to adjust the sync. once, for a recording on the
PVR, but it is OK for both DTTV and DSTV.

It would be convenient from my POV is the TV acted simply as a 'pass
though' for the audio from external sources - e.g. DVD player. So ensured
lip-synch by otherwise allowed the audio samples to be 'as from the source'
without any sounds from the TVs speakers. But is the norm? Or is there a
problem here?

It could be possible but I don't yet know. On my model, the BD player (LG)
won't show on the TV through either the AVR or its own direct connection.

Also:

Are middle-of-the range panasonics likely to have 3 HDMI sockets?

Mine has. RS has reasonable details, or try:
http://www.panasonic.com/uk/consumer...sions/led.html

Allow no 'overscan' so a 1:1 scaling of HD sources?

Yes.

I'll ask about such things in the shop. But some comments here to clarify
what I should be able to expect would be helpful.

Cheers,

Jim

Panny shops probably no good; RS - pot luck but can be good; same with JL
really.
--
Peter.
The gods will stay away
whilst religions hold sway

On 01/01/2014 17:18, Jim Lesurf wrote:

Never had any trouble with this. Kindly the BBC outputs a couple of
minutes a day of test card with speaker and synch tests to allow you to
check everything is correct. Any delay will be set specific.

When is the HD testcard broadcast and on what 'station'?

It used to be carried on BBC HD, but that's now been converted to BBC 2
HD, and sadly no longer has any downtime to carry the test signals.

There is 03:00hrs to 06:00hrs that could be used, but that space is used
for back to back BBC 2 promos

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

Johny B Good wrote:

With mpeg compression, the edges of the transmitted picture will
exhibit compression artifacts at a noticably higher level than
elsewhere.

Are you sure? The edges? That's not my experience as a viewer
(although I don't know anything much about the MPEG compression
algorithm).

As a viewer, the compression artefacts become most obvious on large
areas of similar colour which move, such as mist. I certainly haven't
spotted anything odd about the edges.

Could you provide a reference for me to read up more about it?

--
SteveT

Jim Lesurf wrote:

Using the TVs 'volume control' something I'd tend to avoid if possible as I
have no idea how well it can scale the values.

My TV just seems to send "+" and "-" commands to the amp rather than
absolute values, my amp is set for a 0-100 scale with 0.5 unit steps
which is finer than the TV's inbuilt volume control (0 to 63 I think)
the amp has the option of using a dB scale but my brain doesn't
naturally use logs.

Steve Thackery wrote:
Johny B Good wrote:

With mpeg compression, the edges of the transmitted picture will
exhibit compression artifacts at a noticably higher level than
elsewhere.

Are you sure? The edges? That's not my experience as a viewer
(although I don't know anything much about the MPEG compression
algorithm).

As a viewer, the compression artefacts become most obvious on large
areas of similar colour which move, such as mist. I certainly
haven't spotted anything odd about the edges.

Could you provide a reference for me to read up more about it?

I always thought the crappy edges were scaler artifacts rather than
mpeg/bitrate related - but then I could be wrong.