FORUMS: list search recent posts

Random compression artifact in MC H.264

COW Forums : Compression Techniques

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Steve Brame
Random compression artifact in MC H.264
on Jun 11, 2009 at 2:10:15 pm

We are transcoding VOB files to H.264(MainConcept)using Squeeze, and we can't seem to get rid of some random artifact. It looks sort of like blocking that you'd expect to see in a low bitrate transcode during a dissolve transition, but they happen away from a dissolve. I've got a short sample up. The best examples of the blur happen at 10 and 20 seconds.

Here's the clip...

http://www.psidiscslaureate.com/675D/675D_intro/test.html

Our current Squeeze settings are...

532Kbps
Multi-Pass
Frame Rate 1:1 (29.97)
Key Frame Every 300 frames
Auto key frame on scene change
AVC Profile - High
Interlace Mode - Progressive
Encoding Effort - Best
B-Frames - 2
CABAC - yes
Slices - 3

If anyone could take a look at this clip and offer advice, I'd sure appreciate it.



Steve Brame
creative illusions Productions
VODSouth


Return to posts index

Daniel Low
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 3:05:43 pm

What frame size are you using - it looks a bit odd to me?

__________________________________________________________________
Two years from now, spam will be solved. - Bill Gates, World Economic Forum 2004


Return to posts index

Steve Brame
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 3:23:36 pm

They're at 480 x 360 per client specs.

Steve Brame
creative illusions Productions
VODSouth


Return to posts index


Steve Brame
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 3:26:35 pm

Some cropping is necessary, but I've got it set to maintain source aspect ratio.

Steve Brame
creative illusions Productions
VODSouth


Return to posts index

Daniel Low
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 3:34:31 pm

I measured the window on the test page and it's more like 508x380

__________________________________________________________________
Two years from now, spam will be solved. - Bill Gates, World Economic Forum 2004


Return to posts index

Steve Brame
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 3:48:40 pm

Sorry...thought you meant what size the video was transcoded to...not the player size. However, the player size isn't the problem. I'm playing locally in QT at the video's full size, and the problem still occurs.

Steve Brame
creative illusions Productions
VODSouth


Return to posts index


Daniel Low
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 4:36:23 pm

Try setting keyframes to every 150 - the nastiest bit of corruption appears at the very end of the clip everything else I saw was slight.

Try and avoid blue backgrounds on graphics!

And IMHO, never use the player to resize the frame - encode to the desired frame size.

__________________________________________________________________
Two years from now, spam will be solved. - Bill Gates, World Economic Forum 2004


Return to posts index

Steve Brame
Re: Random compression artifact in MC H.264
on Jun 11, 2009 at 5:35:08 pm

Unfortunately, I'm transcoding DVD's for which there are no original source files to alter the graphics with, so the blue must remain. I think my second issue is that I'm compressing a compressed file, which can generally lead to problems in itself. I've been trying different settings this morning, and I seem to get the best results when I turn off 'Auto Key Frame on Scene Change'. I'm thinking that something is making Squeeze think there's a scene change where there isn't one, and it's dropping in a key frame at that point.

If I set the player's dimensions to that of the video, I get black bars on the sides. That's why I changed the dimensions of the player...I merely reduced the dimensions until the black bars were gone. These bars are not a result of not cropping them out on transcode...those normal black bars are removed at transcode.

Steve Brame
creative illusions Productions
VODSouth


Return to posts index

Daniel Low
Re: andom compression artifact in MC H.264
on Jun 11, 2009 at 7:03:32 pm

Compressing heavily compressed stuff is never a good idea but it's unavoidable in your case so you have to make the best of it.
Sorenson doesn't actually know what 'scene changes' are only that when the differences between frames is above a certain threshold it will add a keyframe. Adding confusion to this calculation is also the placement of I B & P frames in the source MPEG-2.
As for frame size and player size, I'm not sure where you are going wrong by the bottom line is that the player video window (excluding the timeline) should exactly match the encoded video frame size. You should not be getting any black bars if done correctly.
Scaling using the player will impact the quality and playback performance.

__________________________________________________________________
Two years from now, spam will be solved. - Bill Gates, World Economic Forum 2004


Return to posts index


Steve Brame
Re: andom compression artifact in MC H.264
on Jun 11, 2009 at 7:54:20 pm

Take a look at the page now. I 'm using the JW Player, and I've got it's dimensions set to 480 x 360...the exact dimensions of the video frame size. Black bars on both sides.

Steve Brame
creative illusions Productions
VODSouth


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]