Fons Adriaensen wrote:
I'd agree with what Sampo wrote in a previous post: it should be
possible to find out the encoding by analysing the recordings.
That would be interesting.
From the sound designer's seat I need to say that by listening
undecoded and decoder and by watching a goniometer or a phase
or correlation meter, it is very difficult to find out whether the
recording is
UHJ encoded or not. (That is why digital UHJ would have needed a flag
in the rptocol in the first place. What did I say? It's sooo nice to be able
to say this :-) )
This is especially difficult with acoustic recordings, but Ambisonically
mixed multitrack recordings are a little bit easier, depending on the
amount of added reverberation and other effects and on which instruments
they have been added.
A centrally panned mono signal shows up in the goniometer as a narrow
oval because of the phase shift. You can see this also from other mono
signals that have been panned in the front sector, say +/- 30 degrees from
center front. You need to use your ears and a goniometer at the same time.
If you'd like to analyse a possible encoding, I would say; look first at
centrally panned mono signals and their phase differences between the
channels.
In all other directions the panned mono signals cannot be detected as
"easily". They look about the same to the eye as all other content that
has large phase differences between the channels. The ear is a more
sensitive tool with this. The Chronos movie audio is a good example.
I sometimes compared the audio track of the DVD and the audio
of the CD release. They differ at places, individual sequences have
been edited differently to the video and the CD, but the mix is also a
little
bit different at places. There is a remarkable difference in the
reverberation
and the width of the soundfield, the CD is much more "open" and decodes
much wider and spacious than the DVD audio. (The DVD audio is two track
stereo, not multichannel.)
By ear I would say that the video soundtrack is not UHJ but the CD could be.
Or - the video audio has been narrowed by audio or data compression
or narrowing by panning and thus part of the surround content has
been removed.
- - -
There is also another interesting CD, which includes UHJ tracks and
Holophonic
tracks on the same disc:
World Record, WWCD002 (Mfg. in Japan, U.K. Distribution)('84)
The sleeve doesn't say which tracks are which, so I sometimes in the
Grey Past tried to find it out by listening. The result of my one man
listening group
was that tracks 1-4, 8-9 and 13 are most likely Ambisonics and tracks
5-7 and
10-12 are Holophonics. My guess was based on that Holophonics provides an
outside-the-head sound image, while Ambisonics doesn't.
Eero
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