h264 compression question

[rsquires]

This is a question for those with video experience

-I am trying to recompress an animated sequence in QTpro, using h264.

The sequence is made of black lines on a 100% white background.
When I recompress using QT pro, h264, the background becomes slightly gray.

Is this a side effect of using this compression method on white ?
Does anyone have some advice how to deal with this?

thanks.

There is a documented problem with H264 encoding and it is one of the resons I don't use it. There is a noticeable gamma shift when you look at the compressed output next to your original. However drag the movie into Firefox or Safari and it plays ok. Just plain weird.

Check out this link for more info.

http://lists.apple.com/archives/QuickTime-Users/2006/Jul/msg00007.html

It depends on what you are trying to do but I find Sorenson 3 to be really capable of good to great quality with tiny file sizes.

regards

rich

[LucentDreams]

as i understand form that persons post, its specifically linked to macs using OSX versions that have core graphics as Core is changing the gamma, so its nothing to do with the codec or bad encoding, but soley on the way the mac is playing it back int he quicktime player. If you used a media player that doesn't use core or view on PC it seems it should be fine. You'd think they'd have a setting somewhere to tell core not to do that.

[moka.studio]

thanks for the info guys.
I thought it was maybe something to do with the gamma settings......
This will not be on a website, it will be for shown during a live presentation, so
don|t need the compression for the final material.

However i need to find a solution for sharing the file for comments etc..
maybe as Rsquires suggests, using another codec.

I will see if I find a good workaround

[StructAural]

A comment I found on one of those links.

'I [experienced] also an extreme color change problem by exporting Movies to H.264 Format. I found this solution to solve the problem:
Open the Filters in the Export Option and select Colour Sync in the Correction Section. For source profile choice your own Display Profile (Cinema HD) and for the Aim Profile choice Apple RGB.
The third Option didn't changed anything in my Results.
To see the Output before compression its necessary expand the little preview on the left down side by scaling the window layout.
You could also experiment with different Output Profiles.
Sometimes it makes sense - mostly not.'

[Activator]

I was also noticing that H.264 compressed footage looked a little washed out... I had compensated by lowering the brightness slider -5, and increasing the contrast +15 in the QuickTime Filters/Correction settings.

I tried changing the ColorSync settings output target as Apple RGB, and it looks much better.

In my opinion, H.264 compresses motion graphic footage SO much cleaner than Sorenson.

With H.264, I'm able to compress a 1/2 sized HD (640x320) 25 second spot from 328MB to 15MB with almost NO loss in quality. I wouldn't use it for On-Air, but for my clients appreciate the smaller download, and the quality is amazing.

[velarde]

Hi:

Actually this subject also came up a few days ago in the Electric Image forum.

http://forums.cgsociety.org/showthread.php?f=186&t=327725

Looks like this work around helps.

Good luck.

fjv

[Oli4D]

This is a question for those with video experience

-I am trying to recompress an animated sequence in QTpro, using h264.

The sequence is made of black lines on a 100% white background.
When I recompress using QT pro, h264, the background becomes slightly gray.

Is this a side effect of using this compression method on white ?
Does anyone have some advice how to deal with this?

thanks.

Have you tried to render out uncompressed images out of Cinema4D and then doing the Import and saving as H264 Movie out ouf QuickTime Pro?
That usualy workes better.
Saving a H264 directly in Cinema4D has the same weird Gamma Effect here.
But when I render out single images and then create the movie in QuickTime Pro, it usually works.

[moka.studio]

Have you tried to render out uncompressed images out of Cinema4D and then doing the Import and saving as H264 Movie out ouf QuickTime Pro?
That usualy workes better.
Saving a H264 directly in Cinema4D has the same weird Gamma Effect here.
But when I render out single images and then create the movie in QuickTime Pro, it usually works.\

hI Oli,
I always render frames.
I compressed using QT pro.
I never really noticed this issue, but on this project it is very noticeable since it is supposed to be a pure white background.
I am on PC by the way.

[Oli4D]

\

hI Oli,
I always render frames.
I compressed using QT pro.
I never really noticed this issue, but on this project it is very noticeable since it is supposed to be a pure white background.
I am on PC by the way.

Hey! I just tested it. I have the same issue (Win XP User) when the Background is pure white. Seems to be a QuickTime Pro Bug, or Codec Bug.
:-(

[NWoolridge]

As others have noted, this probably relates to Apple's use of Colorsync, and a mismatch between the monitor calibration and display color space. I'm not sure how Apple implements Colorsync on Windows, but it is potentially there (since Safari on Windows uses Colorsync to match web images...). Didn't Apple used to distribute a version of Colorsync for Windows...?

I wonder whether it might have to do with broadcast legal colors as well, since pure white is not legal in the NTSC color space...

Before exporting in QT player, you could try adding a Colorsync filter, if that is an option in Windows. Here's what it looks like on a Mac:

Nick

[LucentDreams]

Hey! I just tested it. I have the same issue (Win XP User) when the Background is pure white. Seems to be a QuickTime Pro Bug, or Codec Bug.
:-(
hmmm you know I just checked some cinversity videos, since the title cards have white and its all h264 now, and your right even the PC ones seem to have the problem, sadly I'm even viewing them through firefox.

[AdamT]

I've notice this on Windows too. I don't use h.264 because of it.

[govinda]

I think Kai's referring to this, which suggests that it's going to happen in both Windows and Mac, and that it's not h.264 itself that's the problem:

http://dvinfo.net/conf/showpost.php?p=525538&postcount=11

BluRay and HD DVD are still using h.264 full speed ahead, no? So you know h.264 isn't the culprit. But of course the matter of fault is trivial for people like us, because no matter the blame, it's still a problem that doesn't happen with Sorenson or other compression methods. Until it gets fixed (and Apple at least is aware of it, no mentioin of MS), this hurts, because Sorenson is slower and more complicated to compress for good results and file size, though equal results are pretty much possible from what I've seen.

[LucentDreams]

I dunno I'm still confused, for the mac guys its supposed to be okay in the webbrowser and not in quicktime itself, but I got curious as to why I never noticed this before in the cinversity videos, and quickly discovered why, mine is the exact opposite, only in the webrowser is it wrong for me, both media player classic AND QTpro opent he movie with the right gamma. wonder why mine is backwards

[moka.studio]

Hi:

Actually this subject also came up a few days ago in the Electric Image forum.

http://forums.cgsociety.org/showthread.php?f=186&t=327725

Looks like this work around helps.

Good luck.

fjv

Thanks for the link Velarde, this fixes the problem

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