MPEG3DEC/DGIndex and the YUY-Colorspaces

[krieger2005]

Hi,

i'm just wonder why all people cry to not convert the colorspace from YV12 and back to YUY2 but dgindex.dll and mpeg2dex3.dll, filters which are used every time for encoding DVDs just do this.

As i know the MPEG2-Stream of DVDs is coded in YUY2-Colorspace. When using the simple "mpeg2source(...)" one get a stream in YV12-Colorspace. When you want to re-encode a DVD and use avisynth with mpeg2source you take the YUY2-Stream of the DVD, convert it to YV12 (by using mpeg2source) and then you must convert it to YUY2 for the encoder?

Why? I know, that the old mpeg2dec2.dll supported YUY2-output. And the new one? I read somewhere of the "upConv"-Flag. Do this Flag just what i am described above... it take the "real"-YUY2-Stream of the MPEG2-Stream and support it? But why should one use this Flag only if the image is progressive?

I know that this all things are answered in several different threads... but it confusing me so i just call here for a answer.

krieger2005

[Guest]

DVDs are encoded with 4:2:0 sampling, which is equivalent to YV12. DGDecode will not upconvert this to YUY2 unless you ask it to by specifying upConv=true, which upsamples all pictures but chooses between progressive and interlaced upsampling based on the picture's progressive_frame flag. If you prefer all pictures to be upsampled as interlaced or progressive, you can use Avisynth's conversion function ConvertToYUY2().

[krieger2005]

Why use the Dvd-Rebuilder the "ConvertToYUY2"-Command on the End? If DVD's where compressed in YV12-Colorspace? What do the compressor internal? Do the convert from YUY2-Clip, which the avisynth-Script deliver, back to a YV12-DVD-Stream?

All this things are simply strange for me... Just after now about two years (or more) of encoding different types of video.


--
EDIT:
--
Just found the answer of my question here (http://forum.doom9.org/showthread.php?t=37276). This is simply stupid... however, thanks for your answer neuron2.

[Guest]

This is simply stupid... What is stupid? Doing ConvertToYUY2 in DVD Rebuilder?

I can't tell you anything about DVD Rebuilder. A script will serve the YV12 if you do not convert to YUY2. If you then encode in (say) VirtualDub using Fast Recompress to a YV12 output format, there will be no color space conversion along the chain.

[krieger2005]

No, sorry for the short description of that what i mean. I mean, that it is stupid, that you handle the video in Avisynth with YV12-Colorspace, must then convert it to YUY2 because the MPEG-Compressor want a YUY2-Colorspace and the Compressor itself convert it back to YV12.

I mean that way themself is stupid...

[Wilbert]

I mean, that it is stupid, that you handle the video in Avisynth with YV12-Colorspace, must then convert it to YUY2 because the MPEG-Compressor want a YUY2-Colorspace and the Compressor itself convert it back to YV12.
Use QuEnc to avoid this.