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| FredThompson |
| Posted: Jun 21 2008, 03:30 AM |
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Member
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I have not been successful loading MPEG-2 4:2:2 into VirtualDub 1.8.1 using fccHandler's MPEG-2 plugin for VirtualDub 2.6. Luma looks fine, chroma is almost all gone with splotches of odd chroma.
fccHandler, does it not include 4:2:2 support? |
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| fccHandler |
| Posted: Jun 21 2008, 04:11 PM |
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Administrator n00b
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It supports 4:2:2, but I never actually tested it.
I can confirm that the chroma is b0rked when video "color depth" is set to Autoselect, YV12, or YVU9. I'll try to fix that this weekend. In the meantime, try setting decompression color depth to YUY2 to work around it.
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May the FOURCC be with you... |
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| fccHandler |
| Posted: Jun 22 2008, 04:25 AM |
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Administrator n00b
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I've uploaded MPEG-2 plugin version 2.7, which should fix the 4:2:2 chroma problem:
http://fcchandler.home.comcast.net/Plugins/MPEG2
I had hard-coded "Autoselect" to return YV12 by default, which is perfect for VOBs (and most other MPEG files) but it's a terrible choice for 4:2:2 profile. Version 2.7 now chooses YUY2 if it detects 4:2:2 profile.
I hacked a new downsampling function just in case some clueless person deliberately chooses to decompress 4:2:2 to YV12. It does preserve interlacing as specified in ISO/IEC 13818-2. Unfortunately VirtualDub doesn't support interlaced YV12 so you'll end up with CUE in the preview. Mind you, that isn't the fault of VirtualDub or the plugin. It's simply because there's no standard for transport of interlaced YV12 in VFW.
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May the FOURCC be with you... |
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| phaeron |
| Posted: Jun 22 2008, 06:58 PM |
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Virtualdub Developer
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Nitpick: YV12 is a FOURCC for a format defined as having a progressive chroma layout. There is no such thing as "interlaced YV12." It's interlaced 4:2:0. |
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| FredThompson |
| Posted: Jun 23 2008, 01:05 AM |
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Member
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Thanks for the quick reply. I'll give the updated filter a whirl. (Edit: Works like a charm. Thanks a bunch!)
The source files are 4:2:2 interlaced MPEG-2 as claimed by TMPGEnc. Are they creating standard-incompliant files or what? |
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| fccHandler |
| Posted: Jun 24 2008, 09:58 AM |
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Administrator n00b
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No, TMPGEnc is perfectly compliant AFAIK.
The point I was making is that MPEG-2 4:2:2 profile should be decoded as 4:2:2. If one converts it to interlaced 4:2:0, there isn't a standard way to transport it in VFW/AVI. As phaeron said, the 'YV12' format isn't the same thing as MPEG-2 interlaced 4:2:0. For that matter, I don't think the 'YUY2' format is the same as MPEG-2 4:2:2 either...
I might have to reconsider that downsampling function, because I know phaeron is correct. It isn't giving what VirtualDub is asking for.
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May the FOURCC be with you... |
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| phaeron |
| Posted: Jun 25 2008, 05:08 AM |
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Virtualdub Developer
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YUY2 is 4:2:2 with coaligned chroma, so it's at least very close to MPEG-2. The color space might not be exactly the same. VirtualDub encodes and decodes it as Rec. 601, and more importantly, that's what kPixFormat_YUV422_YUYV in the plugin API specifies.
I could add interlaced 4:2:0 to the plugin API, even though there's no FOURCC for it... although it may take quite a bit of work in the blitter library. I added centered 4:2:2 and 4:2:0 to the dev tree recently and that was a royal pain. It's not going to be that useful, though, if it turns out the color matrix is wrong anyway for MPEG-2.
I wonder, what do DirectShow DVD decoders do? They can't all just resample to progressive chroma in software, that'd be stupid.
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| fccHandler |
| Posted: Jun 26 2008, 10:12 AM |
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Administrator n00b
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MPEG-2 allows the encoder to select from four different matrices to specify the coefficients it used to convert from RGB to YCbCr. Ideally the decoder can use the inverse to convert back to RGB, but it seems that many encoders don't bother to set this value correctly so I used to get a lot of complaints about washed-out colors. Because of that I set the default to Rec. 601, but you can still force it to honor the stream's matrix coefficients in MPEG preferences (VirtualDub-MPEG2) or extended open options (MPEG-2 plugin).
Just as a point of interest, my DirectShow decoder (CyberLink) can't decode a 4:2:2 profile MPEG. 
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May the FOURCC be with you... |
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