bt.709 and CCE

[fjhdavid]

Dear all,

I use DVD-RB and CCE with the "colormatrix" conversion command because CCE requires bt.709 coeff in order to re-encode (like HC).

Then I read the burnt DVD on my DVD player (an oppo hd981) and I choose "RGB output over hdmi".
I assume that the player does the conversion between internal YV12 data stored on the DVD to RGB for the hdmi output.

which matrix does the player use, bt.601 or bt.709? or Am I totally wrong as there no need for conversion?

thanks
Francois

[jdobbs]

The default for DVD is Rec.709 -- so your player should play it back correctly.

[fjhdavid]

I thought the same things, but oppo told me that they use bt.601 for the internal YCB to RGB conversion.

after reading the CCE owners guide, it seems that CCE itself work in bt.601.

where does come the assumption that CCE work with 709 coeff?
(the CCE owner's manual is speaking about bt.601, (see p.51 and p.52)
and this link too:
http://forum.doom9.org/showthread.php?s=&threadid=53770
(Question.12)

[Video Dude]

CCE outputs Rec.709.

Q12 refers to "Luminance Level".
Since DVD-RB already inputs YUY2 into CCE, that conversion is not done by CCE.

[fjhdavid]

DVD-RB inputs YUY2 into CCE, then it means that it will input the "DVD orginal color matrix" and it tells only that, it could be rec.601 or rec.709

BUT, where did you read that CCE output Bt.709? because if it's true, we don't need "colormatrix avisynth filter" anymore.....

I think CCE doesn't write any color matrix in its header and by default, we are thinking it is bt.709

but the DVD compliant color matrix has always been rec.601 as DVD is only SD

anyway, give a try with getgray calibration disc (which is 601), and you will see if CCE output bt.601 or bt.709

[jdobbs]

Here's some text from the Colormatrix documentation (my boldfacing):

There are several ways to convert a YUV stream to RGB. The most well known one, uses Rec.601 coefficients. It is for example used in the color conversion routines of AviSynth, VirtualDub and XviD/DivX. When playing back a XviD/DivX the stream is converted to RGB using Rec.601 coefficients. The main issue is that sometimes other coefficients are used for the YUV to RGB conversion (the other two are Rec.709 coefficients and FCC coefficients). A problem arises if a stream is encoded using one set of coefficients (Rec.709 coefficients for many dvd streams for example), and somewhere in the reencoding-processing-playback chain a different set of coefficients is assumed (Rec.601 coefficients for the XviD/DivX decoder or FCC coefficients for TMPGEnc/QuEnc or Rec.709 coefficients for CCE). You will get a slightly color distortion, which looks like a change in brightness (it's not really a change in brightness, the colors are just slightly off).

How do you know what set of coefficients are using when encoding a MPEG-2 stream? Sometimes the coefficients are stored in the header of the MPEG-2 file (the "matrix coefficients" field in the "sequence display extension"). Newer versions of GSpot will be able to read this part of the header, but also DGDecode (with Mpeg2source(info=1)) can be used to view them. If this extension field is not present in the header of the MPEG-2 file, the specs say we are supposed to use the default Rec.709 coefficients (0.2126, 0.7152, 0.0722).

The Colormatrix filter is applied before the encoding.

CCE's site spells out that it outputs in MPEG-2 in accordance with ISO/IEC13818-2, ITU-T Rec.H262 (MP@ML only). CCE doesn't add a sequence_display_extension.

The specification for 13818-2 spec page 53 states:

"In the case that sequence_display_extension() is not present in the bitstream or colour_description is zero
the chromaticity is assumed to be that corresponding to colour_primaries having the value 1."

and

the value 1:

"1 Recommendation ITU-R BT.709"

If CCE were not outputting in Rec.709, and was not setting the sequence_display_extension(), it would be writing a non-compliant stream... which I highly doubt.

In writing/testing DVD-RB I can assure you that the vast majority of DVD (SD) movies either don't have sequence_display_extension present or have it with a matrix coefficients value set to "1" -- meaning it uses Rec.709. The exceptions I see on a common basis are seen in menus and extras and video from television -- which often are Rec.601 -- and have sequence_display_extension present with a value of "6".

[fjhdavid]

I think we are facing a real problem.

I completely agree with you that in mpeg2 stream if no header is present, it is bt.709 assumed and that CCE output doesn't exhibit any color matrix header (but maybe it is a mistake!)

BUT, all the DVD spec says that DVD MUST be bt.601 compliant because they are SD (I found many place on the WEB and datasheet where it is written)

In addition, a lot of DVD player use bt.601 (I asked OPPO developper and Philips and if you read the DVD re-encoded by CCE in this case, you will face a problem)

last, if you look at the page 51 and 52 of the CCE owner guide it is written that RGB to YCB is bt.601-5 compliant and the equation gives coeff 601)
this link:
http://forum.doom9.org/showthread.php?s=&threadid=53770
tends to say the same things that CCE is expecting bt.601 as input , so you must not use any colormatrix conversion before input in CCE...

maybe a mail to CCE will answer our question?

PS: a lot of PAL DVD commercial are also bt.601...and getgray which is a wellknow calibration DVD is bt.601 also (I asked its author)

[dragongodz]

(but maybe it is a mistake!)

do you realise how long CCE has been around and used by professionals ? i think someone would have noticed before now if this was the case.

BUT, all the DVD spec says that DVD MUST be bt.601 compliant because they are SD (I found many place on the WEB and datasheet where it is written)

please give links that say this.

In addition, a lot of DVD player use bt.601 (I asked OPPO developper and Philips

use how ? if they are looking at a dvd with no sequence_display_extension and saying that means its 601 then they are the ones that have it wrong. jdobbs post already showed that.

if you look at the page 51 and 52 of the CCE owner guide it is written that RGB to YCB is bt.601-5 compliant and the equation gives coeff 601

this link:
http://forum.doom9.org/showthread.php?s=&threadid=53770
tends to say the same things that CCE is expecting bt.601 as input

sorry but no it does not. it is specifically talking about the conversion of RGB input to YCbCr when done by CCE and the luminance range of the conversion. it does not specify what the output is etc.

a lot of PAL DVD commercial are also bt.601

do you mean commercial PAL dvds ? if so i call B.S. to that. i tested that already and the vast majority are 709, NOT 601. i even found 1 that used 420m.

[fjhdavid]

a link to DVD player from oppo:

http://www.avsforum.com/avs-vb/showt...pp=30&page=144
(response 4308, 4317 and 4320)
and

http://www.avsforum.com/avs-vb/showt...pp=30&page=145
(response 4324)

look to neuromancer post which is working in oppo

you can also go to getgray site where it is explained that SD DVD MUST be bt.601

for the CCE owner guide manual:
it is said: if you enter the CCE encoder with a RGB signal, it will convert it according to bt.601, then it means that we must NOT use the colormatrix filter if the dvd is bt.601 before entering and that we have to use a bt.709 to bt.601 conversion for a dvd bt.709...(i said that because I use a green correction avisynth filter)

THEN why would CCE use bt.601 for input and then bt.709 to output (double conversion)? wouldn't it have been easier to leave everything in bt.709 from the input to the output (especially if all DVD were bt.709)?

in addition, I don't prefer bt.601 over bt.709 (you will see in the link I provided that I am a strong advocate of bt.709.....), I just want to know, because I have a lot of DVD which are bt.601 and you have one that are bt.709....

maybe if you own CCE, a quick mail should answer the question...

[Wilbert]

a link to DVD player from oppo:

http://www.avsforum.com/avs-vb/showt...pp=30&page=144
(response 4308, 4317 and 4320)

Not convincing:

response 4308:

DVD is YCbCr 4:2:0 BT.601 IIRC.

No evidence here.

response 4317:

"main level (ML) - A range of proscribed picture parameters defined by the MPEG-2 video standard, with maximum resolution equivalent to ITU-R BT.601 (720 x 576 x 30)."

I'm not sure what this statement means here (which parameters are they referring to?). In any case it is referring to that maximum resolution 720 x 576 x 30. Does it also refer to which coefficients are used? I don't know. Perhaps others know or can look it up?

response 4320:

DVDs are encoded like Neuromancer said. Upconverted SD DVDs should be output with 709 because when a TV sees a 720p, 1080i or 1080p signal it assumes its HDTV standard which uses REC 709.

More statements without evidence.

response 4324:

The MTK solution decodes at BT.601. Once this signal is sent to the Faroudja chipset, the Faroudja chipset will then sample it at the native BT.601 (480p) or convert it to BT.709 (720p, 1080i, 1080p).

This chipset will then output the resulting signal to the one which is most appropriate to the native decoding of your display.

Well ok, this chipset works that way. The main question still remains, why ????

or the CCE owner guide manual:
it is said: if you enter the CCE encoder with a RGB signal, it will convert it according to bt.601, then it means that we must NOT use the colormatrix filter if the dvd is bt.601 before entering

This can be either true and false. It all depends on how the final YCbCr->RGB conversion is done upon display. If it's done correctly (ie using Rec.709, at least that's my opinion and many others in this thread), then their statement is false.

I've added a reply in that thread. Let's wait if they come up with any credible evidence.

[45tripp]

Is there a tool to insert color matrix coefficients into the mpeg2 header?

I know you can strip the color coefficients with restream,
but what about addition?

ty

[dragongodz]

because I have a lot of DVD which are bt.601 and you have one that are bt.709

actually what i said is i have many that are 709 and i have 1 that is 420M. of the ones i checked i found exactly 0 to be 601.

a link to

i asked for links to show the dvd specs say dvds MUST be 601 as you claimed. none of those links do that. opinions do not count as fact.

[dragongodz]

maybe this will help

http://www.dvddemystified.com/dvdfaq.html#3.4

Pictures are subsampled from 4:2:2 ITU-R BT.601 down to 4:2:0 before encoding, allocating an average of 12 bits/pixel in Y'CbCr format.

note it doesnt say its subsampled TO bt.601 Y'CbCr. so for RGB or 4:2:2 footage then it would appear to expect bt.601 to sample down. now if CCE is only going to encode to bt.709 surely it knows to sample down to the correct Y'CbCr to do so.

[fjhdavid]

Ok, I am sure we will find the answer, but remember, DVD-RB is a tool to re-encode DVD in order to play them with a PC or with a DVD player.

For the DVD player, the MTK pre-processor is used in a lot of products (the output of the MTK chip is then going to a faroudja or an anchorbay or an HQV chip for de-interlacing or scaling, and then for scaling they use bt.709 for 720p and 1080p as it is specified in the HD spec but not SD)

and the fact is that MTK is 601 compliant!

so even if CCE is bt.709, you won't read correctly your DVD in a lot of commercial or standalone player....as today, this is a fact, and it should be better to ask CCE guys to be bt.601 compliant!

this a problem, don't you think? do you think that CCE guys don't know the fact about MTK is 601? so why would they go to bt.709?...surprising if it is true

guys from DVE essential and Getgray told me also that DVD is bt.601 and they are (at least for DVE) wellknown in the DVD calibration tool (and i am sure they bought the DVD specs even if it is 5000 dollars)

[dragongodz]

The MTK solution decodes at BT.601. Once this signal is sent to the Faroudja chipset, the Faroudja chipset will then sample it at the native BT.601 (480p) or convert it to BT.709 (720p, 1080i, 1080p).

and the fact is that MTK is 601 compliant!

is it decoding using bt.601 though or is it decoding to bt.601(thus a conversion if not bt.601 already) ? the second would be basically a reverse of the bt.601 RGB conversion i mentioned earlier.

guys from DVE essential and Getgray told me also that DVD is bt.601

you will have to excuse me for having more faith in the evidence of all the commercial dvds out there and real viewable specs ,such as the mpeg2 13818-2, than just the word of these people. especially when you said

BUT, all the DVD spec says that DVD MUST be bt.601 compliant because they are SD (I found many place on the WEB and datasheet where it is written)

now if you could get someone from a major studio or such to say categorically that dvd must be encoded USING bt.601, not just in RGB colour conversion, then you may have something.

[fjhdavid]

maybe you are right, guys from MTK and Joe Kane from DVE are wrong...but let me have a doubt about that....

DVE is used by professional calibrator and studio broadcaster to calibrate their SD and HD stuff (and DVE is available in two different disc, one for SD in bt.601 and the second for HD in bt.709)

MTK is used in philips, Oppo ...

Cirrus Logic (an another wellknown and wide used DVD player decoder chip also use bt.601)

but have a look to:
http://www.pinnaclesys.com/files/Mai...whitepaper.pdf

Page 4 and page 15

and
http://www.dvddemystified.com/dvdfaq.html#1.1

section 3.4

but, I have an idea: I will re-encode tonight a DVD bt.601 and look with DGindex if CCE write something in the header. If it writes bt.601, it means that CCE simply use the matrix color of the original DVD and dosen't change it...
Then for your DVD bt.709, CCE will write nothing as it is bt.709 by default....

an another point is that you refer to 13818-2, but which version? 1995, 1996, 2000 with 2002 correction included or with 2007 corection...
if it is the 1995 version, DVD didn't exist at this time, and I am not able to download the other versions

[dragongodz]

MTK is used in philips, Oppo ...

Cirrus Logic (an another wellknown and wide used DVD player decoder chip also use bt.601)

which doesnt answer the question i asked at all.

Page 4 and page 15

which only talks about resolution. so no proof there that output must be bt.601 colormetry.

section 3.4

so you missed i already posted a link to that and commented on it ?

I will re-encode tonight a DVD bt.601 and look with DGindex if CCE write something in the header. If it writes bt.601, it means that CCE simply use the matrix color of the original DVD and dosen't change it...

and what if it does convert it to bt.709 and then doesnt write the header, so should be assumed bt.709 per mpeg2 specs, what then ?

[fjhdavid]

if the CCE re-encoded DVD show a bt.601 with DGindex, it means that there is no bt.709 in CCE !

(you didn't answer to my question about the 13818-2 version)

[Wilbert]

if the CCE re-encoded DVD show a bt.601 with DGindex, it means that there is no bt.709 in CCE !

It doesn't. Other people have checked that.

an another point is that you refer to 13818-2, but which version? 1995, 1996, 2000 with 2002 correction included or with 2007 corection...
if it is the 1995 version, DVD didn't exist at this time, and I am not able to download the other versions

That's a good point. Mine is "ISO/IEC 13818-2: 1995 (E)". Do you have a more recent one?

[kumi]

By the way, if the OP's goal is to see if his player is correctly displaying CCE-encoded video, why doesn't he simply encode 2 clips in CCE:

A) SMTPE colorbars, Rec.709
B) SMTPE colorbars, Rec.601

...then burn them to DVD and examine the output on his standalone player. Colorspace conversions using the wrong set of coefficients (Rec.709 vs. Rec.601, or vice-versa) are easy to spot, aren't they?