x264 Lossless question

[stpdrgstr]

Hi, good day.

I was wondering if is safe to use x264 lossless, and is comparable to Lagarith.

I mean, if I reencode this x264 lossless to x264 lossy, it's the same as to reencode a Lagarith to a x264 lossy?

And, should I be using CoreAVC or libavcodec to decode this lossless through DSS2()?

These question had been retaining my sleep these days, so I would be very gratefull if they could be answered

Thanks.

[Dark Shikari]

x264 lossless has pretty much strictly superior compression to Lagarith, even in intra-only mode IIRC.

Unlike Lagarith, it only supports the YV12 colorspace.

To decode it correctly, you need a libavcodec from within the past ~2-3 weeks (as that's when support was added) or CoreAVC 1.8.5.

[Atak_Snajpera]

How to encode to lossless?

[J_Darnley]

Atak_Snajpera, huh? --qp 0 is that what you mean?

stpdrgstr, lossless is lossless, the input to "x264 lossy" in both cases should be the same.

[Atak_Snajpera]

Huh? --qp 0 is that what you mean?

yep! I meant switch. Thanks

[stpdrgstr]

Thank you very much. Now I can keep encoding at ease

[LoRd_MuldeR]

Note that for frame-accurate access to H.264 streams (lossless or not) you should use DGAVCIndex/AVCSource() instead of DirectShow.

I'm not sure whether AVCSource() already has an updated libavcodec with support for x264 lossless mode though...

[Dark Shikari]

Originally Posted by LoRd_MuldeR

Note that for frame-accurate access to H.264 streams (lossless or not) you should use DGAVCIndex/AVCSource() instead of DirectShow.

Frame-accurate access should never be an issue with lossless regardless of the decoder being used... since you shouldn't be using B-frames with lossless, so there is no frame delay.

[LoRd_MuldeR]

Originally Posted by Dark Shikari

you shouldn't be using B-frames with lossless

Didn't know that. Why is it like that? And does x264 automatically set "--bframe 0" when "--qp 0" is used?

(Could check the sources, but I'm too lazy right now ^^)

[Dark Shikari]

Originally Posted by LoRd_MuldeR

Didn't know that. Why is it like that?

It always reduces compression.

Originally Posted by LoRd_MuldeR

And does x264 automatically set "--bframe 0" when "--qp 0" is used?

No, because x264 isn't designed to protect you from your own stupidity.

A warning might be useful though.

[LoRd_MuldeR]

Originally Posted by Dark Shikari

It always reduces compression.

With "always" you mean "B-Frames always reduce compression in lossless mode". Not in general. Right?

Originally Posted by Dark Shikari

No, because x264 isn't designed to protect you from your own stupidity.

[LoRd_MuldeR]

I created streams with x264's mode "predictive lossless" mode using P-Frames and even B-Frames (didn't know b-frames are bad for lossless) and CoreAVC as well as recent ffdshow do handle it properly.

[vmrsss]

so what's a sensible command line for lossless?

[Dark Shikari]

Originally Posted by vmrsss

so what's a sensible command line for lossless?

Ultra-fast: --subme 1 --no-cabac --partitions none --me dia

Normal: --subme 5 --partitions all

Slow: --subme 6 --8x8dct --partitions all --ref 2

Slower: --subme 8 --8x8dct --partitions all --ref 4 --me umh --mixed-refs

Slowest: --subme 8 --8x8dct --partitions all --ref 16 --me esa --mixed-refs

Note that no-cabac loses about 10-15% compression but massively speeds up playback. Other things that hurt compression the most are subme=0 (vs other values) and partitions=none.

[damian101]

Originally Posted by Dark Shikari

Ultra-fast: --subme 1 --no-cabac --partitions none --me dia

Normal: --subme 5 --partitions all

Slow: --subme 6 --8x8dct --partitions all --ref 2

Slower: --subme 8 --8x8dct --partitions all --ref 4 --me umh --mixed-refs

Slowest: --subme 8 --8x8dct --partitions all --ref 16 --me esa --mixed-refs

Note that no-cabac loses about 10-15% compression but massively speeds up playback. Other things that hurt compression the most are subme=0 (vs other values) and partitions=none.

--partitions all

is usually harmful on noisy camera content, especially with subme < 6

Also,

--8x8dct

should be default anyway with all presets except ultrafast.

[vucloutr]

no --subme 9 for Slowest ?
typo or is there actually something to it ?

[Dark Shikari]

Originally Posted by vucloutr

no --subme 9 for Slowest ?
typo or is there actually something to it ?

No B-frames, so it isn't as if there's any difference between 8 and 9...

[Daiz]

I've made some of my own tests regarding various lossless video formats, and found out that not only does lossless H.264 compress the best, it also provides the fastest playback speeds.

In the test I made a while back, I encoded the same 2000-frame clip from a DVD source to various lossless formats and then made a 2-pass encode with x264 from the various lossless files using simple AviSynth inputs. Processor used was Intel C2Q Q6600 @ 2.4 GHz.

These were the x264 encoding settings used for the lossless -> lossy encode:

x264.exe --pass 1 --stats ".stats" --progress -B 768 -b 16 -r 1 --me dia --progress --subme 1 --no-dct-decimate --partitions none --threads 6
x264.exe --pass 2 --stats ".stats" --progress -B 768 -b 16 -r 6 --mixed-refs --b-pyramid --weightb --me umh --subme 7 --merange 24 --bime --b-rdo -A all --8x8dct --threads 6 --trellis 2 --aq-strength 1.0

And these were the results:

Lossless H.264 (encoded with --no-cabac) - average 47.587 fps - DSS2() with CoreAVC
1st pass: 143.07 fps, 790.41 kb/s
2nd pass: 28.54 fps, 778.01 kb/s

Lossless H.264 (encoded with --no-cabac) - average 47.014 fps - DSS2() with CCCP 2008-01-24's ffdshow
1st pass: 136.90 fps, 790.41 kb/s
2nd pass: 28.38 fps, 778.01 kb/s

Lossless H.264 (encoded with --no-cabac) - average 45.901 fps - FFMPEGSource()
1st pass: 133.39 fps, 790.41 kb/s
2nd pass: 27.72 fps, 778.01 kb/s

Lossless H.264 (encoded with --no-cabac) - average 45.250 fps - DirectShowSource() with CoreAVC
1st pass: 128.94 fps, 790.41 kb/s
2nd pass: 27.44 fps, 778.01 kb/s

FFVHuffy - average 42.722 fps - AVISource()
1st pass: 109.81 fps, 789.82 kb/s
2nd pass: 26.52 fps, 777.78 kb/s

Lossless H.264 - average 40.713 fps - DirectShowSource() with CoreAVC
1st pass: 92.26 fps, 793.68 kb/s
2nd pass: 26.12 fps, 778.26 kb/s

HuffYUV - average 27.449 fps - AVISource()
1st pass: 35.19 fps, 792.69 kb/s
2nd pass: 22.50 fps, 779.06 kb/s

Lagarith - average 15.130 fps - AVISource()
1st pass: 12.61 fps, 792.69 kb/s
2nd pass: 18.91 fps, 779.06 kb/s

I've been using x264 for my lossless needs ever since

Edit: Fixed the averages.

[Dark Shikari]

Note the proper way to average "20fps" and "100fps" is to do 2/(((1/20)+(1/100))), not just average the FPS (since the computer spends more time doing the 20fps encoding than the 100fps, so the average has to be weighted).

[Selur]

Just to be on the save side I ask: (otherwise I know there would be a thread in a not to distant future where Dark Shikari writes something like: "How people come to such assumtions ..."

Are there any other options aside form b-frame related once and "-nr" that should be (need to be) disabled when aiming for a lossless encode?

Cu Selur