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x264 encoding taking longer when encoding static frames (than
14 septembre 2015, par DaniloHi, I'm using x264 for live video streaming and I've noticed that the thread responsible for encoding uses more cpu (sometimes 50% more with 1920x1080) when the video stream is frozen (i.e.: camera is sending the same frame over an over again) or when I make it encode the same image over and over again.
This seems somewhat counter intuitive to me, as I would expect x264 to use more processing power when encoding complex scenes other then static ones.
My encoder settings are the following:
1280x720 fps=25/1 timebase=0/0 bitdepth=8 cabac=0 ref=1 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=2 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=1 lookahead_threads=0 sliced_threads=0 slice_max_size=1190 nr=60 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=1200 keyint_min=120 scenecut=40 intra_refresh=0 rc_lookahead=0 rc=crf mbtree=0 crf=24.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=1024 vbv_bufsize=350 crf_max=35.0 nal_hrd=noneI created a github gist based on the example.c encoder bundled in x264's source code and tested encoding times with it. (You can find it here: https://gist.github.com/danilogr/ab4976ff4e0831ab274b)
Average encoding time for the static scene is ~38% bigger than for a scene with movements. (You can find my test case and also the output from my test encoder on the link above).
I've also noticed that by setting
scenecut=0, subme=0, trellis=0 and me=diaI can get rid of this problem, but with noticeable quality decrease. Could anyone, please, shed some light on the reasons for this odd behavior? Also, what can be done in order to avoid this situation without a major decrease in quality?
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In FFmpeg, encoding anything lower than slow preset takes video to level 5
1er septembre 2015, par Leo ZerinoWhy whenever I use any preset lower or equal to slow, it makes my video High@L5 (profile high / level 5)? It doesn't make sense to me, I always tought that levels were associeted with frame size, frame rate and data rate only
I've searched all over for a relation between presets and levels in x264 encoding through FFmpeg, but couldn't find any.
My only concern is compatibility, since anything above 4 tends to be exotic to most players.
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Encoding H.264 CBR videos with FFmpeg
27 août 2015, par CornstalksI'm trying to encode a video with ffmpeg into H.264 (via the libx264 library) with a constant bit rate. I know, I know, VBR is often preferred, but for this specific job I'm required to use CBR (just as long as it's so many kilobytes per second; it doesn't have to be an exact kilobytes per frame, afaik). My sample video I'm using to test is from here: http://a1408.g.akamai.net/5/1408/1388/2005110403/1a1a1ad948be278cff2d96046ad90768d848b41947aa1986/sample_iTunes.mov.zip (it comes from http://support.apple.com/kb/HT1425)
I can get a constant bit rate when encoding the video with MPEG-4 Video (using the commands
ffmpeg -i sample_iTunes.mov -b 819968 -minrate 819968 -maxrate 819968 out.mov), and the bit rate is as expected. Reading the video's specs via the QuickTime Inspector, it's got a data rate of 844.94 kbit/s. Cool.However, when I change the codec to libx264, it seems to completely ignore my bitrate requests! The command I'm trying is "
ffmpeg -i sample_iTunes.mov -vcodec libx264 -vpre medium -b 819968 -vb 819968 -minrate 819968 -maxrate 819968 -bufsize 400000 test.mov". But when I check the video's specs via the QuickTime Inspector, it's got a data rate of 254.74 kbit/s. WTF? That's not even close!I've tried changing so many parameters and adding tons of different things, and I've spent 2 days googling this, but I can't seem to get it to work. If I encode the video with the MainConcept H.264 encoder, I can get a constant bitrate, but I need this to work with ffmpeg.
If someone can help me figure out how to do CBR H.264 encoding with FFmpeg, I will love you forever!
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x264 library speed - Altivec vs SSE4 -
15 août 2015, par Asain KujovicI have simple cheap dualcore intel-3ghz-debian and access to super-expensive powerPc7-Aix.
And after few days of strugle, i compiled libx264 and tested it on both computers:
- GCC: library x264 on intel (with SSE2 capabilities) and
- GCC on 16 core powerPc (with altivec).
... and result is that cheap intel is x2 times faster ! (with altivec disabled, intel is 10x times faster)
My question: is this normal? Does all other powerPC-users have same results? Can powerPc-altivec-optimisation of x264 library work at same speed with intel... or MMX/SSE optimisation is officially at least 2 times faster for this library?
I am not interested in multi-thread options. Number of cores and threads are irrelevant. Just simple one-thread x264 encoding with default "medium preset" using rawvideo as source, sse vs altivec.
Maybe native Aix XLC compiler provide better results? (i managed only gcc to work)
... mac-powerpc-users maybe know something about this.
powrPc7-Aix:$ time (cat raw10sec.y4m |x264 --input-res 720x576 --fps 50 -o /dev/null -) x264: 64-bit XCOFF x264 [info]: using cpu capabilities: Altivec time: real 0m33.559s --- intelDebian:$ time (cat raw10sec.y4m |x264 --input-res 720x576 --fps 50 -o /dev/null -) x264: ELF 32-bit LSB executable x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64 time: real 0m16.503s -
understanding libx264 output [closed]
11 août 2015, par nmxprimeI used libx264 in ffmpeg to encode . Finally i got below output .
Can anyone guide me understanding & interpreting this?? Any reference/documentation?
01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] frame I:7 Avg QP:27.51 size: 11996 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] frame P:32 Avg QP:26.90 size: 217 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] frame B:25 Avg QP:32.73 size: 39 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] consecutive B-frames: 20.0% 80.0% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] mb I I16..4: 74.1% 17.0% 8.9% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] mb P I16..4: 0.7% 0.1% 0.0% P16..4: 2.0% 0.3% 0.2% 0.0% 0.0% skip:96.6% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 1.2% 0.0% 0.0% direct: 0.1% skip:98.8% L0: 5.5% L1:94.5% BI: 0.0% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] final ratefactor: 22.43 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] 8x8 transform intra:16.9% inter:51.1% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] coded y,uvDC,uvAC intra: 12.8% 27.2% 24.4% inter: 0.3% 0.6% 0.0% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] i16 v,h,dc,p: 95% 5% 0% 0% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 2% 30% 60% 0% 1% 0% 2% 0% 4% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 7% 58% 10% 2% 4% 2% 9% 1% 8% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] i8c dc,h,v,p: 14% 81% 3% 3% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] Weighted P-Frames: Y:0.0% UV:0.0% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] ref P L0: 81.2% 16.6% 1.8% 0.4% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] ref B L0: 70.8% 29.2% 01-01 06:34:43.650: I/stderr(6603): [libx264 @ 0xdd2040] kb/s:287.21Edit: I want to know what determines rate factor? Is it relevant to fps? What is QP and it's relation with rate factor?
Thank You!!
