RGB question: 16-235 vs 0-255

[kb1985]

In what case I have to set the Input levels at 16-235 and output levels at 0-255? Do I have to do this while capturing video from analogue source through my Sony DV camera and I don't need to do this while copying the video recorded directly with the DV camera? Or do I need to do this in both cases?

[vhelp]

For DV CAM devices ...

For DV, the source video is already at 16-235 for YUV 4:1:1 format and because
the output nature is defined for TV viewing. During the DV transfer (assuming
DV CAM) the color range is processed as 16-235 already, through it's hardware)

For *other* DV devices, i.e., ADVC-100 etc ...

As far as DV from other devices, like the ADVC-100 then things are a
little different (and confusing to most people here) .. the color range
will be 0-255 instead. These devices are A/D converters. So, the color
range needs to be at 0-255 if color is going to be reproduced from other
"source devices" for maximum reproduction. In addition, such units (if they
provide) include a feature to switch between such color ranges. Take for
instance, the ADVC-100 device. It's an A/D converter box. This device
includes a feature to swtich color range (IRE) between 0.0 and 7.5 *but*
I believe that IRE and Color Range are one in the same thing:

* IRE 7.5 = 00-255
* IRE 0.0 = 16-235 = sRGB (studio RGB)

So, as I far as I know, there are no setting for color ranges 16-235 and
0-255 unless your software application provides such features, or your
hardware device provides it, as in the case for the ADVC-100 device.
.
I've never heard of it being incorporated on a DV CAM though.

-vhelp 3298

[kb1985]

So, as far as I get it, after capturing through A/D converter i have to add the filter?

[vhelp]

So, as far as I get it, after capturing through A/D converter i have
to add the filter?

No. Not exactly.

There are a few points to note.

* proper Encoder preporation
* source device (ie, vcr; calbe; etc)

Filtering (user manual) has virtually no effect. Its more or less,
a paint-job covering your actual canvas, and all you'll be doing
is throwing paint splats onto your canvas (video)

The range should be changed somewhere inside the conversion of the DV
sources YUV to RGB, becuase DV is stored inside a YUV container.
When you decode it, with a DV Codec, whatever the editer you
are using at the time (ie, vdub) it is (through the dv codec) converting
the YUV to RGB. Usually, this is converted to 0-255 range. AVIsynth
may be a little different. So, I'm not sure what your results would
be if used w/ AVIsynth. (I don't know your source)
.
If your DV is 16-235 then its up to the Encoder to convert to the
color range before encoding, or else, if using the frameserving
mechanism, (ie, AVIsynth) the conversion option, PC->TV or vise-versa,
(though I forget the function name) But, the mileage will vary from
this (I haven't really used it much in my testings) and I don't know
for sure, how accurate it is. But, you can try. I just don't know
the name of the function.

Another thing that most likely will give you varied results, is your
VCR. This is usually ( IRE 0 = 16-235 ) but things are pretty messy
there too.

The bottom line here is this..

If you don't know your source (devices, etc) then you are better off
just going with what you have. And, if you don't like (or feel) what
you have is good, then try a filter or two, and see where this takes
you.

I fear you are not in tune with your source

You also have to be in tune with your encoder.

-vhelp 3301

[kb1985]

I'm using Mainconcept Mpeg Encoder which encodes DV to MPEG. In advanced settings i have an option called "Input video is RGB 16-235". You mention that it should be "changed somewhere inside the conversion". Maybe that's the option?

[kb1985]

I'm not sure but it seems that when I open my DV material in Virtual Dub the colors seem "washed out". When I play the DV file in Media Player evrything seems ok. Maybe thats due to the RGB stuff?

I've converted one DV file to MPEG file using Mainconcept Mpeg Encoder with "Input video is RGB 16-235" oprtion activated. The colors seem "fresh" after that conversion. Is it done properly or have I just thrown some "paint splats" on my canvas?

And one more thing:
is this color space conversion loseless process?
i'm creating 4 GB MPEGs that will lay on my HDD for long days but maybe someday I will buy dvd-writer and would like to make DVD's from some (not all) of them. Will I have to change colorspace again then?

[vhelp]

I'm not too familiar with Mainconcept.

is this color space conversion loseless process?

I can't really say for sure. But, in my OP, no.. its probably lossy,
but will depend on which way you go ( 16-235 vs. 0-255 ) ..and that
depends on weather your source was 16-235 or 0-255, plus, also depends
on weather your device (ie, vcr; cable tuner; etc) is outpint at IRE 0
or 7.5 or whatever)

You have to test this out for yourself, and judge for weather or not
the video's color range looks right.
.
When a user captures any source into a contianer (DV avi for instance)
the final encoded MPEG should look like the input source. In other
words, OUTPUT = INPUT.
.
So, how does one test for this ?? ..good question. Below, is a rough
draft way of analyizing and comparing a set of OUTPUT vs. INPUT files.
.
HOW TO test OUTPUT = INPUT sources ...

After a capture project, and encoded to MPEG:

* Open your AVI source file inside vdubMOD

* Next, open your encoded MPEG-2 file inside another
  vdubMOD window

* position both vdubMOD windows ontop of each other,
  and position the video frame for both windows to
  match a frame in question.  (ie, frame number 17)
  and flip between them both, using the Ctrl+Esc key.

Now, if you notice any shift in colors, you'll know you have not properly
setup the encode process. But, if both windows show no sign of color
shift, you are doing things correctly.

That's about it. Have fun

-vhelp 3304

[kb1985]

I notice small color shift every time I encode to MPEG. It's really small but noticable. Source DV is slightly darker than MPEG.

Here are the screencaps:
http://kb.e9.pl/fotosy/styczen-maj2005/dv-to-mpeg/

[kb1985]

[please delete this post]

[kb1985]

OK... changed the DV codec and now it is much better, but I'm still not satisfied with the results. Please compare these 3 photos.

http://kb.e9.pl/fotosy/styczen-maj2005/dv-to-mpeg2/


Picture on MPG files seems slightly lighter to me than DV. Is it my fault or just some kind of MPEG specification? Or maybe there is nothing to worry about and I'm just oversensitive to this matter??

That;s in Virtual Dub. The difference is about 3000-4000 colours (counted with my graphic program).

When I play the files in Media Playter diferences are much smaller - only about 1000 colours, but still.

Is it another codec matter? Seems that media player and virtual dub load the files independly, using different codecs (?). Wht shoudl I do? It's quite fine to watch MPEG in media player, but I want to convert it to XVD and after passin g it through virtual dub it looses some colours.

[kb1985]

[please delete this post]