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  1. Member
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    The source is HD. DGDecode definitely says its Rec.709 when using (Info=1)

    When I make a .d2v and preview the file in Virtualdub the reds look more like Rec.601 reds. When I use Colormatrix(mode="rec.709->rec.601") the reds look more like Rec.709 reds which is the opposite of what I would expect. Here is my sample.

    http://www.multiupload.com/WOBTYWLDSX


    Usually I can tell the difference in reds straight away, but perhaps my eyes are deceiving me on this occasion. I would appreciate any help.
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  2. I haven't seen the sample yet, but it's always possible the source was prepared incorrectly.

    <later...>

    I have the sample now. Note that DgIndex reports the colorimetry as BT.709 with an asterisk. That means the colorimetry isn't specified in the file and it is assuming BT.709 (because it's HD).

    I'm not really sure what the colors are supposed to look like but I think it looks more natural in VirtualDub after Colormatrix(mode="rec.709->rec.601"). I'd look at a wider variety of shots before deciding.
    Last edited by jagabo; 23rd Apr 2011 at 08:11.
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    Thanks. Yeah, I noticed the asterisk but as this is HD I thought it had to be Rec.709. I am not sure it is possible for HDTV to be broadcast as Rec.601, but perhaps it can be prepared as Rec.601 and broadcast as Rec.709?

    To my eyes, after converting to Rec.601 the reds have that orange saturated look one expects with Rec.709, but perhaps I am wrong. Either way, I don't suppose I can do anything about it. I don't want to encode a Rec.709 DVD even with the colorimetry flagged as such, so I suppose I have to convert to Rec.601 and accept the colors as they are. Thanks again.
    Last edited by Richard1485; 23rd Apr 2011 at 08:36.
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  4. But how do you know the frock is supposed to be red not orange? I think the flesh tones look better in VirtualDub after Colormatrix(mode="rec.709->rec.601"). But the shot is in a predominantly green setting so it wouldn't surprise me if the colors are off. I'd look at more material before final judgement.
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    Also, the programme makers have almost certainly applied colour correction and/or a 'film effect' to the footage. So I wouldn't necessarily expect the video to look natural/accurate.

    If I'm using mplayer correctly (emphasis on the 'if'), forcing the decoding to use BT.709 makes the reds more orange, and the greens less blue. Selecting BT.601 makes the reds redder, and the greens bluer. The former gives the video a slightly 'sepia' tone, the latter looks slightly more natural. What the programme makers intended is hard to say.
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  6. Originally Posted by intracube View Post
    If I'm using mplayer correctly (emphasis on the 'if'), forcing the decoding to use BT.709 makes the reds more orange, and the greens less blue. Selecting BT.601 makes the reds redder, and the greens bluer.
    That's right.
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    Originally Posted by jagabo View Post
    But how do you know the frock is supposed to be red not orange?
    You're absolutely right. I don't know for sure. The difference between the two simply looks like the difference that I usually see when Rec.709 hasn't been converted properly to Rec.601; it made me suspect that something had gone wrong.

    Originally Posted by intracube View Post
    forcing the decoding to use BT.709 makes the reds more orange, and the greens less blue. Selecting BT.601 makes the reds redder, and the greens bluer. The former gives the video a slightly 'sepia' tone, the latter looks slightly more natural.
    That's exactly how the difference appears to me too.

    EDIT: Hypothetically, if I converted the footage to SD without using Colormatrix and flagged the MPEG-2 stream as SMPTE170M, could I achieve the latter, more natural look?
    Last edited by Richard1485; 23rd Apr 2011 at 10:51.
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  8. Originally Posted by Jeff B View Post
    Hypothetically, if I converted the footage to SD without using Colormatrix and flagged the MPEG-2 stream as SMPTE170M, could I achieve the latter, more natural look?
    Yes.
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    ^^^ Thanks. I shall try it both ways and see which I like the best.
    Last edited by Richard1485; 23rd Apr 2011 at 18:27.
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    Originally Posted by Jeff B View Post
    Hypothetically, if I converted the footage to SD without using Colormatrix and flagged the MPEG-2 stream as SMPTE170M, could I achieve the latter, more natural look?
    I haven't heard of SMPTE170M before.

    If I understand correctly, BT.601 defines both NTSC and PAL (SD) chromacity coordinates - as shown in section 2.6 of this pdf:
    http://www.itu.int/rec/R-REC-BT.601-7-201103-I/en
    'SMPTE170M' relates to NTSC's chromacity coordinates (1987 onwards), whereas 'EBU Tech 3213' is for PAL:
    http://en.wikipedia.org/wiki/RGB_color_space#Specifications
    Is that right?

    Rec.709 on Wikipedia says that in practice, conversion between colourspaces is 'rarely performed'.

    Also, the uploaded video is 59.94fps, and looks like it was originally shot at 24 or 25fps. Were you going to IVTC it and convert to a PAL framerate to remove the judder?
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  11. Originally Posted by intracube View Post
    I haven't heard of SMPTE170M before.
    It's exactly the same as ITU-R BT.601.
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    Whoops! Looks like I missed two posts earlier on. (I hate this threaded view thing.) My comment above was meant as a reply to jagabo.

    And yes, manono is right. SMPTE170M is of course ITU-R BT.601.

    Also, the uploaded video is 59.94fps, and looks like it was originally shot at 24 or 25fps. Were you going to IVTC it and convert to a PAL framerate to remove the judder?
    No; it inverse telecines fine to 23.976, so I'm encoding an NTSC DVD. Although I did do a little PAL encoding recently, I almost always encode to NTSC.
    Last edited by Richard1485; 23rd Apr 2011 at 18:33.
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