CUDA H.264 vs x264 Speed and Image Quality Benchmarks, discussion

[Manao]

If you wanna have x264 encode at the max speed too (as was the case on my system here), you might wanna go for sth like --bframes 0 --subme 5 and remove the --no-cabac. That caused no slowdown for me whatsoever in comparison to ultrafast's defaults.

You'd better keep bframes too. They usually reduce bitrate by 20% at the same quality (cabac is "only" 10%, deblocking is 10% also).

[St Devious]

Originally Posted by stanleyhuang

Hoping some people can free themselves from prejudices.

not sure what you mean. But I know that CPU encoding is where its at, and GPU encoding is still in its infancy and can't compete with x264 in its current form. When I see slides from Nvidia and ATI and review sites that GPU encoding is 5 times faster than CPU encoding and there is no mention of image quality, that makes me kinda angry.

So I'm just trying to provide proof.

Originally Posted by stanleyhuang

What I was thinking is that you are using a more advanced CPU and a less advanced GPU.

Not sure how you would measure that.

Originally Posted by stanleyhuang

BTW: I think you can use MediaCoder to do benchmark for both x264 and CUDA H.264 encoder. This will eliminate the difference in decoding.

That's a good idea but as in business they say, you can't make everyone happy, I fear I would get flamed for that too for trying to advertise mediacoder

[dj_tjerk]

Originally Posted by Manao

You'd better keep bframes too. They usually reduce bitrate by 20% at the same quality (cabac is "only" 10%, deblocking is 10% also).

Maybe so, but in my case --bframes 1 with --no-cabac and --subme 0 caused it to slow down to about 108 fps (whereas setting --bframes 0 and --subme 5 and removing --no-cabac caused no slowdown whatsoever from my maximum). So I got subme and cabac for "free".

St Devious however chose to set bframes 1 before changing anything else, eventhough with his goal of comparing quality at the same speed (i.e. maximum possible speed), he should've enabled cabac and subpixel refinements, since those would've most likely caused x264 to encode at the same speed as cuda (assuming his system behaves the same as mine does).

[St Devious]

Originally Posted by dj_tjerk

St Devious however chose to set bframes 1 before changing anything else, eventhough with his goal of comparing quality at the same speed (i.e. maximum possible speed), he should've enabled cabac and subpixel refinements, since those would've most likely caused x264 to encode at the same speed as cuda (assuming his system behaves the same as mine does).

I am under the impression that presets override any settings. is that the case ?

[LoRd_MuldeR]

Originally Posted by St Devious

I am under the impression that presets override any settings. is that the case ?

Nope. Presets don't overwrite anything! If a preset is selected, it is applied first. Then all explicit options are applied (and may overwrite what the preset has set).

In other words: Instead of starting from the defaults, we start from the selected preset. But that's all.

Maybe you are thinking of the new "--profile" option (which is applied after the explicit options). That option does overwrite your settings, as it enforces a certain level!

[St Devious]

Originally Posted by LoRd_MuldeR

Presets don't overwrite anything! If a preset is selected, it is applied first. Then all explicit options are applied (and may overwrite what the preset has set).

ok then I will try to set the same option as the preset ultrafast in the MeGUI x264 settings GUI

[stanleyhuang]

Originally Posted by St Devious

not sure what you mean.

I mean the people claiming that you intend to make these benchmarks to advertise something. I hope they can be a bit open-minded.

That's a good idea but as in business they say, you can't make everyone happy, I fear I would get flamed for that too for trying to advertise mediacoder

That's likely. ;-)
So every word should be neutral here.

[St Devious]

I'm comparing now with best quality that each encoder can provide at a certain bitrate.

Using this video

1080p VBR Video Quality Test Streams
Sony HDW-F900 footage, 1080p@25, 18 Mbps average, 30 Mbps peak in a 35 Mbps Transport Stream (259,534,064 bytes)

on this page http://www.w6rz.net/

Encoding both encoders to 4Mbps and 6 Mbps.

Using 2 pass unrestricted HQ profile in Megui, would extra quality provide some better quality ?

And here are the settings for CUDA encoder in Mediacoder. Please let me know what to set to compare to match x264

[stanleyhuang]

The CUDA H.264 encoder in current release doesn't support 2-pass mode yet.

[St Devious]

Originally Posted by stanleyhuang

The CUDA H.264 encoder in current release doesn't support 2-pass mode yet.

i meant used 2 pass unrestricted HQ for x264.

But How can i configure the CUDA encoder to provide maximum quality ?

Here is an update, click on the images to get full size 1920x1080 image

x264 @ 6 Mbps


CUDA @ 6 Mbps



Source


Mediainfo

Source

Video
ID                               : 49 (0x31)
Menu ID                          : 1 (0x1)
Format                           : MPEG Video
Format version                   : Version 2
Format profile                   : Main@High
Format settings, Matrix          : Default
Duration                         : 2mn 7s
Bit rate mode                    : Variable
Bit rate                         : 32.5 Mbps
Nominal bit rate                 : 30.0 Mbps
Width                            : 1 920 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 16/9
Frame rate                       : 25.000 fps
Colorimetry                      : 4:2:0
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.628
Stream size                      : 493 MiB (92%)

x264

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L5.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 5 frames
Codec ID                         : avc1
Codec ID/Info                    : Advanced Video Coding
Duration                         : 2mn 7s
Bit rate mode                    : Variable
Bit rate                         : 6 000 Kbps
Maximum bit rate                 : 16.6 Mbps
Width                            : 1 920 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 16/9
Frame rate mode                  : Constant
Frame rate                       : 25.000 fps
Resolution                       : 24 bits
Colorimetry                      : 4:2:0
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.116
Stream size                      : 90.9 MiB (100%)
Writing library                  : x264 core 68 r1179M 96e2229
Encoding settings                : cabac=1 / ref=5 / deblock=0:0:0 / analyse=0x3:0x133 / me=umh / subme=7 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / 
chroma_qp_offset=-2 / threads=6 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=2 / b_bias=0 / direct=3 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40 / rc=2pass / bitrate=6000 / ratetol=1.0 /
 qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00

CUDA

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L5.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 2 frames
Codec ID                         : avc1
Codec ID/Info                    : Advanced Video Coding
Duration                         : 2mn 7s
Bit rate mode                    : Variable
Bit rate                         : 6 035 Kbps
Maximum bit rate                 : 42.0 Mbps
Width                            : 1 920 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 4/3
Frame rate mode                  : Constant
Frame rate                       : 25.000 fps
Resolution                       : 24 bits
Colorimetry                      : 4:2:0
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.116
Stream size                      : 91.4 MiB (100%)

[Selur]

@St Devious: your x264 and your CUDA Screenshot link to the same picture,... (CUDA should be: http://www.picturepush.com/public/1958118)

[RunningSkittle]

Levels are different in the x264 image as well.

[St Devious]

Originally Posted by Selur

@St Devious: your x264 and your CUDA Screenshot link to the same picture,... (CUDA should be: http://www.picturepush.com/public/1958118)

thanks, corrected it now.

Originally Posted by RunningSkittle

Levels are different in the x264 image as well.

what do you mean ?

[LoRd_MuldeR]

Originally Posted by St Devious

what do you mean ?

He talks about luminance levels, I think!

http://forum.doom9.org/showthread.php?t=143689

But I'm not so sure whether this is a level problem, because the "black" intensity looks identical in both screenshots.
Typically you would get "black" vs. "dark gray" when comparing pictures of different luminance levels, but that's not the case here.
Looks more like something is wrong with the color intensities. Look at the red shirt and the cyan bag!

[buba king]

Originally Posted by St Devious

what do you mean ?

The colors are different in the x264 screen shot... probably a bad color conversion somewhere.

[St Devious]

MeGUI had me add ConvertToYV12() at the end of script, is that a problem ?

[LoRd_MuldeR]

Originally Posted by St Devious

MeGUI had me add ConvertToYV12() at the end of script, is that a problem ?

Nope. That's because x264 doesn't accept anything but YV12() data. But you should use the very same source script for both encoders

[St Devious]

Originally Posted by LoRd_MuldeR

Nope. That's because x264 doesn't accept anything but YV12() data. But you should use the very same source script for both encoders

hmm.. didn't think that way. Guess that may have invalidated the above images.

Will encode with an avisynth script when i get home tomm.

btw what about Stan's suggestion of using Mediacoder to encode with both CUDA and x264 ? that wa decoders should be the same.

[LoRd_MuldeR]

Originally Posted by St Devious

btw what about Stan's suggestion of using Mediacoder to encode with both CUDA and x264 ? that wa decoders should be the same.

Given that MediaCoder really uses the same decoders, processing and colorspace conversion for both encoders

I'd go with Avisynth to be 100% sure that the source data is identical for both encoders!

The less steps there are between your source and the encoder, the less things can corrupt your results.

Directly feeding the source into the encoder from Avisynth (using the identical script) is the most reliable method.

[St Devious]

Originally Posted by LoRd_MuldeR

Given that MediaCoder really uses the same decoders, processing and colorspace conversion for both encoders

I'd go with Avisynth to be 100% sure that the source data is identical for both encoders!

The less steps are between your source and the encoder, the less things can influence/corrupt your results.

Directly feeding the source into the encoder from Avisynth (using the identical script) is the most reliable method...

thanks.

How does the decoding happen ?

Like what will Mediacoder and MeGUI use to decode the avisynth file ?

And how does the avisynth file decode the .ts source file ?