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Old 3rd June 2008, 00:28   #1  |  Link
KornX
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h264 LOSSLESS experiences

if you do a 1080p24 encode with the lossless mode, what bitrates are we talking about (yeah i know, content...)
But what are your experiences?
And how many of you use it (at least sometimes)

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Old 6th June 2008, 19:29   #2  |  Link
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depends on what video you try to encode losslessly of course

so try it yourself on the for you relevant content
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Old 6th June 2008, 22:16   #3  |  Link
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Hi,

are you talking about perceptually lossless or really lossless (QP = 0)? In the latter case it's possible that you get data rates exceeding those of raw uncompressed YUV files, in the former case - of course depending on the content - you can expect some 20 to 50 MBits/s

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Old 6th June 2008, 22:18   #4  |  Link
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Quote:
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In the latter case it's possible that you get data rates exceeding those of raw uncompressed YUV files
This is extremely doubtful. I've only ever seen a single macroblock ever exceed its uncompressed size with lossless x264 encoding, and technically the standard requires that any such block be coded as I_PCM anyways.
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Old 6th June 2008, 22:27   #5  |  Link
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I wrote that it is possible and I experienced one such case myself when IPCM mode was accidently disabled. But anyways, using lossless mode makes no real sense to me because the bit rate required is extremely high and the difference to a file encoded with p.e. CRF 16 is perceptually zero.

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Old 6th June 2008, 22:30   #6  |  Link
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Quote:
Originally Posted by Dust Signs View Post
I wrote that it is possible and I experienced one such case myself when IPCM mode was accidently disabled.
x264 doesn't actually support I_PCM mode; its in the code right now but it isn't enabled.
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But anyways, using lossless mode makes no real sense to me because the bit rate required is extremely high and the difference to a file encoded with p.e. CRF 16 is perceptually zero.

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Its far better than most other lossless options in the case that inter prediction is very useful, such as for CGI or animated sources which were originally lossless.
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Old 6th June 2008, 22:33   #7  |  Link
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x264 doesn't actually support I_PCM mode; its in the code right now but it isn't enabled.
I wasn't talking about x264 concerning that matter - this time I was using a different encoder. Concerning CGI I agree with you, but I think many people are using "normal" video material (movies etc.) much more often.

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Last edited by Dust Signs; 6th June 2008 at 22:36.
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Old 11th June 2008, 23:32   #8  |  Link
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I'm doing my first lossles try right now. The source is a 01:31:20 old anime movie on DVD. It needs a lot of denoising, which I'm not doing right now. The lossles pass is only for AnimeIVTC. After 75% the projected filesize is of 12.8GB.

I'm using MeGUI's CQ-Lossless profile:
Code:
 --qp 0 --nf --subme 1 --partitions p8x8,b8x8,i4x4 --merange 12 --threads auto --thread-input --progress --no-psnr --no-ssim --output
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Old 11th June 2008, 23:45   #9  |  Link
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Originally Posted by elguaxo View Post
I'm doing my first lossles try right now. The source is a 01:31:20 old anime movie on DVD. It needs a lot of denoising, which I'm not doing right now. The lossles pass is only for AnimeIVTC. After 75% the projected filesize is of 12.8GB.

I'm using MeGUI's CQ-Lossless profile:
Code:
 --qp 0 --nf --subme 1 --partitions p8x8,b8x8,i4x4 --merange 12 --threads auto --thread-input --progress --no-psnr --no-ssim --output
Subme 1? That's a waste; most time is spent in bitstream encoding, so a higher subme hardly takes any more time (until you get to 6 or above, at least). --nf does nothing there, and --no-psnr and --no-ssim do nothing too. The partitions is what is used as default, and the --merange is silly with --me hex.
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Old 12th June 2008, 00:04   #10  |  Link
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This encode is almost done, but I will use subme 5 or 6 next time. What would be a good merange value if I keep --me hex? Thanks
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Old 12th June 2008, 00:07   #11  |  Link
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This encode is almost done, but I will use subme 5 or 6 next time. What would be a good merange value if I keep --me hex? Thanks
For hex, there's no reason to change it to anything but the default (16).
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Old 12th June 2008, 00:07   #12  |  Link
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Quote:
Originally Posted by elguaxo View Post
This encode is almost done, but I will use subme 5 or 6 next time. What would be a good merange value if I keep --me hex? Thanks
I think --merange does not apply to "hex" mode, only "umh" and higher...
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Old 12th June 2008, 00:13   #13  |  Link
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Originally Posted by LoRd_MuldeR View Post
I think --merange does not apply to "hex" mode, only "umh" and higher...
It does, its just that its clipped to 4<=X<=16.
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Old 12th June 2008, 00:15   #14  |  Link
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Old 12th June 2008, 00:21   #15  |  Link
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Quote:
Originally Posted by Dark Shikari View Post
It does, its just that its clipped to 4<=X<=16.
Sorry, I was mistaken
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Old 12th June 2008, 23:12   #16  |  Link
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If you want a lot more speed out of lossless, just turn cabac off. It'll be slightly larger but not as much as you'd expect. You lose a lot less efficiency than you do at low bitrates, since so many of the randomer high quantizers are present.
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Old 12th June 2008, 23:16   #17  |  Link
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Quote:
Originally Posted by foxyshadis View Post
If you want a lot more speed out of lossless, just turn cabac off. It'll be slightly larger but not as much as you'd expect. You lose a lot less efficiency than you do at low bitrates, since so many of the randomer high quantizers are present.
The benefit of CABAC in lossless is actually higher than at low quantizers:


(thanks to akupenguin for this chart)

But yes, overall, its definitely worth turning off given the very large speed boost one gets; (de|en)coding lossless is nearly pure entropy (de|en)coding.

Last edited by Dark Shikari; 13th June 2008 at 01:58.
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Old 13th June 2008, 01:58   #18  |  Link
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Oh wow, that's crazy, thanks for letting me know. I normally use might-as-well-be-lossless qp 1 or 2, so I assumed behavior would translate over, good to know the truth.
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