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View Full Version : UHD file size is tiny - can that be ?


blublub
4th November 2018, 09:25
Hi

I just recently converted most of my Blurays to x265 (from source) and the bitrate ended up somewhere from 7 to 10mbits for video only - that was about a 20% reduction on average compared to the older x264 files.

So yesterday I did two encodes of a UHD HDR BluRay and the final file sizes puzzled me (video only presented here):

File 1:
lenght 2h 20m
Bitrate 4400
size 4,3gb

File 2:
length 2h 3m
Bitrate 14600
Size 12,5gb

Since UHD has 4x!? times the pixels of 1080p I was expecting a bitrate of around 20mbits since the original source files also had a bitrate of 45+ mbits - I was not prepared to such a reduction in file size.

My encoding settings where of course a little different with the main difference being CTU size 32 for 1080p, qcomp=0,63 and default for the UHD encodes (shown below).

I know that I am somehow comparing apples and oranges here - so the questions is only if those results are in line with what other people get or if there is something terribly wrong here.

Media Info for UHD encode:

Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format_Commercial_IfAny : HDR10
Format-Profil : Main 10@L5.1@High
Codec-ID : V_MPEGH/ISO/HEVC
Dauer : 2 h 20 min
Bitrate : 4 411 kb/s
Breite : 3 840 Pixel
Höhe : 2 160 Pixel
Bildseitenverhältnis : 16:9
Modus der Bildwiederholungsrate : konstant
Bildwiederholungsrate : 23,976 (24000/1001) FPS
ColorSpace : YUV
ChromaSubsampling/String : 4:2:0
BitDepth/String : 10 bits
Bits/(Pixel*Frame) : 0.022
Stream-Größe : 4,32 GiB (47%)
verwendete Encoder-Bibliothek : x265 2.9+2-7e978ed93d60:[Windows][GCC 8.2.0][64 bit] 10bit
Kodierungseinstellungen :
cpuid=1111039 / frame-threads=2 / numa-pools=32,0 / wpp / no-pmode / pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=3840x2160 / interlace=0 / total-frames=201740 / level-idc=51 / high-tier=1 / uhd-bd=0 / ref=3 / no-allow-non-conformance / repeat-headers / annexb / no-aud / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=24 / keyint=240 / gop-lookahead=0 / bframes=4 / b-adapt=2 / b-pyramid / bframe-bias=0 / rc-lookahead=20 / lookahead-slices=8 / scenecut=40 / radl=0 / no-intra-refresh / ctu=64 / min-cu-size=8 / no-rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=0 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / no-strong-intra-smoothing / max-merge=2 / limit-refs=3 / no-limit-modes / me=1 / subme=2 / merange=57 / temporal-mvp / weightp / no-weightb / no-analyze-src-pics / deblock=-1:-1 / no-sao / no-sao-non-deblock / rd=3 / no-early-skip / rskip / no-fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=0.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=18.0 / qcomp=0.60 / qpstep=4 / stats-write=0 / stats-read=0 / vbv-maxrate=99000 / vbv-bufsize=99000 / vbv-init=0.9 / crf-max=0.0 / crf-min=0.0 / ipratio=1.40 / pbratio=1.30 / aq-mode=3 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=1 / overscan=0 / videoformat=5 / range=0 / colorprim=9 / transfer=16 / colormatrix=9 / chromaloc=0 / display-window=0 / master-display=G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(10000000,50) / max-cll=0,0 / min-luma=0 / max-luma=1023 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / no-opt-cu-delta-qp / no-aq-motion / hdr / hdr-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=5 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-mv-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei
Default : Ja
Forced : Nein
colour_range : Limited
colour_primaries : BT.2020
transfer_characteristics : PQ
matrix_coefficients : BT.2020 non-constant
MasteringDisplay_ColorPrimaries : Display P3
MasteringDisplay_Luminance : min: 0.0050 cd/m2, max: 1000 cd/m2




Media Info fpr a 1080p encode:


Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format-Profil : Main 10@L4@Main
Codec-ID : V_MPEGH/ISO/HEVC
Dauer : 2 h 22 min
Bitrate : 10,2 Mb/s
Breite : 1 920 Pixel
Höhe : 800 Pixel
Bildseitenverhältnis : 2,40:1
Modus der Bildwiederholungsrate : konstant
Bildwiederholungsrate : 23,976 (24000/1001) FPS
ColorSpace : YUV
ChromaSubsampling/String : 4:2:0
BitDepth/String : 10 bits
Bits/(Pixel*Frame) : 0.276
Stream-Größe : 10,1 GiB (72%)
verwendete Encoder-Bibliothek : x265 2.8:[Windows][GCC 7.1.0][64 bit] 10bit
Kodierungseinstellungen :
cpuid=1111039 / frame-threads=2 / numa-pools=32,0 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=1920x800 / interlace=0 / total-frames=0 / level-idc=0 / high-tier=1 / uhd-bd=0 / ref=4 / no-allow-non-conformance / no-repeat-headers / annexb / no-aud / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=24 / keyint=240 / gop-lookahead=0 / bframes=4 / b-adapt=2 / b-pyramid / bframe-bias=0 / rc-lookahead=20 / lookahead-slices=5 / scenecut=40 / radl=0 / no-intra-refresh / ctu=32 / min-cu-size=8 / no-rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=0 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / no-strong-intra-smoothing / max-merge=2 / limit-refs=3 / no-limit-modes / me=3 / subme=4 / merange=27 / temporal-mvp / weightp / no-weightb / no-analyze-src-pics / deblock=-1:-1 / no-sao / no-sao-non-deblock / rd=4 / no-early-skip / rskip / no-fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=3.00 / psy-rdoq=0.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=18.0 / qcomp=0.63 / qpstep=4 / stats-write=0 / stats-read=0 / ipratio=1.40 / pbratio=1.30 / aq-mode=3 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=1 / overscan=0 / videoformat=5 / range=0 / colorprim=1 / transfer=1 / colormatrix=1 / chromaloc=0 / display-window=0 / max-cll=0,0 / min-luma=0 / max-luma=1023 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / no-opt-cu-delta-qp / no-aq-motion / no-hdr / no-hdr-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=5 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-mv-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei
Default : Ja
Forced : Nein
colour_range : Limited
colour_primaries : BT.709
transfer_characteristics : BT.709
matrix_coefficients : BT.709

Cary Knoop
4th November 2018, 17:39
Did you properly convert the Rec2020/PQ to Rec709 before re-encoding to H.265?

Boulder
7th November 2018, 13:19
As I wrote in the x265 encoder thread, CRF needs to be quite a bit lower for HDR encodes to have the same quality level as SDR ones. CRF 18 is not really low, I've used 14-15 based on my tests.