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• How to extract time-accurate video segments with ffmpeg ?

  25 mai 2016, par Jim Miller

  This is not a particularly new question area around here, but I’ve tried what’s been suggested there without much luck. So, my story :

  I’ve got a hunk of 15 seconds of straight-from-the-camera.mov video out of which I want to extract a specific chunk, which I can identify by start time and stop time, in seconds. I started by trying to do what I’ll call a "copy extraction" : to get seconds 9 to 12,

  ffmpeg -i test.mov -vcodec copy -acodec copy -ss 9 -to 12 test-copy.mov

  This was a not-bad start, but there are some black frames at the beginning and end of the clip, which I can’t have — it has to be a clean edit from the original. So, I tried recoding the original into a new, trimmed clip :

  ffmpeg -i test.mov -ss 00:00:09 -t 00:00:03 test-out.mov

  This is better, but not quite : There are no longer any black frames at the beginning of the clip, but they’re still there at the end.

  After some more browsing and reading, I then suspected that the problem is that ffmpeg is having trouble finding the proper points because of a lack of keyframes in the original video. So I recoded the original video to (presumably) add keyframes, in a couple of different ways. Since I want to be able to pick video at boundaries of a second ("from 9 seconds to 12 seconds"), I tried, copying various suggestions around the web,

  ffmpeg -i test.mov -force_key_frames "expr:gte(t, n_forced)" test-forced.mp4

  and

  ffmpeg -i test.mov -g 1 test-g-inserted.mp4

  (I built these as mp4’s based on some comments about an mp4 container being needed to support the keyframe search, but I’m honestly just hacking here.) I then tried the extraction as before, but on these new videos that presumably now have keyframes in them. No luck — both seem to be about the same ; the start is OK but there are still black frames at the end. (FWIW, both test-forced.mp4 and test-g-inserted.mp4 also have trailing black frames.)

  So : I’m still stuck, and would like to not be. Any insights out there as to what I’m doing wrong ? I feel like I’m close, but I really need to get rid of those trailing black frames....

• FFmpeg encoding slow for 4K HDR content

  1er mars 2023, par Geno Diaz

  When processing 4K input with the following configuration it is taking upwards of 2 minutes to process a 35s, 60fps, 4K HDR clip recorded from an iPhone. Is this the expected performance or is there an inefficiency within the configuration that is causing this ?

  


  In comparison, running this configuration on a 35s, 30fps, 4K non-HDR clip, only takes about 20 seconds.

  


  ffmpeg 
-i "input path" 
-y 
-filter:v scale=w=2160:h=3840 
-threads 4 
-r 59.94 
-c:v libx264 
-preset veryfast 
-vsync 1 
-tune film 
-maxrate 6000k 
-bufsize 5400k 
-g 60 
-x264opts no-scenecut 
-c:a aac 
-af aresample=async=1:min_hard_comp=0.100000:first_pts=0 
-ac 2 
-b:a 128k 
-ar 44100 
-vf zscale=transfer=linear:npl=100,
  format=gbrpf32le,
  zscale=primaries=bt709,
  tonemap=tonemap=hable:desat=0,
  zscale=transfer=bt709:matrix=bt709:range=tv,
  format=yuv420p 
-sws_flags full_chroma_int+full_chroma_inp 
-pix_fmt yuv420p 
"outputfile".mp4


  


• cpu.c:253 : x264_cpu_detect : Assertion

  12 octobre 2017, par user6341251

  environment :
  ubuntu 16.04_x64 server
  install ffmpeg through apt-get install
  python 3
  

  when I try

  from moviepy.editor import *
clip = VideoFileClip("/root/video.mp4")
clip.ipython_display(width=280)

  Traceback (most recent call last) :
  File "", line 1, in
  File "/usr/local/lib/python2.7/dist-packages/moviepy/video/io/html_tools.py", line 219, in ipython_display
  center=center, rd_kwargs=rd_kwargs, **html_kwargs))
  File "/usr/local/lib/python2.7/dist-packages/moviepy/video/io/html_tools.py", line 97, in html_embed
  clip.write_videofile(**kwargs)
  File "", line 2, in write_videofile
  File "/usr/local/lib/python2.7/dist-packages/moviepy/decorators.py", line 54, in requires_duration
  return f(clip, *a, **k)
  File "", line 2, in write_videofile
  File "/usr/local/lib/python2.7/dist-packages/moviepy/decorators.py", line 137, in use_clip_fps_by_default
  return f(clip, *new_a, **new_kw)
  File "", line 2, in write_videofile
  File "/usr/local/lib/python2.7/dist-packages/moviepy/decorators.py", line 22, in convert_masks_to_RGB
  return f(clip, *a, **k)
  File "/usr/local/lib/python2.7/dist-packages/moviepy/video/VideoClip.py", line 349, in write_videofile
  progress_bar=progress_bar)
  File "/usr/local/lib/python2.7/dist-packages/moviepy/video/io/ffmpeg_writer.py", line 216, in ffmpeg_write_video
  writer.write_frame(frame)
  File "/usr/local/lib/python2.7/dist-packages/moviepy/video/io/ffmpeg_writer.py", line 178, in write_frame
  raise IOError(error)
  IOError : [Errno 32] Broken pipe

  MoviePy error : FFMPEG encountered the following error while writing file temp.mp4 :

  ffmpeg : common/cpu.c:253 : x264_cpu_detect : Assertion ` !(cpu&(0x0000040|0x0000080))’ failed.

  what happend ?

  ---

  @Ronald S. Bultje
  

  I am using a virtual machine

  processor : 0
  vendor_id : GenuineIntel
  cpu family : 6
  model : 13
  model name : QEMU Virtual CPU version (cpu64-rhel6)
  stepping : 3
  microcode : 0x1
  cpu MHz : 3504.000
  cache size : 4096 KB
  physical id : 0
  siblings : 1
  core id : 0
  cpu cores : 1
  apicid : 0
  initial apicid : 0
  fpu : yes
  fpu_exception : yes
  cpuid level : 13
  wp : yes
  flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm rep_good nopl eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 smep bmi2 xsaveopt
  bugs :
  bogomips : 7008.00
  clflush size : 64
  cache_alignment : 64
  address sizes : 39 bits physical, 48 bits virtual
  power management :