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Old 12th August 2015, 19:21   #1  |  Link
OvejaNegra
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colormatrix with bluray source, yes or no?

When doing conversions using dgdecode with DVDsources to xvid/x264 i always used color matrix.

The same applys to bluray -> x264 ?
Im serving my source like this:

Code:
v=LWLibavVideoSource("H:\TORA\ch1\00000.m2ts.lwi", stream_index=-1)
a=LWLibavAudioSource("H:\TORA\ch1\00000.m2ts.lwi", stream_index=1)
AudioDub(v,a)
Spline36Resize(1280,720)
Do i still need to use colormatrix (or any other correction method) on this source?

Do i need to put anything on the x264 command line (like coheficients, color transfer or anything like that)?

Or just serve and encode?

I used search but the only information i found was about using colormatrix when scaling and downsizing.

thanks.
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Old 12th August 2015, 21:58   #2  |  Link
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Assuming your source is bluray, Colormatrix is only needed if you do a resize from HD to SD.
If your source is not bluray, you only want to use colormatrix if you for some reason are not happy with original colorimetry or do a resize from SD to HD
So the answer is no.

Quote:
Originally Posted by OvejaNegra View Post
Do i need to put anything on the x264 command line (like coheficients, color transfer or anything like that)?
Yes. Always. Regardless of whether you use colormatrix or not. If this info is not present, the player or other software must guess it. Which is fine, usually, but not always. Once new 4K BDs will be out, this is will likely be even more important. If you specify that, you don't have to actually use colormatrix at all (assuming the player/renderer will obey this information). But converting (if needed) AND specifying it is a safest choice.

Last edited by Keiyakusha; 12th August 2015 at 22:20.
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Old 13th August 2015, 03:23   #3  |  Link
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Thanks for your help:
according to media info from mpchc the m2ts reports nothing (maybe there is a better tool to extract info from m2ts stream)
the source is bluray

i have doubts with these options:

videoformat -> undef / unknown
fullrange -> on?
colorprim ->bt709? (do al the bluray discs use bt709?)
transfer ->bt709? (do al the bluray discs use bt709?)
colormatrix->bt709? (do al the bluray discs use bt709?)
chromaloc = 0?
nal-hrd->none?

i found this info, dont know if its accurate:

Quote:

More specifically:

–colormatrix specifies what coefficients are used when converting YUV to RGB. This is the one you want to use.
–colorprim specifies what color primaries (see for example the Wikipedia page about sRGB) the RGB uses. Setting this properly most likely requires knowledge of the studio equipment used to master the stream and/or its settings, so just leave it undefined. No one without a color calibrated monitor would ever notice or care, even if decoders/renderers actually supported this.
–transfer specifies the gamma curve used for the RGB. Like –colorprim, setting this correctly probably requires knowledge you don’t have, so don’t set it at all. Again, only people with calibrated studio monitors will ever notice or care.

TL;DR: Use --colormatrix bt709 if your source is a HD transport stream; --colormatrix bt470bg if it is an SD transport stream.
source: http://mod16.org/hurfdurf/?p=116
thanks again
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Old 13th August 2015, 08:03   #4  |  Link
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I think youi'll probably want Full range samples to be off. As I recall "On" is the default and is usually wrong (as YUV video should have Y in the 16-235 range). It trips me up all the time, and I end up with lower-contrast videos.
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Old 13th August 2015, 12:08   #5  |  Link
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The way I understand it:

colormatrix = the method for converting the video to RGB on playback. It should always be bt709 for HD.
transfer = the gamma curve. bt709 & bt601 use the same gamma curve.
colorprim = once the video is converted to RGB, it'd display most accurately on a monitor calibrated to.... ie bt709 or bt601 primaries. I think HD displays are supposed to be bt709.

The Video Usability Info has absolutely no effect on how the video is encoded. it's just information written to the video stream.

As far as I know you'd probably only want to specify colormatirx when encoding, unless you can obtain the other info from the video stream, but I doubt any player would pay any attention to anything but colormatrix anyway.

Fullrange = off (default). Pretty much all video is limited range (with the exception of formats such as mjpeg and maybe DV)

Chroma sample location. I don't touch it myself. http://git.videolan.org/?p=x264.git;...;f=doc/vui.txt
nal-hrd http://www.chaneru.com/Roku/HLS/X264...gs.htm#nal-hrd

From the DGIndex manual:
Colorimetry - Displays the colorimetry scheme used by the stream. Note that if the stream does not declare the colorimetry, then ITU-R BT.709* is reported for HD video, and ITU-R BT.470-2* is reported for SD video. The * character indicates that the stream did not declare the colorimetry

From the colormatrix manual:
hints:
DGDecode v1.20 or newer can output colorimetry hints in the video stream which ColorMatrix can read in order to automatically determine the source coefficients. To enable this, set info=3 in mpeg2source() and set hints=true in ColorMatrix() as shown below:


The way I understand it, by default Colormatrix will convert bt709 to bt601, which you want it to do for standard definition but not for high definition. For standard definition you'd normally use it in combination with DGDecode like this:

Mpeg2source("D:\video.d2v", info=3)
ColorMatrix(hints=true)

Which I'm pretty sure would be the same as:

Mpeg2source("D:\video.d2v", info=3)
ColorMatrix(hints=true, mode="Rec.709->Rec.601")

For HD video I think you'd need to use it like this so it'll convert to bt709 when the source isn't bt709, but when it is bt709, it'll leave it alone.

Mpeg2source("D:\video.d2v", info=3)
ColorMatrix(hints=true, mode="Rec.601->Rec.709")

I generally don't use colormatrix at all and just assume HD is bt709 and SD is bt601 and re-encode it as is. If I'm downscaling (or upscaling) I'd manually convert the colours and set the x264 colormatrix option accordingly. That'd be regardless of the format of the source video (mpeg2 or h264 etc) ie for downscaling HD to SD:

ColorMatrix(mode="Rec.709->Rec.601", clamp=0)

Last edited by hello_hello; 14th August 2015 at 14:32.
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Old 13th August 2015, 15:07   #6  |  Link
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Quote:
Originally Posted by hello_hello View Post
The way I understand it, by default DGDecode will convert bt709 to bt601
Maybe I misunderstood you, but DGDecode does not perform any colorimetry conversions.
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Old 13th August 2015, 15:11   #7  |  Link
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always a pain in the ass when "color" stuff gets to be the problem
converting "matrix" alone is, not very correct more or less
"matrix" "transfer" and "primaries" are a set of interactive parameters work together as one to represent a certain part of colors from CIE 1931 (the very first color standard covering every single visible color to human vision, and device independent of course, kind like the royal of all color related stuff)
primaries = how red exactly is the red here (green, blue likewise), it decides the coordinates of 3 elementary colors (cannot be represented as some mixed stuff of other colors, they are the purest thing here, they get to mix each other to produce other colors) on CIE system
transfer = a function that connects physical intensity and perceived intensity (aka gamma)
matrix = a matrix to separate luminance and chrominance
so, see, HDTV got a different "matrix" not because "oops, the old bt.601 sucks ass, I don't like it, let's make some crazy new crap", "709" matrix is there because HDTV picks different primaries from SDTV, so a new matrix is needed to separate luminance and chrominance of the image based on this new primaries.
pointless to apply "709" matrix on clips with "601 NTSC/PAL" primaries cuz you can't get correct luminance and chrominance with this matrix, the "luminance" is not the exact luminance and so is the chrominance, the "matrix" does not serve as it's supposed to, and "601" matrix on "709" primaries, likewise
if you are that desperate to change the color system, don't just convert the matrix, convert to CIE 1931 and apply a whole new set of different color system.
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Old 13th August 2015, 18:58   #8  |  Link
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Quote:
Originally Posted by hello_hello View Post
The way I understand it, by default DGDecode will convert bt709 to bt601
Same as videoh i have troubles understanding this part and everything that follows. DGDecode can only report colorimetry if it is specified in headers (most of the time not)

Quote:
Originally Posted by hello_hello View Post
Which I'm pretty sure would be the same as:
Mpeg2source("D:\video.d2v", info=3)
ColorMatrix(hints=true, mode="Rec.709->Rec.601")
No. ColorMatrix(hints=true) is placebo and in most real-life situations does nothing with regard of the colorimetry because most streams on dvds do not have colorimetry info specified and assumed to be Rec.601 by DGDecode. (and if it will be specified, it will be Rec.601 anyway) It may perform some other stuff by default like levels clipping but its usefulness is questionable.
This might be different for HDTV mpeg2 captures though. I'm not sure if they have proper Rec.709 flags and what happens in this case, but it would be very bad to convert it to Rec.601 and if DGDecode is doing this, that would be a serious bug/flaw. So getting rid of ColorMatrix entirely seems like a good idea. Only use it for SD<->HD conversions.
Quote:
Originally Posted by colormatrix docs
ColorMatrix corrects the colors of MPEG-2 streams of dvds. More correctly, many MPEG-2 streams use slightly different coefficients (called Rec.709)
Sorry, but this is bullshit.
DVDs whatever don't have colorimetry specified or do have it specified. In 1st case you assume "601" and set x264 accordingly, in second you take whatever is specified and specify it in x264. In either case you don't need to convert anything (unless you do a SD-HD resize). So if ColorMatrix(hints=true) is converting something, whatever output you get is wrong,

Edit: only if you want to convert video to RGB somewhere inside the avs script, you must specify correct colorimetry. But you don't need colormatrix for that either, avisynth's ConvertTo*** functions have a way to deal with that. Perhaps this was not always the case.

Last edited by Keiyakusha; 13th August 2015 at 19:36.
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Old 13th August 2015, 19:42   #9  |  Link
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Every time i see something about colormatrix or color representation it becomes a discussed topic, the information is very unclear / obscure most of the time.

Fullrange: Histogram("classic") on avisynth confirms that the video is in fact limited so: Fullrange -> off (default)
Colormatrix: DGAVC Index reports BT709* (undetermined-> assumed) so i dont know what to put here , BT709 because "all HD Streams are with bt709" or leave it undefined"

As far as i remember the problem with colormatrix and SD sources was the fact that MPEG4 always assumed BT601 so you have to convert BT709 to BT601 BUT with h264 you can specify whatever you want, so no need for colormatrix if you are converting to h264.

BUT AGAIN: Since most of the time BT601 is expected on SD streams and BT709 is expected on HD streams (and some renderers expect it like that) you need to use color matrix for resolutions changes.

So basically:
BT709 for SD-> HD output (convert if source is not) and flag to x264
BT601 for HD-> SD output (convert if source is not) and flag to x264 (nothing to do if using xvid).
HD -> HD:
BT709 -> Do nothing and flag to x264
BT601 -> Convert to 709 and flag to x264
Unspecified -> ????? Do nothing at all or flag to x264

Please correct me if im wrong
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Old 13th August 2015, 19:55   #10  |  Link
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Quote:
Originally Posted by OvejaNegra View Post
the video is in fact limited
Videos on TV/DVD/BD and likely every official streaming service are never fullrange. Only if you'll do it yourself. They could be technically PC range but that would be some noise or other garbage most of the time.

Quote:
Originally Posted by OvejaNegra View Post
DGAVC Index reports BT709* (undetermined-> assumed)
That is what you'll see for most HD streams. Set it to 709 in x264.

Quote:
Originally Posted by OvejaNegra View Post
MPEG4 always assumed BT601 so you have to convert BT709 to BT601
The problem is, colormatrix docs only mention DVDs. DVDs are never BT709.
Edit: in fact if a DVD player strictly follows the spec and the stream is flagged as 709, it is supposed to refuse to play it.
True that MPEG4/ASP (divx/xvid) does not have colorimetry information, but if this info is not present, assumption is made by the player/renderer based on resolution, not format. MPEG4 itself does not assumes anything.

Quote:
Originally Posted by OvejaNegra View Post
BT709 for SD-> HD output (convert if source is not) and flag to x264
BT601 for HD-> SD output (convert if source is not) and flag to x264 (nothing to do if using xvid).
HD -> HD:
BT709 -> Do nothing and flag to x264
BT601 -> Convert to 709 and flag to x264
Unspecified -> ????? Do nothing at all or flag to x264
Marked bold - no. Why? Never convert anything. However you are very unlikely to find such a stream anyway. Edit: but if you'll chose to convert it will not be wrong.
For unspecified, assume that all DVD are 601, all Blurays are 709 and specify accordingly (note that 4k blurays will use yet another colorimetry)

Last edited by Keiyakusha; 13th August 2015 at 21:55.
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Old 13th August 2015, 21:20   #11  |  Link
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Just don't convert anything
Avisynth got no ability to convert primaries last time I checked
And converting matrix alone is not very reasonable like I said at #7
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Old 14th August 2015, 05:55   #12  |  Link
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Thanks to all.
I remember all the avisynth examples about using color matrix with dgdecode for converting to Xvid, and the reasons were not very clear to me.
But now i have two final questions:
What was the point of color matrix (before the hdtv/bluray existence)? An mpeg2 stream with BT709? From where? TV capture?
This: http://forum.doom9.org/showthread.php?t=82217 mentions

Quote:
ColorMatrix corrects the colors of mpeg2 streams of dvds. More correctly, those mpeg2 streams are encoded using a different set of coefficients as used by AviSynth's color conversion routines or by the XviD/DivX decoders
Again, what streams with bt709?

Keiyakusha:
Quote:
The problem is, colormatrix docs only mention DVDs. DVDs are never BT709.
Edit: in fact if a DVD player strictly follows the spec and the stream is flagged as 709, it is supposed to refuse to play it.
Second final question:
Is there any proper way of converting from one to another on avisynth (without using colormatrix), i know this would imply converting to and from RGB but i want to know.

Quote:
if you are that desperate to change the color system, don't just convert the matrix, convert to CIE 1931 and apply a whole new set of different color system.
Thanks
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Old 14th August 2015, 06:31   #13  |  Link
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Quote:
Originally Posted by OvejaNegra View Post
Second final question:
Is there any proper way of converting from one to another on avisynth (without using colormatrix), i know this would imply converting to and from RGB but i want to know.
nah, it goes way beyond RGB, CIE 1931 is required here (all RGB colorspaces are derived from CIE 1931)
and you'll need a 3D expression to go from RGB to XYZ, something like mt_lutxyz, but with higher precision, like floating point
you can do it with std.Expr in vaporsynth, and, I don't really know if there is an "avisynth Expr" out there
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Old 14th August 2015, 06:56   #14  |  Link
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Quote:
Originally Posted by OvejaNegra View Post

Quote:
ColorMatrix corrects the colors of mpeg2 streams of dvds. More correctly, those mpeg2 streams are encoded using a different set of coefficients as used by AviSynth's color conversion routines or by the XviD/DivX decoders
Again, what streams with bt709?
I guess only author of the plugin can answer that. Other than that, we can't even guess. That quote makes absolutely no sense.
"corrects the colors of mpeg2 streams of dvds" - there's nothing to correct
"encoded using a different set of coefficients as used by AviSynth's color conversion routines" - What different set? What routines? Avisynth is not converting anything. This is only matters when you convert from YUV to RGB, and you don't. And even if you do, avisynth supports both conversions, Rec601 and Rec709

Quote:
Originally Posted by OvejaNegra View Post
Is there any proper way of converting from one to another on avisynth (without using colormatrix), i know this would imply converting to and from RGB but i want to know.
Not sure if I got you right, but assuming you have Rec601 YV12 source, to make it 709 this should do the job:

ConvertToRGB32(matrix="Rec601").ConvertToYV12(matrix="Rec709")

But this is more destructive than using colormatrix.

Last edited by Keiyakusha; 14th August 2015 at 07:01.
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Old 14th August 2015, 14:36   #15  |  Link
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Quote:
Originally Posted by videoh View Post
Maybe I misunderstood you, but DGDecode does not perform any colorimetry conversions.
Yeah, I should have said colormatrix. I've corrected my previous post.
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Old 14th August 2015, 15:00   #16  |  Link
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Quote:
Originally Posted by Keiyakusha View Post
No. ColorMatrix(hints=true) is placebo and in most real-life situations does nothing with regard of the colorimetry because most streams on dvds do not have colorimetry info specified and assumed to be Rec.601 by DGDecode. (and if it will be specified, it will be Rec.601 anyway) It may perform some other stuff by default like levels clipping but its usefulness is questionable.

Sorry, but this is bullshit.
DVDs whatever don't have colorimetry specified or do have it specified. In 1st case you assume "601" and set x264 accordingly, in second you take whatever is specified and specify it in x264. In either case you don't need to convert anything (unless you do a SD-HD resize). So if ColorMatrix(hints=true) is converting something, whatever output you get is wrong,
You're free to do it however you like, but me.... I try to make sure my SD encodes are BT.601 and my HD encodes are BT.709. If that means converting the colours when downscaling/upscaling, I convert them. That way, if a player isn't paying attention to the info written to the video stream and the colorimetry used is based on resolution, the video should display correctly.

Quote:
Same as videoh i have troubles understanding this part and everything that follows. DGDecode can only report colorimetry if it is specified in headers (most of the time not)
Wrong. If it's not specified, DGDecode reports bt.601 for SD and BT.709 for HD. It's in the DGDecode html file. You're bound to have trouble following if you're assumptions are incorrect.

Quote:
Originally Posted by Keiyakusha View Post
The problem is, colormatrix docs only mention DVDs. DVDs are never BT709.
Edit: in fact if a DVD player strictly follows the spec and the stream is flagged as 709, it is supposed to refuse to play it.
True that MPEG4/ASP (divx/xvid) does not have colorimetry information, but if this info is not present, assumption is made by the player/renderer based on resolution, not format. MPEG4 itself does not assumes anything.
I don't use colormatrix when encoding DVDs myself, but there's plenty of old posts here at doom9 where posters have stated GSpot shows a DVD as BT709. Reputable posters too, such as the author of AutoGK (len0x).

The colormatrix docs might only mention DVDs but the DGDecode docs mention HD video too.

Colorimetry - Displays the colorimetry scheme used by the stream. Note that if the stream does not declare the colorimetry, then ITU-R BT.709* is reported for HD video, and ITU-R BT.470-2* is reported for SD video. The * character indicates that the stream did not declare the colorimetry.

So if you're using DGDecode's hints with colormatrix, I see no reason why it shouldn't work exactly as I described for HD video.

Mpeg2source("D:\video.d2v", info=3)
ColorMatrix(hints=true, mode="Rec.601->Rec.709")

That should convert to bt.709 if the source isn't bt.709, and leave the colors alone if it's already bt.709. Personally, I don't think it's worth bothering with. Just as DVDs all seem to be bt.601, all HD video is BT.709, so colormatrix won't be doing anything.
Except of course for the plethora of x264 standard definition bt.709 encodes in existence that were encoded from HD sources without converting the colours, but aside from the sins committed by some people when downscaling and re-encoding, HD should always be BT.709 and SD should be bt.601.

Last edited by hello_hello; 14th August 2015 at 17:10.
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Old 14th August 2015, 15:40   #17  |  Link
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Quote:
Originally Posted by OvejaNegra View Post
As far as i remember the problem with colormatrix and SD sources was the fact that MPEG4 always assumed BT601 so you have to convert BT709 to BT601 BUT with h264 you can specify whatever you want, so no need for colormatrix if you are converting to h264.
When re-encoding YV12 video, if you don't convert to another colorspace during encoding (converting to RGB to keep VirtualDub filters happy might be an example) then you're just encoding the video "as-is". The colorimetry choice isn't made until it's converted to RGB on playback. So if it's YV12 in and YV12 out, the colorspace won't change unless you deliberately change it.

It's not completely accurate to say MPEG4 (ie Xvid) or x264 "expect" bt.601, because while that's true, it's only when the encoder input is RGB. Then the encoders have to decide which colorimetry to use when converting to YV12.
If you're re-encoding a YV12 Bluray/DVD video though, the encoders just re-encode it. They're oblivious to the colorimetry required for playback, so it doesn't matter if it's bt.601 or bt.709. In the case of Xvid, it can't write the colorimetry info to the video stream as x264 can, so ideally you should ensure it's correct (bt.709 for HD and bt.601 for SD) because the player will pick the colorimetry based on resolution. So converting bt.709 to bt601 when downscaling is a good idea. In the case of x264, it can write the colorimetry info to the video stream and in a perfect world all players would use the written colorimetry. In the real world though, I doubt that's always the case. Depending on how you're playing video using a PC.... the player and renderer etc.... and assuming the video card drivers work correctly and/or don't interfere, there's still a pretty good chance the colorimetry info written to the stream will be completely ignored and the choice will be made based on resolution.

Quote:
Originally Posted by OvejaNegra View Post
Again, what streams with bt709?
If I remember correctly the DVD spec and the mpeg2 spec don't always agree. Even though DVDs contain mpeg2 video.
DVDs are supposed to be bt.601, but for standard definition mpeg2, if there's no colorimetry written to the video stream the spec says you're supposed to assume bt.709, not bt.601. So the difference there might account for it.

If you search through old threads here, you'll find posts where it's claimed a DVD is bt.709. Originally, DGDecode reported bt.709 if there was no colorimetry info written to the video stream, because the original consensus was DVD video should be bt.709.
That's long since changed, and DGDecode now reports bt.601 for DVDs when there's no colorimetry info written to the stream. Most of the early posts on colorimetry and colormatrix here are before my time, but you may still find screenshots indicating VirtualDub displays DVD video with the wrong colorimetry.... or something along those lines.
I don't know why the consensus changed, but I suspect DVD video hasn't changed and crappy video card drivers were causing the wrong colorimetry to be used in the early days. That's just my theory.....
There was an Avisynth page containing a list of video card drivers explaining when those drivers get things wrong, but I can't find it at the moment. It may have been removed. The info would be very out of date.

By the way, if you do convert to RGB and back to YV12 during encoding, by default Avisynth and VirtualDub and their filters all convert to RGB using bt.601. That's fine, even for HD, because by default they'll all convert the RGB back to YV12 using bt.601 as well. It's one of those times when two wrongs does make a right. If you convert to RGB and back using the same colorimetry each time, the colors won't change, even if it's not the same colorimetry that'll be used to convert to RGB on playback.

Last edited by hello_hello; 14th August 2015 at 15:44.
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Old 14th August 2015, 15:59   #18  |  Link
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I have a question... while I'm thinking about it. Good old AutoGK has two colour correction options in it's settings. When colour correction is enabled you can choose between "accurate" and "fast". AutoGK comes with colormatrix, so I assume that's what it uses for colour "correction" if required (in combination with hints from DGDecode), but I've never known what the difference is between the two colour correction options. Does anyone know?
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Old 14th August 2015, 16:06   #19  |  Link
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Originally Posted by hello_hello View Post
If I remember correctly the DVD spec and the mpeg2 spec don't always agree. Even though DVDs contain mpeg2 video.
DVDs are supposed to be bt.601, but for standard definition mpeg2, if there's no colorimetry written to the video stream the spec says you're supposed to assume bt.709, not bt.601. So the difference there might account for it.
DVD Video uses a sub-set of MPEG-2, see here.
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Old 14th August 2015, 17:04   #20  |  Link
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Originally Posted by feisty2 View Post
always a pain in the ass when "color" stuff gets to be the problem
converting "matrix" alone is, not very correct more or less
"matrix" "transfer" and "primaries" are a set of interactive parameters work together as one to represent a certain part of colors from CIE 1931 (the very first color standard covering every single visible color to human vision, and device independent of course, kind like the royal of all color related stuff)
primaries = how red exactly is the red here (green, blue likewise), it decides the coordinates of 3 elementary colors (cannot be represented as some mixed stuff of other colors, they are the purest thing here, they get to mix each other to produce other colors) on CIE system
transfer = a function that connects physical intensity and perceived intensity (aka gamma)
matrix = a matrix to separate luminance and chrominance
so, see, HDTV got a different "matrix" not because "oops, the old bt.601 sucks ass, I don't like it, let's make some crazy new crap", "709" matrix is there because HDTV picks different primaries from SDTV, so a new matrix is needed to separate luminance and chrominance of the image based on this new primaries.
pointless to apply "709" matrix on clips with "601 NTSC/PAL" primaries cuz you can't get correct luminance and chrominance with this matrix, the "luminance" is not the exact luminance and so is the chrominance, the "matrix" does not serve as it's supposed to, and "601" matrix on "709" primaries, likewise
if you are that desperate to change the color system, don't just convert the matrix, convert to CIE 1931 and apply a whole new set of different color system.
That all sounds nice in theory, but in reality if I downscale HD video and convert it to bt.601, the SD version looks the same as the HD version to me, color-wise. A question.....
If I didn't convert the colours and simply wrote bt.709 to the video stream, on the occasions I'm using a media player that pays attention to the colorimetry info, in what way would the video display differently?. The original required bt.709 when converting to RGB on playback, while the encode now requires bt.601 because I converted the colours.

Maybe I'm missing something but I thought bt.601 and bt.709 used exactly the same gamma, and even if the colorprim parameter wasn't generally ignored by players, why wouldn't it still be correct? If the source video displays as it should on a bt.709 calibrated display, shouldn't the downscaled version also display the same way?

The original video probably looks like this:

Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

After I convert the colours and downscale I normally only tell x264 to write the matrix coefficients, but if I was more enthusiastic, or I always knew the correct values, I'd get it to write all three like this:

Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.601

Why wouldn't the encode display exactly like the source given I've only changed the matrix coefficients to reflect the change in colorimetry?

Last edited by hello_hello; 14th August 2015 at 17:07.
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