VHS to DivX reverse standards conversion

"Roderick Stewart" wrote in message
news
On Wed, 2 May 2007 10:41:30 +0100, "Agamemnon"
wrote:

So my question is, is there a VirtualDub filter that can do reverse
standards VHS conversions but taking a VHS recording sample at 720x576i
and
removing the lines that the recorder has interpolated, which are
obviously
not synced properly, so as to leave me with the original 384x288 VHS
source.

Where on earth did you get this idea from?!

From certain web pages which claim that VHS only records 288 lines in PAL
and 240 in NTSC;

"VHS Resolution

Concerning resolution, you should always keep in mind that VHS video is
roughly 320 x 240 pixels.

It's ********.

VHS machines have two heads, one for each field. Take the lid off one
and have a look. Open a service manual with a block diagram and have a
look. Both fields are recorded. All the lines are recorded. All 575
active picture lines are recorded, only with a video bandwidth of

You mean 576?

about 2.5MHz on a good day, but they're all there, interlace included
if it's from an unadulterated video source. Some may consider it
visually acceptable to reduce the vertical resolution of a VHS
recording to match the horizontal, but it is not inherently reduced in
this way by the technology itself. Vertical resolution is probably the
only thing about VHS that does preserve the full broadcast spec. You
shouldn't always believe what you read on web pages.

Well that will teach me not to trust the stuff they put on the web.

So the best way to DixX VHS tapes is to sample them at 720x576 and filter
out the interlacing artefacts and smooth out the noise using a temporal
smoother. Bitrates of 1024kbps will leave nasty smearing on fast movement
against plain backgrounds irrespective of resolution unless you do the
encode in two passes. 1500kbps will leave blocking in dark areas which is
not smoothed out by certified DivX DVD players because of the residual noise
on the VHS recording so its best to use 2048kbps.


Rod.

On Thu, 3 May 2007 16:00:00 +0100, "Agamemnon"
wrote:

VHS machines have two heads, one for each field. Take the lid off one
and have a look. Open a service manual with a block diagram and have a
look. Both fields are recorded. All the lines are recorded. All 575
active picture lines are recorded, only with a video bandwidth of

You mean 576?

I think most digital systems are made to handle 576 lines because it's
simpler than dealing with the half lines sparately, but the CCIR spec
for 625 line video has two lots of 25 lines blanked per frame. You do
the math, as they say.

Rod.

Agamemnon wrote:
After watching the Allo Allo! special on BBC2 on Saturday evening

What a fun-packed life you lead.

--
marc

"There are no such things as witches, and homosexuality is a choice of
how to masturbate. -- Aggy"

On 1 May, 17:18, "Agamemnon" wrote:
After watching the Allo Allo! special on BBC2 on Saturday evening where they
showed old news footage from Breakfast Time which was obviously sourced from
VHS I thought, can't the BBC do better

I noticed this as well, I have also noticed in some of the 100 best
of .. 50 best of.. etc programmes from C4 use very low quality clips
from programmes where the original tapes would certainly exist. Would
the Breakfast Time footage have been sourced privately or from the BBC
archives. Until relatively recently the cost and practicality of
storing hours of live footage (such as Programme as Broadcast footage
from live news/magazine programmes) meant that it was not done. Did
the BBC in the late 80's start keeping non-broadcast quality footage
for archive purposes. On an ITV programme on the Falklands war there
was very washed out/drained of colour footage of Leonard Parkin
introducing the ITN News at One - I would have thought that a
programme recorded in the early 80's would have been of better
quality.

Any expert here care to comment?

On 4 May 2007 12:59:05 -0700, AnnieslandJohn
wrote:

After watching the Allo Allo! special on BBC2 on Saturday evening where they
showed old news footage from Breakfast Time which was obviously sourced from
VHS I thought, can't the BBC do better

I noticed this as well, I have also noticed in some of the 100 best
of .. 50 best of.. etc programmes from C4 use very low quality clips
from programmes where the original tapes would certainly exist. Would
the Breakfast Time footage have been sourced privately or from the BBC
archives. Until relatively recently the cost and practicality of
storing hours of live footage (such as Programme as Broadcast footage
from live news/magazine programmes) meant that it was not done. Did
the BBC in the late 80's start keeping non-broadcast quality footage
for archive purposes. On an ITV programme on the Falklands war there
was very washed out/drained of colour footage of Leonard Parkin
introducing the ITN News at One - I would have thought that a
programme recorded in the early 80's would have been of better
quality.

Any expert here care to comment?

I'm not an expert, but I've seen the task of dubbing original material
on original C-format tapes onto digibeta being performed by work
experience trainees, and I don't think this sort of thing is unusual.
Presumably copying large volumes of material (in order to discard the
originals to save space of course) is seen as menial because it is
repetitive and unrewarding, and therefore cannot require any technical
skill or experience to do it properly, and by the time the truth is
realised it's too late because the original no longer exists.

In some cases, an original copy may exist somewhere but the sheer
logistics of finding it, and organising a machine to play it on, and
somebody that knows how to do it, just prove too much and they go with
the best copy they've got. Technical imperfections in old broadcast
material are hardly ever the result of technical inadequacies, just
human ones.

Rod.

I'm not an expert, but I've seen the task of dubbing original material
on original C-format tapes onto digibeta being performed by work
experience trainees

Oh dear!, this sounds very familiar .... In my own field (not
broadcasting), I worked for a company which had a close association
with a training agency whose trainees were placed with my company for
work placement. They were used to input live data to the extreme
detriment of its quality and accuracy. On paper this was a very clever
use of the trainees we were being paid to train, who could then work
on live data we would otherwise have to pay other staff to input. The
data input by the trainees who had no understanding of its
complexities was of such poor quality that we had to spend time
correcting and re-inputting it, or just turning a blind eye.

, and I don't think this sort of thing is unusual.

well, yes ....

Presumably copying large volumes of material (in order to discard the
originals to save space of course) is seen as menial because it is
repetitive and unrewarding, and therefore cannot require any technical
skill or experience to do it properly, and by the time the truth is
realised it's too late because the original no longer exists.

A classic case of false economy. Copying material onto new media for
preservation and to make it more accessible is a very reasonable thing
to do if done properly. However, the original should always be kept as
a safeguard. It is also the case that as the years progress, it may be
possible to extract a much higher quality copy from the original with
new digital technologies and enhancements than will be possible from
a copy of it made from with the technical and other (eg use of
untrained staff) limitations present at the time the copy was made.

In some cases, an original copy may exist somewhere but the sheer
logistics of finding it,

in theory this should not be a problem with a national public or
commercial broadcaster, however, as we know there were major problems
in the late sixties/seventies when large numbers of archive material
were discarded.

Technical imperfections in old broadcast
material are hardly ever the result of technical inadequacies, just
human ones.

Rod

Couldn't agree more. Thanks for an enlightening explanation. Anyone
have enything to add?

AnnieslandJohn wrote:


Technical imperfections in old broadcast material are hardly ever the
result of technical inadequacies, just human ones.

Couldn't agree more. Thanks for an enlightening explanation. Anyone
have enything to add?

Only that all BBC news programmes were supposed to be recorded on VHS
for non-broadcast consumption, and these are probably easier to access
than obsolete broadcast format copies.

Peter

Agamemnon wrote:

What I want to do is reverse standards convert upsampled 720x576 VHS to its
native VHS format as recorded on tape. I can already deinterlace it. I don't
want to deinterlace it. I want to get rid of all the interpolated frames
that the VCR has generated

VHS machines generate nothing (other than noise, of course...). They
record and play back the analogue 625/25 programme signal without
modification.


Peter

"Peter Hayes" wrote in message
om...
AnnieslandJohn wrote:


Technical imperfections in old broadcast material are hardly ever the
result of technical inadequacies, just human ones.

Couldn't agree more. Thanks for an enlightening explanation. Anyone
have enything to add?

Only that all BBC news programmes were supposed to be recorded on VHS
for non-broadcast consumption, and these are probably easier to access
than obsolete broadcast format copies.

Like VHS isn't already obsolete as well. It gone the same way as Betamax. I
just hope my VHS VCR doesn't break down.


Peter

On 2 May, 10:41, "Agamemnon" wrote:
wrote in message

ups.com...

On 1 May, 17:18, "Agamemnon" wrote:

So my question is, is there a VirtualDub filter that can do reverse
standardsVHSconversions but taking aVHSrecording sample at 720x576i
and
removing the lines that the recorder has interpolated, which are
obviously
not synced properly, so as to leave me with the original384x288VHS
source.

Where on earth did you get this idea from?!

From certain web pages which claim thatVHSonly records 288 lines in PAL
and 240 in NTSC;

"VHSResolution

Concerning resolution, you should always keep in mind that VHS video is
roughly 320 x 240 pixels.

You've got to love those web pages written by people who know nothing
whilst trying (and often succeeding) to sound authoritative.

In a world where anyone's thoughts can get to the top of Google if
enough people think they're worth linking to, these people can be
quite dangerous. At least the village idiot with too much time on his
hands used to be confined to the village!

Cheers,
David.