ColorMatrix v2.3

[colinb]

I'll shortly be using HC to encode some DV (camcorder) footage. I'll be feeding the DV AVI file to HC via an avisynth script.

Do I need to use colormatrix() in my avisynth script?

It's PAL DV if that is significant.

Well, I tried loading both the original DV AVI file and HC encoded m2v files into VirtualDub side by side and they appeared identical - this was without a call to colormatrix.

This surprised me because after a bit of searching I found that DV is supposed to be Rec.601 while HC expects its input to be Rec.709, so I would have thought that a conversion rec601->rec709 would be required before feeding HC.

So I then tried passing the original DV AVI file through a colormatrix 601 to 709 conversion and displayed this in VirtualDub alongside the original DV file (without colormatrix conversion). They looked almost identical too. Neither looked darker than the other. I did notice that on frames with intense red/orange these areas seemed slight darker or perhaps just more saturated on the 601->709 converted footage. This was the first time I have tried colormatrix and I was expecting to see a slightly more noticeable difference.

Anyway it looks like for PAL DV at least I don't need to use colormatrix - but I'm not sure why.

[Wilbert]

Just a quick note. I saw in the docs that you (Wilbert) had never come across a mixed colorimetry source. I've been transferring some of my TV DVD collections to x264 and I've found some of the season 1 SG-1 DVDs have mixed colorimetry. Thanks for the hints option!

Great! Could you upload a small vob which has this mixed colorimetry info?

This surprised me because after a bit of searching I found that DV is supposed to be Rec.601 while HC expects its input to be Rec.709, so I would have thought that a conversion rec601->rec709 would be required before feeding HC.

Sounds right (and yes, the difference is small). Could you upload a small part of that dv (10 frames)?

[EpheMeroN]

I have HD content that I am encoding to DVD using CCE 2.70, and was looking into using ColorMatrix on my sources.

DGIndex reports back a Colorimetry = ITU-R BT. 701 (1)

CCE also, by default, assumes ITU-R BT. 701 (1) coefficients correct? So, is there any reason to still use ColorMatrix? Or do I have it all wrong?

[Wilbert]

CCE also, by default, assumes ITU-R BT. 701 (1) coefficients correct? So, is there any reason to still use ColorMatrix? Or do I have it all wrong?

No, you are correct.

[actionman133]

Originally Posted by tritical

I've made a test version of colormatrix that is able to do all colorimetry type conversions (not just BT.709->BT.601 and BT.601->BT.709) with exact coefficients. It also has 3 options for value capping and coefficient scaling:

0.) cap input/output to [16,235(240)] range, and scale conversion coefficients (219/255,224/255)
1.) cap input/output to [0,255] range, and scale coefficients to (219/255, 224/255)
2.) cap input/output to [0,255] range, and don't scale coefficients (255/255)

The current version is always doing the equivalent of option 0. Would anyone be interested in this? If so I'll finish it up (mmx/sse2 conversions aren't finished), if not then I wont .

If you created a more comprehensive and precise filter (not to say Wilbert did a bad job, it's a great filter!), I would definitely use it. I am a precision control freak, so those extra options would be much appreciated.

[EpheMeroN]

Originally Posted by Wilbert

No, you are correct.

Good to know!

...but do you know if HD broadcasts use a range of 0-255 or 16-235?

[jsquare]

I have an old Samurai movie in B/W, when encoded with Xvid it looks a bit too bright and washed out, DGIndex is reporting the colorimetry as "ITU-R BT.470-2" and the frame type seems hybrid(it changes from Interlace to Progressive constantly). By adding ColorMatrix() to the script my encode looks acceptable, but I have a couple of questions:

Is the default command ColorMatrix() all I need or should I include some other settings?

Should I add ColorMatrix() to all my future encodes?

[Boulder]

Does ColorMatrix even affect BW stuff?

[jsquare]

Originally Posted by Boulder

Does ColorMatrix even affect BW stuff?

Probably not, but it seems to "clamp" Luma/Chroma to CCIR-601 values as stated on the docs.

[Boulder]

That's a job for Limiter()..I'm sure using it is faster than using ColorMatrix with B/W stuff.

[Oline 61]

I don't quite understand this. If I have a DVD that uses BT.709 according to DGIndex, do I need to use Colormatrix? If so, what settings?

[Wilbert]

What is your final format? What is your encoder?

As an example: If you are encoding to mpeg-4 (which uses BT.601), you will need the conversion.

[Oline 61]

I am just going AVISynth to MeGUI/x264 CLI. Another thing I just noticed is that when I preview the VOB in DGIndex it says BT.709, but after it finishes creating a d2v project file it says SMPTE 170M. So what would be the proper settings for me to use?

[Wilbert]

I am just going AVISynth to MeGUI/x264 CLI. Another thing I just noticed is that when I preview the VOB in DGIndex it says BT.709, but after it finishes creating a d2v project file it says SMPTE 170M. So what would be the proper settings for me to use?

If true, this would be a bug in DGIndex (since SMPTE 170M = BT.601, and SMPTE 240M = BT.709). Could you check this with the latest DGIndex?

[Oline 61]

Using latest DGIndex version:
The first picture is the windows after completely saving the d2v project.

The second picture is a screenshot while running a preview.

[Oline 61]

Is there a definitive way to tell which of these colorimetries is correct?
BTW, when I try to use ColorMatrix(d2v="VTS_01_1.d2v")
it tells me that multiple colorimetry types were detected in the d2v file.

[Wilbert]

BTW, when I try to use ColorMatrix(d2v="VTS_01_1.d2v")
it tells me that multiple colorimetry types were detected in the d2v file.

Yes, neuron2 hinted at this possibility. You need to find out, by scrolling through the video, when the colorimetry changes. I guess the main movie is BT.709, but after the credits some black frames are SMPTE 170M? Please confirm.

If that's indeed the case, i would apply ColorMatrix to the whole movie (it doesn't do anything when a frame is black, since it corrects chroma).

[Oline 61]

Looks like your right. If I play it starting near the end it changes to 170M right before reaching the end of the file. Thanks for helping, I will use ColorMatrix()

[Boulder]

Another option is to enable hints output in MPEG2Source and set ColorMatrix accordingly.

[15081947]

After going through this entire thread I am trying to tabularise the colormatrix usage for Divx/Xvid conversion.

Anything -> Divx/Xvid
------------------------
Source Colorimetry--------ColorMatrix
ITU-R BT.470-----------------No
ITU-R BT.601-----------------No
ITU-R BT.709-----------------Yes
SMPTE 170 M-----------------No
SMPTE 240 M-----------------Yes

Please feel free to correct it.

Thanks