Quick Sync vs Software File Sizes

[Designer_Bob]

Hello all.

I have been doing some test to see how speed and file size change when using either software or Quick Sync Encoding. Surprised with the results and confused.

The conversions using Quick Sync take half the time to encode, that's okay, but the files are much smaller? That I don't understand. Example. Using a bluray ISO image. Encoding to H264 1280 x 720 With AC3 audio

Desktop computer running Xeon E31280. All encoding settings on software. Lightning recode and shrink off. Using a CRF value of 17. End file size 3.32gb

Same settings on laptop with i7 3517u. All settings using quick sync with lightning recode and shrink on. Using CRF value of 17. End file size 2.53gb

Did the same test again using a CRF value of 16. Software only was 4.83gb vs Quicksync and lightning version 2.95gb

Why are the Quicksync versions smaller in size. The video quality looks just the same?

[signals]

I would suggest as a first step that you analyze the output files with MediaInfo and look for differences (and post the results here). One of the developers could probably answer this, especially with the help of the MediaInfo files.

[Designer_Bob]

Sorry should have included this information in the first posting; One of the main differences is that the software version has a much higher bitrate, even though they were both using a CRF value of 16. Other difference is Quicksync version using 2 ref frames.

I have tried to edit the profile information to increase the ref frames for the software version but for some reason it never goes above 1

Here is all the Media Info for the version encoded using QuickSync. Took only 6mins (not complaining there)

General
Complete name : C:\CF16 QS.mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 2.95 GiB
Duration : 1h 12mn
Overall bit rate : 5 846 Kbps
Movie name : CF16 QS
Album : BWE_S1_D1
Encoded date : UTC 2014-08-26 07:09:36
Tagged date : UTC 2014-08-26 07:14:32
Writing application : DVDFab 9.1.6.4
Cover : Yes

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L3.1
Format settings, CABAC : Yes
Format settings, ReFrames : 2 frames
Format settings, GOP : M=1, N=24
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1h 12mn
Bit rate : 5 524 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.250
Stream size : 2.79 GiB (94%)
Encoded date : UTC 2014-08-26 07:09:36
Tagged date : UTC 2014-08-26 07:14:32
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : ac-3
Duration : 1h 12mn
Bit rate mode : Constant
Bit rate : 320 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 166 MiB (5%)
Language : English
Encoded date : UTC 2014-08-26 07:09:36
Tagged date : UTC 2014-08-26 07:14:31

Menu
ID : 3
Codec ID : text
Duration : 1h 12mn
Encoded date : UTC 2014-08-26 07:09:36
Tagged date : UTC 2014-08-26 07:14:32
Bit rate mode : CBR

And here is all the MediaInfo for the file created using software only. This one took 25mins on the Xeon based machine.

General
Complete name : E:\CF16.mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 4.83 GiB
Duration : 1h 12mn
Overall bit rate : 9 560 Kbps
Movie name : CF16
Album : BWE_S1_D1
Encoded date : UTC 2014-08-26 05:36:21
Tagged date : UTC 2014-08-26 06:07:26
Writing application : DVDFab 9.1.6.4
Cover : Yes

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L3.1
Format settings, CABAC : Yes
Format settings, ReFrames : 1 frame
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1h 12mn
Bit rate : 9 236 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.418
Stream size : 4.67 GiB (97%)
Writing library : x264 core 142
Encoding settings : cabac=1 / ref=1 / deblock=1:0:0 / analyse=0x1:0x111 / me=umh / subme=6 / psy=0 / mixed_ref=0 / me_range=12 / chroma_me=1 / trellis=0 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=8 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=24 / keyint_min=13 / scenecut=40 / intra_refresh=0 / rc=crf / mbtree=0 / crf=16.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Encoded date : UTC 2014-08-26 05:36:21
Tagged date : UTC 2014-08-26 06:07:25
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : ac-3
Duration : 1h 12mn
Bit rate mode : Constant
Bit rate : 320 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 166 MiB (3%)
Language : English
Encoded date : UTC 2014-08-26 05:36:21
Tagged date : UTC 2014-08-26 06:07:21

Menu
ID : 3
Codec ID : text
Duration : 1h 12mn
Encoded date : UTC 2014-08-26 05:36:21
Tagged date : UTC 2014-08-26 06:07:25
Bit rate mode : CBR

[Designer_Bob]

Just a little addition.

Did the encoding again on my laptop but this time disabled all GPU codecs and disabled any lightning so that it was the same settings as my Xeon desktop machine.

The encoding took a little over 2 hours (in comparison to 6 mins using Quicksync and Lightning) but the file size was 4.83GB Identical to that on the Xeon.

Media Info shows the same results as the Xeon version - higher bitrate and only 1 ref frame. Does Quicksync limit the max bitrate?

[lixichen]

Quick Sync vs Software File Sizes

Hi, Designer_Bob

1. When use crf, the output file size is unpredictable.
In h264 encode, crf and biterate rate control parameters are mutually exclusive.
2. IQSV crf is not as good as Soft X264 encode,
software can do better control in each frame than hardware,
but IQSV output is still good enough for video play on big TV.
Quality : Soft crf > soft bitrate ≈ IQSV crf > IQSV bitrate.