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• FFMPEG Audio/video out of sync after cutting and concatonating even after transcoding

  4 mai 2020, par Ham789

  I am attempting to take cuts from a set of videos and concatonate them together with the concat demuxer.

  



  However, the audio is out of sync of the video in the output. The audio seems to drift further out of sync as the video progresses. Interestingly, if I click to seek another time in the video with the progress bar on the player, the audio becomes synced up with the video but then gradually drifts out of sync again. Seeking to a new time in the player seems to reset the audio/video. It is like they are being played back at different rates or something. I get this behaviour in both Quicktime and VLC players.

  



  For each video, I decode it, trim a clip from it and then encode it to 4k resolution at 25 fps with its audio :

  



  ffmpeg -ss 0.5 -t 0.5 -i input_video1.mp4 -r 25 -vf scale=3840:2160 output_video1.mp4

  



  I then take each of these videos and concatonate them together with the concat demuxer :

  



  ffmpeg -f concat -safe 0 -i cut_videos.txt -c copy -y output.mp4

  



  I am taking short cuts of each video (approximately 0.5s)

  



  I am using Python's subprocess to automate the cutting and concatonating of the videos.

  



  I am not sure if this happens because of the trimming or concatenation steps but when I play back the intermediate cut video files (output_video1.mp4 in the above command), there seems to be some silence before the audio comes in at the start of the video.

  



  When I concatonate the videos, I sometimes get a lot of these warnings however the audio still becomes out of sync even when I do not get them :

  



  [mp4 @ 0000021a252ce080] Non-monotonous DTS in output stream 0:1; previous: 51792, current: 50009; changing to 51793. This may result in incorrect timestamps in the output file.

  



  From this post, it seems to be a problem with cutting the videos and their timestamps. The solution proposed in the post is to decode, cut and then encode the video however I am already doing that.

  



  How can I ensure the audio and video are in sync ? Am I transcoding incorrectly ? This seems to be the only solution I can find online however it does not seem to work.

  



  UPDATE :

  



  I took inspiration from this post and seperated the audio and video from output_video1.mp4 using :

  



  ffmpeg -i output_video1.mp4 -acodec copy -vn video.mp4

  



  and

  



  ffmpeg -i output_video1.mp4 -vcodec copy -an audio.mp4

  



  I then compared the durations of video.mp4 and audio.mp4 and got 0.57s and 0.52s respectively. Since the video is longer, this explains why there is a period of silence in the videos. The post then suggests transcoding is the solution however as you can see from the code above that does not work for me.

  



  Sample Output Log for the Trim Command

  



    built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input_video1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:00:04.06, start: 0.000000, bitrate: 14266 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 3840x2160, 14268 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : Core Media Video
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 94 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
File 'output_video1.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7fcae4001e00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7fcae4001e00] profile High, level 5.1
[libx264 @ 0x7fcae4001e00] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output_video1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 3840x2160, q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
    Metadata:
      handler_name    : Core Media Video
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 69 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
      encoder         : Lavc58.54.100 aac
frame=   14 fps=7.0 q=-1.0 Lsize=     928kB time=00:00:00.51 bitrate=14884.2kbits/s dup=0 drop=1 speed=0.255x    
video:922kB audio:5kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.194501%
[libx264 @ 0x7fcae4001e00] frame I:1     Avg QP:21.06  size:228519
[libx264 @ 0x7fcae4001e00] frame P:4     Avg QP:22.03  size: 85228
[libx264 @ 0x7fcae4001e00] frame B:9     Avg QP:22.88  size: 41537
[libx264 @ 0x7fcae4001e00] consecutive B-frames: 14.3%  0.0%  0.0% 85.7%
[libx264 @ 0x7fcae4001e00] mb I  I16..4: 27.6% 64.3%  8.1%
[libx264 @ 0x7fcae4001e00] mb P  I16..4:  9.1% 10.7%  0.2%  P16..4: 48.5%  7.3%  3.9%  0.0%  0.0%    skip:20.2%
[libx264 @ 0x7fcae4001e00] mb B  I16..4:  1.1%  1.0%  0.0%  B16..8: 44.5%  2.9%  0.2%  direct: 8.3%  skip:42.0%  L0:45.6% L1:53.2% BI: 1.2%
[libx264 @ 0x7fcae4001e00] 8x8 transform intra:58.2% inter:93.4%
[libx264 @ 0x7fcae4001e00] coded y,uvDC,uvAC intra: 31.4% 62.2% 5.2% inter: 11.4% 30.9% 0.0%
[libx264 @ 0x7fcae4001e00] i16 v,h,dc,p: 15% 52% 12% 21%
[libx264 @ 0x7fcae4001e00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 33% 32%  2%  2%  2%  4%  2%  4%
[libx264 @ 0x7fcae4001e00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20% 39%  9%  3%  4%  4% 12%  3%  4%
[libx264 @ 0x7fcae4001e00] i8c dc,h,v,p: 43% 36% 18%  3%
[libx264 @ 0x7fcae4001e00] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7fcae4001e00] ref P L0: 69.3%  8.0% 14.8%  7.9%
[libx264 @ 0x7fcae4001e00] ref B L0: 88.1%  9.2%  2.6%
[libx264 @ 0x7fcae4001e00] ref B L1: 90.2%  9.8%
[libx264 @ 0x7fcae4001e00] kb/s:13475.29
[aac @ 0x7fcae4012400] Qavg: 125.000```


  


• Combine multiple video and single audio stream into a single output

  15 janvier 2020, par Prashant Saraswat

  I am trying to record an online meeting.
  During the meeting I will receive continuous audio and intermittent video

  • A. Audio B. Video1 C. Video 2

  The Audio stream will span the length of the call. The video1 and video2 streams will be somewhere in the middle.

  Assuming I know the timestamps for all of these streams, how do I combine them in one video ?

  Consider the scenario where the audio stream starts at Tbegin and ends at Tend. The video1 stream starts at T1 and ends at T2. The video2 stream starts at T3 and ends at T4.

  We can assume that the audio stream is of type mp3 and the other streams are of type mp4

• Removing / Overlaying logo on mp4 video format with ffmpeg on linux

  13 juillet 2016, par SilverShadow

  I’m trying to remove logo from an .mp4 video format with ffmpeg on linux machine without re-encoding (for preserving the same quality) with the following command :

  ffmpeg -i input.mp4 -vf delogo=x=270:y=190:w=40:h=40 -c:a copy output.mp4

  and it give me the following errors :

  Unrecognized option 'vf'

  then a new error came up :

  Unable to find a suitable output format for 'delogo=x=270:y=190:w=40:h=40'

  ffmpeg always updating and it seems that they change command line arguments alot so any material or tutorial i find online seems to get out-dated quickly

  I review their website documentation but can’t get it to work, I think i’m missing something...?

  so what is the correct command line in linux shell also, how to view or find out exactly the area coordinates to be removed before actually removing logo/overlaying it and keep testing every while

  and how to overlay a solid color in certain area instead of removing logo transparently as well ?