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OMFInput for DVCPRO 25 PAL (4:1:1) 
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Joined: Sun, 2012/07/22 12:31 am
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Unread post OMFInput for DVCPRO 25 PAL (4:1:1)
Hello tateu,

Your old plugin "OMFInput" seems to be able to read my OMF files, which were captured from the camera tapes. Unfortunately for me, contrary to normal DV25 PAL, which is 4:2:0, the color subsampling for DVCPRO 25 PAL (and DVCPRO 25 NTSC as well) is in fact 4:1:1. So even though the video is visible, the plugin decodes it as 4:2:0, assuming that it is DV25 PAL. The result is as shown in the attached .jpg file.

If I were any sort of a programmer, I would attempt to fix this myself from source, but I'm not. If you have time, could you let me know if there is a change you could make to the plugin to read DVCPRO 25 PAL files correctly (that is, not to assume 4:2:0 because it is PAL, but in fact use 4:1:1 chroma subsampling). Thank you in advance for your help and time. Best regards, Ned Barth


Attachments:
File comment: .jpg export from VirtualDub using "OMFInput" Avisynth plugin
OMFFrame00000.jpeg
OMFFrame00000.jpeg [ 198.8 KiB | Viewed 7884 times ]
Sun, 2012/07/22 12:58 am
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Joined: Sun, 2005/04/03 7:02 pm
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Location: Los Angeles, CA USA
Unread post Re: OMFInput for DVCPRO 25 PAL (4:1:1)
I'm not sure I can do anything about that. I'm at the mercy of whatever open source DV decoding library I can find and use. I used the Cedocida DV library. I am looking through the source code for it and the decode_NTSC_DVSD function runs the video data through a YUV411_to_YUY2 function. The decode_PAL_DVSD function runs the video data through a YUV420_to_YUY2 function. And I don't see anything that mentions DVCPro so it may (probably?) doesn't even handle that.

If you can get me a sample omf file, I'll certainly take a look...


Sun, 2012/07/22 4:34 am
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Unread post Re: OMFInput for DVCPRO 25 PAL (4:1:1)
Also, give FFMpegSource2 a try. It opens my test omf files with DV25, DV50, Mpeg30 and Mpeg50, except it adds a bogus extra frame at the end, but that can easily be trimmed off.

I don't have any DVCPro test files and FFmpegSource2 does not open my uncompressed or mjpeg sample files.


Sun, 2012/07/22 12:20 pm
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Joined: Sun, 2012/07/22 12:31 am
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Unread post Re: OMFInput for DVCPRO 25 PAL (4:1:1)
Thank you, tateu, for your amazingly quick response. I have been able to open the .omf clip in Virtualdub by renaming it with the ".dv" extension (when I do this even QuickTime can open it) and then using QTSource in my Avisynth script. Since I got your responses, I also tried FFMpegSource2 but have not yet succeeded in opening the clip in Virtualdub by this method. I did find a small (about 5MB) .omf clip which I could upload somewhere for you to take a look at. I'm sorry I don't have anything under 256KB so I can't attach it to this post.

As far as the Cedocida codec issue goes, you've hit the nail on the head with your comments about the source code library. In effect what I need is for the Cedocida codec to be "tricked" into sending the data through the YUV411_to_YUY2 fork even though it's not an NTSC clip. DVCPRO 25 PAL is apparently exactly like DV 25 PAL, except for the fact that it uses 4:1:1 while DV 25 PAL uses 4:2:0.

Let me know if you have an upload destination you prefer and I will upload the sample DVCPRO 25 .omf clip. Thanks again, Ned Barth


Sun, 2012/07/22 1:30 pm
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Unread post Re: OMFInput for DVCPRO 25 PAL (4:1:1)
I have no idea what is causing that but I modified the cedocida library to use the YUV411_to_YUY2 function instead of the YUV420_to_YUY2 and all that did was add a green tint to the lower half of the screen. There is more going on here than just 4:2:0 vs 4:1:1 but I think it is beyond me to figure out.

You have found one workaround, rename to .dv and uses QTInput. I also have a never-completed-version of OMFInput that can use VFW codecs to decode the video. I have FFDShow installed (which uses FFMpeg as a backend to decode VFW codecs) and I can successfully open your sample with this version. However, I recommend that you try FFMpegSource2 again. I have tried it on your sample and it works fine. Maybe try the latest version: http://code.google.com/p/ffmpegsource .

I use FFMpegSource2 for almost everything except AVI and ProRes Quicktime movies.


Sun, 2012/07/22 6:00 pm
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