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Old 13th September 2002, 14:25   #1  |  Link
ScrollLock
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DV decoder differences

Hi folks,

since I recently purchased a DV device, I played around with various DV decoders. While I initially thought that they will all deliver the same result, I was surprised to find out that there is quite some significant difference between the decoders.


Canopus DV Codec V1.00

This codec uses the FourCC "cdvc", so before the system will use it you have to change the FourCC of the AVI file with a tool like AviC supplied with the XviD codec (default FourCC for DV is "dvsd").

Out of all DV codecs, the Canopus decoder does not seem to apply any sharpening of the decoded image (which is good in my opinion). It supports YUV2 and RGB color space.

Watch out though, when the Canopus decoder performs the RGB conversion it seems to use a luminance range of 16-235 instead of 0-255 used normally for computers.

RGB: http://mywebpage.netscape.com/wlopen...anopus_RGB.png [616 KB]
YUV2: http://mywebpage.netscape.com/wlopen...nopus_YUV2.png [557 KB]

A big issue with this decoder is that it has a nasty "chroma upsampling bug". This bug exists for both YUV2 and RGB. Fortunately this bug can be fixed using AVISynth's function "FixBrokenChromaUpsampling".

RBG with bug: http://mywebpage.netscape.com/wlopen...anopus_RGB.png [717 KB]
YUV2 with bug: http://mywebpage.netscape.com/wlopen...nopus_YUV2.png [776 KB]
YUV2 fixed: http://mywebpage.netscape.com/wlopen...YUV2_fixed.png [764 KB]


MainConcept DV Codec Demo V2.0.4

The MainConcept decoder supports both YUV2 and RGB. Unfortunately out of the 3 decoders it performs the most sharpening, which increases the noise level. In both RGB and YUV2 modes it uses a luminance range of 0-255.

RGB: http://mywebpage.netscape.com/wlopen...oncept_RGB.png [743 KB]
YUV2: http://mywebpage.netscape.com/wlopen...ncept_YUV2.png [716 KB]

The MainConcept decoder does not have the chroma upsampling bug:

RGB: http://mywebpage.netscape.com/wlopen...oncept_RGB.png [768 KB]
YUV2: http://mywebpage.netscape.com/wlopen...ncept_YUV2.png [824 KB]


Panasonic DV decoder (version unknown)

The Panasonic decoder supports RGB color space only. It sharpens less than the MainConcept decoder but more than the Canopus. The luminance range is 0-255.

RGB: http://mywebpage.netscape.com/wlopen...asonic_RGB.png [664 KB]

The Panasonic decoder does not have the chroma upsampling bug:

RGB: http://mywebpage.netscape.com/wlopen...asonic_RGB.png [734 KB]


My conclusion:
For RBG color space (e.g. for VirtualDub) the Panasonic DV decoder is the preferred choice. The Canopus decoder can't be used for that application due to it's chroma upsampling bug, and is also not preferred due to the reduced luminance range.
For YUV2 (e.g. AVISynth) I use the Canopus decoder and use the "FixBrokenChromaUpsampling" function to correct it's bug.
The MainConcept decoder applies too much sharpening for my taste, but if your source is noise-free than this decoder might be your decoder of choice as it supports both YUV2 and RGB, and does not suffer from the chroma upsampling bug.


yours truely, ScrollLock


Addendum: measuring method
All screenshots were taken from the same frame of the same DV file. The source files, which were capture from cable TV in Singapore (PAL), can be found at:
Test signal: http://mywebpage.netscape.com/wlopen...TestSignal.avi [308 KB] (2nd frame was used)
Chroma bug check: http://mywebpage.netscape.com/wlopen...e3300-3310.avi [604 KB] (4th frame was used)

For RGB decoding the files were directly opened in VirtualDub. For YUV2 the files were passed through AviSynth and then into VirtualDub.

No processing was done for the Test Signal samples. For the chroma bug samples the source was deinterlaced. For RGB the VirtualDub filter "deinterlace - area based" was used. "Blend instead of interpolate" was turned off, Threshold=27, Edge detect=25. For YUV2 the AVISynth filter GreedyHMA(0,0,1,0,0,0,0,0) was used.
NOTE: don't compare the image quality between RGB and YUV2 as it is influenced by the different deinterlace algorithms!

Last edited by bb; 20th August 2005 at 10:31.
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Old 13th September 2002, 14:48   #2  |  Link
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Fichtre ! (as we say in french), astonishing !
It's a long time since i havn't checked that chain link, and i thought i was OK using mainconcept...
As i want to test that, perhaps you could you help me:
The DV compression is done by the camcorder, and OHCI capturing is just a file transfert.
So can i change my captured avi files from one coded to an other, without re-writing or re-capturing ? (tests purpose, as i can't recapture right now).

.
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Old 13th September 2002, 15:09   #3  |  Link
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Quote:
Originally posted by taudule

The DV compression is done by the camcorder, and OHCI capturing is just a file transfert.
So can i change my captured avi files from one coded to an other, without re-writing or re-capturing ?
Absolutely! The encoding is not in your influence at all, it is done in hardware in your camcorder as you wrote correctly. "Capturing" from a DV camcorder is basically only dumping the content received from the camcorder via FireWire into an AVI file on your harddisk.

You can install the Canopus decoder in parallel with either the MainConcept or the Panasonic decoder as it uses a different "FourCC" code. But in order to use it, you have to change the FourCC of your captures from "dvsd" (= the standard in Windows, used by Pana and MainConcept) to "cdvc" (= Canopus proprietary). This can be done with various tools, e.g. with "AviC" supplied with the XviD MPEG4 codec.
Note that this only changes a few characters in the AVI file, it does not alter the actual A/V-data in any way.

I think that in order to switch between the Pana and the MainConcept, you have to uninstall the current one before installing the other, but maybe there are tools that allow you to select which decoder to be used for a given FourCC. Anybody knowledgable of such a tool?

salut, ScrollLock
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Old 13th September 2002, 15:45   #4  |  Link
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Thank you for your quick answer. i'll do some testing this WE.
I just made some research and found here :
http://www.canopus.com/US/products/D..._converter.asp
the (free) tool to convert the streams.
It rewrites the avi, but i suspect it is not necessary as you state; changing "dvsd" to "CDVC" in the avi header makes it seen as "canopus software DV" in the file properties box.
How can i be sure that when outputed to the screen, the avi is really uncompressed by canopus?
.
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Old 13th September 2002, 15:45   #5  |  Link
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First thing: amazing! Thanks!

Second thing: How can I prevent MS decoder from being used?

bira
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Old 13th September 2002, 16:02   #6  |  Link
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Quote:
Originally posted by taudule

How can i be sure that when outputed to the screen, the avi is really uncompressed by canopus?
Open the file in VirtualDub, go to the file menu and select "File Information". The dialog that comes up shows you the used compressor.

Quote:
Originally posted by bira

How can I prevent MS decoder from being used?
No idea. Actually, I don't know at all how to use the MS DV decoder in the first place in AVISynth or VirtualDub. Even when I use "DirectShowSource" in AVISynth it used the Canopus/MainConcept/Panasonic decoder (depending on what was installed and what the FourCC said).
Hopefully someone else will give us a satisfying answer.
BTW: according to the AVISynth documentation, the MS codec also suffers from the chroma upsampling bug.

kind regards, ScrollLock
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Old 13th September 2002, 16:44   #7  |  Link
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Quote:
MainConcept DV Codec Demo V2.0.4

The MainConcept decoder supports both YUV2 and RGB. Unfortunately out of the 3 decoders it performs the most sharpening, which increases the noise level. In both RGB and YUV2 modes it uses a luminance range of 0-255.
You are perfectly right! I just finished viewing side by side with 2 virtualdubs the same DV source, one decoded by mainconcept, the other by canopus (via avisynth script), and the result is noticeably better with canopus (less noise). I'm now going to test encoding, but it should improve... I'm really surprised nobody noticed that before (i've read so many discussion about DV codecs already!).

BTW, changing the dvsd for CDVC in the avi header is enough to enable decoding by canopus, provided you have the canopus codec installed, of course (i use W2000)
.
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Old 13th September 2002, 17:33   #8  |  Link
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Quote:
Even when I use "DirectShowSource" in AVISynth it used the Canopus/MainConcept/Panasonic decoder (depending on what was installed and what the FourCC said).
Does that mean that if any other dv decoder is installed, MS decoder will never be used in any software?
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Old 14th September 2002, 00:56   #9  |  Link
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Quote:
Originally posted by bira


Does that mean that if any other dv decoder is installed, MS decoder will never be used in any software?
I have no idea, to be honest. It was just my (brief) observation, and possibly I did something wrong. Or maybe the MS DV codec uses another FourCC?

regards, ScrollLock
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Old 14th September 2002, 06:08   #10  |  Link
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What I've seen is that VirtualDub can not call/see the Microsoft codec because VirtualDub uses vfw rather than wdm screen drivers.

I have another programme called Multiquence which will see the Microsoft wdm based codec and use it. It turns out that Ulead's Video Studio also uses the MS codec. Mainconcept's codec is vfw based. So as long as you are using VirtualDub, you will not have to deal with the MS codec. But if you decide to used Graphedit, then you can and wil end up calling the MS codec.
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Old 15th September 2002, 11:34   #11  |  Link
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I guess the MS codec will be used if you frameserver through AviSynth using the "DirectShowSource" command.

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Old 15th September 2002, 16:48   #12  |  Link
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great thred

great thread scrollock , after reading and doing test i now how to get my dv avis to use the canpos decoder and i love it , its so much better then mainconpt

congrats

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Old 20th September 2002, 18:35   #13  |  Link
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DV Codec Swap

Great thread, thanks for your enlightening research, scrollock.

Maybe I can help with a link to a neat little codec swapping program:
Try VCSwap, which can be downloaded from
http://members.ams.chello.nl/p.bekke/
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Old 20th September 2002, 18:58   #14  |  Link
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This VC Codec swapper? A great find! Thank you.
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Old 4th October 2002, 17:00   #15  |  Link
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I just found that link in my archives, while making some dust clean :
http://home.hetnet.nl/~jackwburger/index.html

Happy codec swapping
O.
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Old 5th October 2002, 23:21   #16  |  Link
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While I am not 100% sure on this, but I remember reading about DV codecs and that Mainconcept and Canopus are different but Sony/Panasonic/Microsoft were actually the same. They differ by nothing that affects output, they put out the same output (S/P/M), while Canopus and Mainconcept do something else to quality.

If anyone knows more or heard of this, more info would be nice (besides what ScrollLock has mentioned from experience, I mean more of a technical side of it).
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Old 20th January 2003, 10:02   #17  |  Link
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Nice thread ScrollLock - ever done any tests with Fast's DV codec? (this is used in Pinnacle Edition, because the program is actually Fast DV Studio)

Canopus attempted to do a demolition job on the competitions' hardware cards by illustrating generational codec losses, BTW.


Arky ;o)
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Old 4th March 2003, 20:13   #18  |  Link
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Just to clarify a few points: installing a DV codec is only necessary for programs that only use video for windows (vfw) and type 2 avi DV files such as Vdub. If your program uses directshow (included in Direct X) and type 1 DV avi, it will automatically use the built-in MS DV codec. Vdub is a vfw only program. For vdub, a DV codec is necessary and you must use type 2 DV avi files. More and more programs are using directshow. So installing a DV codec is becoming less and less necessary (although it doesn't hurt to install one in case that you wish to use it for a type 2 DV avi file).

Microsoft explains all of this in the following text:

http://www.microsoft.com/hwdev/tech/...dcap/dvavi.asp

Adam Wilt also explains this on his website:

http://www.adamwilt.com/DV-FAQ-editing.html#NLE

See also this website:

http://www.well.com/user/richardl/Si...tFrameSet.html

In a simplified version, the Microsoft article states that a type 2 DV avi file is vfw compatible and that a type 1 DV avi file is not vfw compatible. Directshow can read both type 1 and type 2 DV avi files. In other words, a vfw only program (such as vdub) will not be able to read type 1 files. It will be able to read a type 2 file DV avi file if a DV codec is installed. A program that uses directshow (for example, Premiere 6.5 or Ulead VS 7.0) will not need a DV codec for a type 1 or a type 2 DV file (but a DV codec can be used for a type 2 DV avi file).

On an unrelated point, the Canopus DV codec only gets used for Canopus software (or if you convert the DV avi file to a Canopus DV file). For this reason, I have never actually used it. In order for vdub to accept type 2 DV avi files, I have installed the Panasonic DV codec.

Interestingly, it seems that Panasonic is making the MS DV codec that is built in directshow. See this link:
http://www.microsoft.com/presspass/p...97/MSMEIpr.asp

P.S. Incidentally, you can use the following freeware programs to capture in type 2 DV avi: DVapp or DVIO.

Last edited by yg1968; 5th March 2003 at 20:26.
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Old 5th March 2003, 07:30   #19  |  Link
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Quote:
Originally posted by yg1968
Vdub is a vfw only program. For vdub, a DV codec is necessary and you must use type 2 DV avi files.
Yes, indeed, VirtualDub is a VfW based program. But despite what you say it can open DV type-1 files. You'll get a warning, and you can't process the audio, but for video processing only simply open the type-1 file, ignore the warning, and use it just like any other AVI. You need a VfW DV codec installed, though.

By the way: it seems that not all type-1 and type-2 capable video editors work equally well with either format. E.g. Ulead's Media Studio Pro 6.5 is quite buggy when using type-2, but it seems to work fine with type-1. You'll experience the difference when using more complicated transitions / overlays.

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Old 5th March 2003, 14:04   #20  |  Link
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bb, on that note I would add that Vegas also has trouble with longer and more complicated output from the DV1 type files generated by WMM2. Short and simple ones seems ok. Using the free file convertor from Canopus and converting the file to MS DV2 seems to take care of the problem.
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