How to maintain color in mkv conversion?

[vato76]

Hello. Ive been trying to convert an mkv identically but each time for some reason the result color changes slightly yellow. Comparing the same frame, on a characters face the mkv shows more red where the converted file removes the red and has more yellow instead. This is regardless of the player. Ive tried converting to avi and mpg but the result is still the same. In playback the color is different but in screenshots they look the same. I checked my ffdshow settings and in picture properties all of the scales are "off". Im just wondering if this color change is inevitable. Thanks.

[jagabo]

How are you comparing the two? You can't open them both in media players side-by-side because one player will get video overlay and the other will not. Video overlay has its own proc amp controls so it will usually look different than the desktop (what the second player will be using).

Another issue you should be aware of is colorspace. Whether the input is rec.601 vs rec.709, whether it's properly flagged or converted in the output, and whether the player is displaying them properly. Unflagged HD is usually assumed to be rec.709. Unflagged SD is usually assumed to be rec.601. Displaying with the wrong colorspace will result in color shifts, especially in reds and oranges.

[vato76]

Whether i open them at the same time or individually they look the same for me in kmplayer. I also used VLC, but did get the overlay when both were open. Individually they still had the color difference tho.

In the kmplayer color control box the settings look identical when playing both files. How and where do i find the colorspace value that you mentioned? Thanks for the help.

[jagabo]

MediaInfo may show you the colorspace settings.

And just to be clear: there should be no significant shift in colors when you convert. So something is going wrong with your conversion.

[vato76]

Ok, with mediainfo both files have 4:2:0 colorimetry. Here is the info on the source file:

Complete name : E:\Full Movies\HD\Elizabeth Shue - Leaving Las Vegas (1995) [HD 720p].mkv
Format : Matroska
File size : 4.37 GiB
Duration : 1h 51mn
Overall bit rate : 5 615 Kbps
Encoded date : UTC 2010-02-10 14:53:58
Writing application : mkvmerge v3.0.0 ('Hang up your Hang-Ups') built on Dec 12 2009 15:20:35
Writing library : libebml v0.7.9 + libmatroska v0.8.1

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5.1
Format settings, CABAC : Yes
Format settings, ReFrames : 8 frames
Muxing mode : Container profile=Unknown@5.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 51mn
Bit rate : 4 749 Kbps
Nominal bit rate : 4 844 Kbps
Width : 1 280 pixels
Height : 688 pixels
Display aspect ratio : 1.660
Original display aspect ratio : 1.860
Frame rate : 23.976 fps
Resolution : 8 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.225
Stream size : 3.69 GiB (84%)
Writing library : x264 core 56 svn-667C
Encoding settings : cabac=1 / ref=5 / deblock=1:-3:-2 / analyse=0x3:0x133 / me=umh / subme=7 / brdo=1 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=2 / deadzone=21,11 / chroma_qp_offset=0 / threads=3 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / bime=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=2pass / bitrate=4844 / ratetol=1.0 / rceq='blurCplx^(1-qComp)' / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:0.4:15.0
Language : English

Audio
ID : 2
Format : DTS
Format/Info : Digital Theater Systems
Codec ID : A_DTS
Duration : 1h 51mn
Bit rate mode : Constant
Bit rate : 755 Kbps
Channel(s) : 2 channels
Channel positions : L R
Sampling rate : 48.0 KHz
Resolution : 16 bits
Stream size : 601 MiB (13%)
Language : English

And here is the converted one:

General
Complete name : C:\Documents and Settings\Administrador\Escritorio\Elizabeth Shue - Leaving Las Vegas (1995) [HD 720p].mpg
Format : MPEG-PS
File size : 4.10 GiB
Duration : 1h 51mn
Overall bit rate : 5 271 Kbps

Video
ID : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@High 1440
Format settings, BVOP : Yes
Format settings, Matrix : Default
Duration : 1h 51mn
Bit rate mode : Constant
Bit rate : 4 870 Kbps
Nominal bit rate : 5 000 Kbps
Width : 1 280 pixels
Height : 770 pixels
Display aspect ratio : 4:3
Frame rate : 23.976 fps
Resolution : 8 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.206
Stream size : 3.79 GiB (92%)

Audio
ID : 192 (0xC0)
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Duration : 1h 51mn
Bit rate mode : Constant
Bit rate : 192 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Video delay : 24ms
Stream size : 153 MiB (4%)

Can you show me where it has the colorspace settings? Thanks again.

[jagabo]

4:2:0 is the chroma subsampling, not the colorspace.

http://en.wikipedia.org/wiki/Chroma_subsampling
http://en.wikipedia.org/wiki/Rec._601
http://en.wikipedia.org/wiki/Rec._709

Colorspace, or Primary Characteristics aren't indicated in either of your files. They would be listed under "Format Settings, Matrix", "Encoding Settings", "Matrix Coefficients", "Colour Primaries", and/or "Transfer_characteristics" areas. Your files doesn't include any of those.

So given that the colorspace isn't specified in either file I would assume the MKV file is rec.709 (aka BT.709). And I would guess the player is playing the MPG file using rec.601 (aka BT.601) matrix. You should be able to specify the matrix in your MPEG2 encoder. Set it to rec.709 or BT.709, whichever terminology it uses. Then hope your player pays attention to the flag.

[vato76]

Next question: how do i find and tinker with the encoder settings? What if i wanted to try avi again? Im using AVS Video Converter but i cant find the matrix settings in the codec settings in there. And when i select mpg, the codec settings button is greyed out and i cant even access them.

The only codec filter i have installed is FFDshow, and in the encoder configuration panel i dont see any colorspace matrix settings in there for either mpeg-2 or H264. The only place its mentioned is under Input where it says "force input colorspace". Should i try that? Obviously i dont have any experience tinkering with these settings at all as i always leave them at defaults.

[jagabo]

Does AVS Video Converter let you add lines to the AVS script it uses? If so, you can download the colormatrix filter for AviSynth and use the following line to convert from rec.709 to rec.601:

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

ffdshow doesn't seem to have any way to specify the colorspace. HcEnc does. I don't know if there are any tools that let you flag it afterwards. Maybe MpegStreamClip?

[vato76]

Nope, i dont see any option for editing the script in AVS.

[jagabo]

If you can't find a tool to change the colorimetry flag in the MPG headers you may have to use different software for your conversions. I use AviSynth and HcGUI for that type of conversion.

A program is sometimes mentioned around here that lets you change MPG headers. I thought maybe it was MpegStreamClip but I checked and that wasn't it. Try searching through the Tools section here.

[davexnet]

Possibly restream ?
https://www.videohelp.com/tools/Restream