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TMPGEnc CRI Sofdec question

 
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royalbox



Joined: 12 May 2003
Posts: 39

PostPosted: Sat 19 Jul 2003, 15:08    Post subject: TMPGEnc CRI Sofdec question Reply with quote

@rmm
The 2.520 version of TMPGEnc update page says this:

Quote:
Includes the MPEG decoder CRI Sofdec. Now, input of MPEG-2 files is a standard feature. Plus, the picture quality (brightness, color) shown on your pc display will be close to the one on your TV. So the editing will be easier.
*when using CRI sofdec:
remove the check on [ Output YUV data as Basic YCbCr not CCIR601 ]
[ Setting ] => [ Quantize matrix ] => [Output YUV data as...]
*when using CRI sofdec, you can open a maximum of 8 sequence files as a movie.


If you're only encoding mpeg-2 from avi files, do you have to uncheck that box or leave it as your guide says? How do you know whether you're using CRI softdec or not?

Many thanks.
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Sat 19 Jul 2003, 17:29    Post subject: Reply with quote

As the text says, Softdec is a MPEG-2 decompressor, so when you're converting AVIs you're not using it (only when recompressing MPEG-2, ex., converting a DVD to SVCD).

The decision on whether you should output "straight" YCbCr or scale it to CCIR range depends on your (input) codec. In the case of DV codecs, you should usually disable the option for software codecs (ex., MainConcept) and enable it for hardware codecs (Sony, Canopus). This is due to the fact that most software codecs always scale the range for display on a VGA monitor, while hardware codecs preserve the original range, because they expect you to use a separate video monitor.

As that text suggests, the CRI MPEG-2 decompressor does rescale the values for display on the VGA monitor, so in that case the option should be disabled (to force TMPGEnc to convert back to CCIR range, so that it plays properly on TVs and video monitors).

RMN
~~~


Last edited by RMN on Sun 20 Jul 2003, 14:57; edited 1 time in total
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royalbox



Joined: 12 May 2003
Posts: 39

PostPosted: Sat 19 Jul 2003, 17:48    Post subject: Reply with quote

@rmn
Ok, I think I've got that, thank you. But what you have said has made me unsure about whether I'm using the right setting or not.

I am converting dv encoded with the mainconcept encoder you mentioned. So, would you say I should uncheck that option? Am I right in thinking this affects the contrast of the final DVD? My dvds do seem to have high contrast, but I put it down to the dvd player trying to make things look more 'impressive' or maybe the tv. Or, have I completely misunderstood what this is about? (quite likely).
Many thanks.
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Sun 20 Jul 2003, 14:57    Post subject: Reply with quote

I have used MainConcept's DV codec, but never with TMPGEnc, so I can't be 100% sure of this, but what I've heard from several people is that this codec does perform range scaling when it decompresses (so that the image on the PC screen looks a bit more like the TV). This is, IMO, a very, very stupid thing to do (it can cause loss of data, although normally it won't), but unfortunately it's common with software-only codecs.

If this is true, then enabling the "straight YCbCr" option will prevent TMPGEnc from scaling the values back to "video" range, which means the contrast in the final movie will be about 14% higher than it should. So you probably should turn it off to preserve the original contrast.

Of course, if you prefer the more contrasted look, leave it on. In the end, what matters is your (subjective) opinion.

RMN
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royalbox



Joined: 12 May 2003
Posts: 39

PostPosted: Sun 20 Jul 2003, 22:23    Post subject: Reply with quote

@rmn
Now you come to mention it, I think I read somewhere once that the mainconcept codec does 'something' to the video. I do find the dvds I've created to have too much contrast, but I put it down to the player as it looked good on the computer monitor, but now you've explained why that would be. I also have a panasonic dv codec that I downloaded somewhere or other some time ago but have never used. It used to be freely available on panasonic's own site but isn't any more. I may try using that instead. I'll certainly try my next compression with that option unchecked.
Many thanks for all your help, as always.
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