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• A pragmatic strategy to merge multiple video files

  19 juin 2021, par saurav

  I currently am working on recording a multiparty video conference which supports up to 6 participants. I am recording the conference using a media server and storing audio/video streams individually for every participant.

  


  Next, I need to merge those individual recordings into a single video file and upload it to a cloud storage like aws s3. For this I am considering 2 options, either Gstreamer or FFMPEG. I am leaning towards FFMPEG as I have used FFMPEG previously. I currently am playing with FFMPEG things like the hstack and vstack filters etc.

  


  Here is the FFMPEG command I recently used to join 2 webm videos of 2 mins 40sec and 1min 40sec to create a mp4 video file for upload. Both the videos are 1280x720 in this case but I have included the scale part because in real life scenario different participants joining with different cameras produces video files of different resolution which is a problem for the hstack/vstack filter. Therefore, to make the video resolutions of all participant consistent, I have included the scale property.

  


  ffmpeg -i 1.webm -i 2.webm -filter_complex "[0:v]scale=1280:720,setsar=1[l];[1:v]scale=1280:720,setsar=1[r];[l][r]hstack;[0][1]amix" output-1280x720.mp4


  


  Currently I am facing 2 issues with this command.

  


  


  1. The output mp4 file is very big, in this case 140Mb (approx) for a less than 3 minutes video.

     


  


  2. How do I add delay to any video before starting to merge ?
     
Currently the videos are going out of sync if all the participants don't join at the same time which is highly unlikely to happen in a real world scenario.

     


  


  


  Any pointer in the right direction will be highly appreciated.

  


  Here is a log sample from FFmpeg (or see the full log link) :

  


  ffmpeg version 4.2.4-1ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  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, matroska,webm, from '3.webm':
  Metadata:
    title           : FFmpeg
    ENCODER         : Lavf58.29.100
  Duration: 00:01:39.63, start: 0.000000, bitrate: 707 kb/s
    Stream #0:0: Video: vp8, yuv420p(tv, bt470bg/unknown/unknown, progressive), 1280x720, SAR 1:1 DAR 16:9, 1k tbr, 1k tbn, 1k tbc (default)
    Metadata:
      DURATION        : 00:01:39.618000000
    Stream #0:1: Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 00:01:39.629000000
Input #1, matroska,webm, from '4.webm':
  Metadata:
    title           : FFmpeg
    ENCODER         : Lavf58.29.100
  Duration: 00:02:39.07, start: 0.000000, bitrate: 708 kb/s
    Stream #1:0: Video: vp8, yuv420p(tv, bt470bg/unknown/unknown, progressive), 1280x720, SAR 1:1 DAR 16:9, 1k tbr, 1k tbn, 1k tbc (default)
    Metadata:
      DURATION        : 00:02:39.050000000
    Stream #1:1: Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 00:02:39.068000000
Stream mapping:
  Stream #0:0 (vp8) -> scale
  Stream #0:1 (opus) -> amix:input0
  Stream #1:0 (vp8) -> scale
  Stream #1:1 (opus) -> amix:input1
  hstack -> Stream #0:0 (libx264)
  amix -> Stream #0:1 (aac)
Press [q] to stop, [?] for help
[libx264 @ 0x562b4842a500] using SAR=1/1
[libx264 @ 0x562b4842a500] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x562b4842a500] profile High, level 6.1
[libx264 @ 0x562b4842a500] 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=18 lookahead_threads=3 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-new.mp4':
  Metadata:
    title           : FFmpeg
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p(progressive), 2560x720 [SAR 1:1 DAR 32:9], q=-1--1, 1k fps, 16k tbn, 1k tbc (default)
    Metadata:
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      encoder         : Lavc58.54.100 aac

frame=  129 fps=0.0 q=33.0 size=       0kB time=00:00:00.23 bitrate=   1.6kbits/s dup=123 drop=0 speed=0.44x    
frame=  257 fps=228 q=33.0 size=       0kB time=00:00:00.51 bitrate=   0.8kbits/s dup=243 drop=0 speed=0.455x    
frame=  379 fps=224 q=33.0 size=     256kB time=00:00:00.73 bitrate=2855.1kbits/s dup=358 drop=0 speed=0.434x    
frame=  497 fps=222 q=33.0 size=     256kB time=00:00:00.86 bitrate=2431.5kbits/s dup=469 drop=0 speed=0.386x    
 
...
More than 1000 frames duplicated
...
  
frame=158751 fps=196 q=33.0 size=  134656kB time=00:02:39.00 bitrate=6937.4kbits/s dup=151385 drop=0 speed=0.196x    
frame=158851 fps=196 q=33.0 size=  134912kB time=00:02:39.00 bitrate=6950.6kbits/s dup=151482 drop=0 speed=0.196x    
frame=158983 fps=196 q=33.0 size=  134912kB time=00:02:39.00 bitrate=6950.6kbits/s dup=151610 drop=0 speed=0.196x    
frame=159081 fps=196 q=-1.0 Lsize=  137197kB time=00:02:39.07 bitrate=7065.2kbits/s dup=151706 drop=0 speed=0.196x    

video:132693kB audio:2494kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.486001%

[libx264 @ 0x562b4842a500] frame I:637   Avg QP:17.73  size:123895
[libx264 @ 0x562b4842a500] frame P:40088 Avg QP:19.73  size:  1134
[libx264 @ 0x562b4842a500] frame B:118356 Avg QP:27.54  size:    97
[libx264 @ 0x562b4842a500] consecutive B-frames:  0.8%  0.0%  0.0% 99.2%
[libx264 @ 0x562b4842a500] mb I  I16..4: 11.1% 67.3% 21.6%
[libx264 @ 0x562b4842a500] mb P  I16..4:  0.1%  0.1%  0.0%  P16..4:  2.6%  0.4%  0.3%  0.0%  0.0%    skip:96.5%
[libx264 @ 0x562b4842a500] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.7%  0.0%  0.0%  direct: 0.0%  skip:99.3%  L0:38.7% L1:61.3% BI: 0.0%
[libx264 @ 0x562b4842a500] 8x8 transform intra:66.8% inter:71.4%
[libx264 @ 0x562b4842a500] coded y,uvDC,uvAC intra: 81.8% 89.5% 72.3% inter: 0.2% 0.4% 0.0%
[libx264 @ 0x562b4842a500] i16 v,h,dc,p: 25% 21% 17% 37%
[libx264 @ 0x562b4842a500] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33% 22% 12%  4%  5%  6%  6%  6%  6%
[libx264 @ 0x562b4842a500] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 42% 24%  6%  4%  5%  5%  6%  4%  4%
[libx264 @ 0x562b4842a500] i8c dc,h,v,p: 42% 24% 26%  9%
[libx264 @ 0x562b4842a500] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x562b4842a500] ref P L0: 82.4% 11.5%  5.3%  0.8%
[libx264 @ 0x562b4842a500] ref B L0: 83.0% 16.9%  0.1%
[libx264 @ 0x562b4842a500] ref B L1: 94.9%  5.1%
[libx264 @ 0x562b4842a500] kb/s:6833.11
[aac @ 0x562b4842b540] Qavg: 239.393


  


• ffmpeg codec error on audio file

  31 juillet 2013, par foosion

  I have some m4a files that will not play properly using the google music player app on my Android phone, although they play fine on most everything else. I thought the problem was the container and thought "ffmpeg -i bad.m4a -codec copy good.m4a" might help. However, when I run on the problem files, I get error messages. Running this command on non-problem files has not generated error messages.

  Please suggest ways to fix (other than re-encoding).

      [D:\temp\dl]ffmpeg -i "01 - The Day Begins.m4a" -codec copy day.m4a
  
  ffmpeg version N-55066-gc96b3ae Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Jul 29 2013 18:05:45 with gcc 4.7.3 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
  
  isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
  
  le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
  
  e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
  
  ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
  
  ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
  
  eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-
  
  amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --
  
  enable-libxvid --enable-zlib
  
    libavutil      52. 40.100 / 52. 40.100
  
    libavcodec     55. 19.100 / 55. 19.100
  
    libavformat    55. 12.102 / 55. 12.102
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 82.100 /  3. 82.100
  
    libswscale      2.  4.100 /  2.  4.100
  
    libswresample   0. 17.103 /  0. 17.103
  
    libpostproc    52.  3.100 / 52.  3.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 00000000002da300] stream 0, timescale not set
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '01 - The Day Begins.m4a':
  
    Metadata:
  
      major_brand     : m4a
  
      minor_version   : 0
  
      compatible_brands: M4A mp4isom
  
      creation_time   : 2003-07-06 20:27:46
  
      track           : 1
  
      genre           : Rock
  
      title           : The Day Begins
  
      artist          : Moody Blues
  
      album           : Days of Future Passed
  
      date            : 1967
  
    Duration: 00:05:50.83, start: 0.000000, bitrate: 166 kb/s
  
      Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 15
  
  9 kb/s
  
      Metadata:
  
        creation_time   : 2003-07-06 20:27:46
  
        handler_name    : Apple Sound Media Handler
  
      Stream #0:1(eng): Data: none (mp4s / 0x7334706D)
  
      Metadata:
  
        creation_time   : 2003-07-06 20:27:46
  
        handler_name    : Apple MPEG-4 Scene Media Handler
  
      Stream #0:2(eng): Data: none (mp4s / 0x7334706D)
  
      Metadata:
  
        creation_time   : 2003-07-06 20:27:46
  
        handler_name    : Apple MPEG-4 ODSM Media Handler
  
      Stream #0:3: Video: png, rgb24, 240x240 [SAR 2834:2834 DAR 1:1], 90k tbr, 90
  
  k tbn, 90k tbc
  
  [ipod @ 000000000031dd40] track 0: could not find tag, codec not currently suppo
  
  rted in container
  
  Output #0, ipod, to 'day.m4a':
  
    Metadata:
  
      major_brand     : m4a
  
      minor_version   : 0
  
      compatible_brands: M4A mp4isom
  
      date            : 1967
  
      track           : 1
  
      genre           : Rock
  
      title           : The Day Begins
  
      artist          : Moody Blues
  
      album           : Days of Future Passed
  
      encoder         : Lavf55.12.102
  
      Stream #0:0: Video: png, rgb24, 240x240 [SAR 2834:2834 DAR 1:1], q=2-31, 90k
  
   tbn, 90k tbc
  
      Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, 159 kb/s
  
  
  
      Metadata:
  
        creation_time   : 2003-07-06 20:27:46
  
        handler_name    : Apple Sound Media Handler
  
  Stream mapping:
  
    Stream #0:3 -> #0:0 (copy)
  
    Stream #0:0 -> #0:1 (copy)
  
  Could not write header for output file #0 (incorrect codec parameters ?): Error
  
  number -1 occurred

• Official RealVideo Specifications

  29 juillet 2010, par Multimedia Mike — General

  A little birdie tipped me off to a publicly-accessible URL on the Helix community site (does anyone actually use Helix ?) that contains a bunch of specifications for RealVideo 8 and 9. I have been sifting through the documents to see exactly what they contain as the different files seem to be higher revisions of the same documents. Here is the title, date, and version of each PDF document :

  • RNDecoderPerformanceARM.pdf : Decoder Performance on StrongARM and XScale ; May 12, 2003 ; Version 1.1
  • rv89_decoder_summary.pdf : RealVideo 8/9 Combo Decoder Summary ; October 23, 2002 ; Version 1.0
  • rv9_dec_external_spec_v14.pdf : RealVideo 9 External Specification ; November 7, 2003 ; Version 1.4
  • rv8_dec_external_spec_v20.pdf : RealVideo 8 External Specification ; September 19, 2002 ; Version 2.0
  • RV8DecoderExternalSpecificationv201.pdf : RealVideo 8 External Specification ; October 20, 2006 ; Version 2.01
  • RV8DecoderExternalSpecificationv202.pdf : RealVideo 8 External Specification ; April 23, 2007 ; Version 2.02
  • RV8DecoderExternalSpecificationv203.pdf : RealVideo 8 External Specification ; July 20, 2007 ; Version 2.03
  • RV8DecoderExternalSpecificationv21.pdf : RealVideo 8 External Specification ; September 11, 2007 ; Version 2.1
  • RV9DecoderExternalSpecificationv15.pdf ; RealVideo 9 External Specification ; January 26, 2002 ; Version 1.5
  • RV9DecoderExternalSpecificationv16.pdf ; RealVideo 9 External Specification ; August 17, 2005 ; Version 1.6
  • RV9DecoderExternalSpecificationv18.pdf ; RealVideo 9 External Specification ; September 11, 2007 ; Version 1.8

  Additionally, there is an Excel spreadsheet entitled realvideo-faq.xls that appears to contain some general tech support advice for using Real’s official code. There are also 3 ZIP archives which contain profiling information about the official source code (post processing and entropy decoding top the charts which is no big surprise).

  I guess the latest version of each document (the ones dated September 11, 2007) are worth mirroring. Unfortunately, those latest document versions use a terrible font.