Blocky Artifacts On iPod...

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voxsola
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Blocky Artifacts On iPod...

Post by voxsola » Sun Feb 18, 2007 4:32 am

This has always been an "issue" with me, I've just been putting up with it but now with MediaFork 0.8.0b1 I thought I'd ask about it again... see if anyone else still notices it or has had better luck getting rid of it.

I ripped Season 1 of Supernatural which tends to be a bit on the dark side using a video bitrate of 900 kbps and audio bitrate of 128 kbps, resolution of 368x208. MediaFork was much superior to Handbrake on my PowerBook G4 in terms of speed... I like it!

However I still notice a lot of blocky artifacts and gradients particularly in darker areas when playing the files on my 80GB iPod. Has anyone ever found a way to beat this? Would it help to raise the video bitrate and or resolution higher? The funny thing is every now and then I've had some files converted from .avi to .mp4 in iSquint that for some reason hit a "sweet" spot and showed hardly any artifacts/blocks and then other files... ??? not so good. So I can't put my finger on it... :?

baggss
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Post by baggss » Sun Feb 18, 2007 5:14 am

Try upping the video bitrate to 1500 and the video size to 640x480 and see what happens. This may boil down to a a choice between size and quality when deciding what you are willing to put up with. It's an issue with both HB and MF.

IIRC this has to do with a flaw in Quicktime which MF relies on. I know there is an explanation as to why iSquint doesn't have this issue, but I don't remember what it is to be honest.

voxsola
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Post by voxsola » Sun Feb 18, 2007 5:40 am

Thanks... I will give that a try on a particulary bad episode tonight... I'm interested in files for my iPod however if it does make a distinct difference then it may be worth to me for some things. I remember hearing something about Quicktime as well, to do with .mp4 and gamma I think?

I'll let you know how it turns out... :)

voxsola
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Post by voxsola » Mon Feb 19, 2007 2:10 am

Well... I tried using settings of 624x352 at 1500kbps on 2 of the most troublesome episodes and there was an improvement that might be worth it to me for my favourite TV show if it weren't for a couple of things...

1. It takes 6hrs. to do one 44min. episode on my PB G4 1.5GHz... for that much time I'd have to see a more marked improvement I think.
2. One of the episodes had some "skips" in it playing on the iPod... not in Quicktime or iTunes, just on the iPod.

But it's the 6hrs. per ep. that really turns me off so until I get a faster machine I think I'll settle for something more reasonable... :)

How do the videos purchased through the iTunes store compare for these issues? I can't see one being in Canada.

baggss
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Post by baggss » Mon Feb 19, 2007 3:32 am

I purchased TV shows, but no Movies. They occasionally have the blocky artifacts issue, but it's nothing I can't live with.

voxsola
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Post by voxsola » Mon Feb 19, 2007 5:02 am

OK... thanks.

Just wondered if they were generally about the same or not. Since they charge for them... ;)

dynaflash
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Re: Blocky Artifacts On iPod...

Post by dynaflash » Mon Feb 19, 2007 3:05 pm

voxsola wrote:I ripped Season 1 of Supernatural which tends to be a bit on the dark side using a video bitrate of 900 kbps and audio bitrate of 128 kbps, resolution of 368x208.
voxsola: you should be able to get pretty nice iPod only output using 360 x (xxx) the native iPod screen width. I would try one at 900-1000 at 360 width instead of 368 and see what you get. 368 would be a less than ideal size for the iPod to downscale to 360.

Also, I didnt see whether or not you were using h.264 or mpeg-4. It has been my experience that h.264 does better with the especially dark scenes and blockiness.

voxsola
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Post by voxsola » Mon Feb 19, 2007 10:04 pm

Yes, definitely... H.264 and 2-pass.

So you think the native 320x176 but just the higher bitrate? I'll give that a try... I've found that it looks better if ones watches these things with the iPod's widescreen turned Off although I'd rather not do that.

My reasoning for making them somewhat bigger was just "in case" I want to use them on a TV sometime and with a thought in mind to future iPods but then ??? who knows... faulty thinking? The "TV" would not be a huge new Plasma screen anyway.

baggss
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Post by baggss » Mon Feb 19, 2007 10:23 pm

Surprisingly, even stuff that I ripped with HB, 320x240 750k looks pretty darn good on a 42 inch plasma screen.

voxsola
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Post by voxsola » Mon Feb 19, 2007 10:52 pm

*lol** Well... at the moment I've got a 27" 15 year old Sony that still works so well... it's just not a priority with me. I'd rather have a new computer... ;)

When it eventually does break completely I'll see what I end up with...

hawkman
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Post by hawkman » Tue Feb 20, 2007 4:12 pm

A couple of things worth noting -

1. The iPod's screen does not display a full range of colours (compared to your Mac) - only in the thousands, I believe. It's possible this is contributing.

2. Blockiness, when observed during non-motion-heavy scenes, is generally the preserve of H.264 in my experience. Mpeg4 tends to be blocky only in high motion scenes (if the bitrate's too low); the main problem with it tends to be a jpg-esque halo around solid borders.

I notice you're using a very high bitrate for videos with fairly small resolution; it might be worth trying mpeg4, as I would think the bitrate will be high enough to make any worries about over-compression go away, and you might just avoid the blockiness.

voxsola
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Post by voxsola » Wed Feb 21, 2007 4:23 am

I tried an episode using Mpeg4 instead of H.264 and unfortunately it looked just as bad... I thought I'd try the same settings for resolution at 368x208 and left the audio at 128... but bumped the video bitrate a bit up to 1500kbps. Also I used HandBrake-0.7.1a2-UB because I've been having some trouble with "skipping" with MediaFork so thought I'd work on one thing at a time... ;) The resulting file only came out with a video bitrate of 560kbps though... :?

HB didn't respect my setting of 1500kbps which I think should have been plenty high enough to make a difference if it was going to. Why?

voxsola
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Joined: Sat Jan 06, 2007 10:13 pm

Post by voxsola » Thu Feb 22, 2007 11:45 pm

Well, I've hit on a happy medium for now I suppose... it seems it's still an ongoing issue with Apple/iPod/H.264... some combination, whatever.

I still have a problem with MediaFork "skipping" on some files. Just for a few seconds the video will "stutter"... it seems less likely to happen if I use the default 320x??? resolution. Anything over that and it happens. But MediaFork is so much faster that HB with wonderful results!

As far as the blockiness goes... I don't know why I never tried this before but it's one way to cut down on it quite dramatically I found on files that are particularly bad... set the iPod's widescreen to OFF and watch that file in full screen. If it's a TV episode it's quite acceptable and the reduction on artifacts is amazing... :)

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