title: FFMPEG results in a silent video when trying to combine video and audio tracks
body: <p>I'm using the following command to combine a video and an audio track.</p>
  
  <pre><code>ffmpeg -y -i /var/www/temp/merged.mp4 -i /var/www/temp/combined.mp3 -strict -2 /var/www/temp/videoExtouiulbjryzxlehjj2.mp4
  </code></pre>
  
  <p>Edit:</p>
  
  <p>Here is the output from the first command</p>
  
  <pre><code>ffmpeg version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2000-2016 the FFmpeg developers
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
    libavutil      54. 15.100 / 54. 15.100
    libavcodec     56. 13.100 / 56. 13.100
    libavformat    56. 15.102 / 56. 15.102
    libavdevice    56.  3.100 / 56.  3.100
    libavfilter     5.  2.103 /  5.  2.103
    libavresample   2.  1.  0 /  2.  1.  0
    libswscale      3.  1.101 /  3.  1.101
    libswresample   1.  1.100 /  1.  1.100
    libpostproc    53.  3.100 / 53.  3.100
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/temp/merged.mp4':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      encoder         : Lavf56.15.102
    Duration: 00:02:31.80, start: 0.000000, bitrate: 2384 kb/s
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 2381 kb/s, 25.43 fps, 29.97 tbr, 11988 tbn, 59.94 tbc (default)
      Metadata:
        handler_name    : VideoHandler
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 0 kb/s (default)
      Metadata:
        handler_name    : SoundHandler
  Input #1, mp3, from '/var/www/temp/audioTrack.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.94, start: 0.011995, bitrate: 128 kb/s
      Stream #1:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
      Metadata:
        encoder         : Lavf
  [libx264 @ 0x1e903a0] using SAR=1/1
  [libx264 @ 0x1e903a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX AVX2 FMA3 LZCNT BMI2
  [libx264 @ 0x1e903a0] profile High, level 4.0
  [libx264 @ 0x1e903a0] 264 - core 142 r2495 6a301b6 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - 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=6 lookahead_threads=1 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 '/var/www/temp/videoExtvzxvphotsyfpcbkd.mp4':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      encoder         : Lavf56.15.102
      Stream #0:0(und): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default)
      Metadata:
        handler_name    : VideoHandler
        encoder         : Lavc56.13.100 libx264
      Stream #0:1(und): Audio: mp3 (libmp3lame) (i[0][0][0] / 0x0069), 48000 Hz, stereo, fltp (default)
      Metadata:
        handler_name    : SoundHandler
        encoder         : Lavc56.13.100 libmp3lame
  Stream mapping:
    Stream #0:0 -&gt; #0:0 (h264 (native) -&gt; h264 (libx264))
    Stream #0:1 -&gt; #0:1 (aac (native) -&gt; mp3 (libmp3lame))
  Press [q] to stop, [?] for help
  frame=   31 fps=0.0 q=0.0 size=       0kB time=00:00:01.05 bitrate=   0.4kbits/s dup=1 drop=0frame=   46 fps= 41 q=0.0 size=       0kB time=00:00:01.56 bitrate=   0.2kbits/s dup=1 drop=0frame=   52 fps= 32 q=29.0 size=     149kB time=00:00:01.75 bitrate= 698.4kbits/s dup=1 drop=frame=   64 fps= 28 q=29.0 size=     258kB time=00:00:02.16 bitrate= 977.2kbits/s dup=1 drop=frame=   74 fps= 26 q=29.0 size=     389kB   
  video:39673kB audio:211kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.143487%
  [libx264 @ 0x1e903a0] frame I:27    Avg QP:18.78  size: 58834
  [libx264 @ 0x1e903a0] frame P:2202  Avg QP:23.67  size: 14187
  [libx264 @ 0x1e903a0] frame B:2323  Avg QP:25.75  size:  3356
  [libx264 @ 0x1e903a0] consecutive B-frames: 24.7% 18.7%  9.0% 47.5%
  [libx264 @ 0x1e903a0] mb I  I16..4: 18.8% 74.7%  6.5%
  [libx264 @ 0x1e903a0] mb P  I16..4:  2.1%  5.0%  0.3%  P16..4: 22.2%  6.0%  1.9%  0.0%  0.0%    skip:62.5%
  [libx264 @ 0x1e903a0] mb B  I16..4:  0.1%  0.3%  0.0%  B16..8: 19.9%  1.0%  0.1%  direct: 0.3%  skip:78.3%  L0:42.3% L1:55.3% BI: 2.4%
  [libx264 @ 0x1e903a0] 8x8 transform intra:68.2% inter:86.5%
  [libx264 @ 0x1e903a0] coded y,uvDC,uvAC intra: 35.8% 52.3% 4.5% inter: 5.2% 7.4% 0.0%
  [libx264 @ 0x1e903a0] i16 v,h,dc,p: 28% 23%  8% 40%
  [libx264 @ 0x1e903a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 27% 20% 22%  3%  6%  6%  7%  5%  4%
  [libx264 @ 0x1e903a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 21% 14%  4%  8%  7%  7%  4%  3%
  [libx264 @ 0x1e903a0] i8c dc,h,v,p: 56% 18% 20%  6%
  [libx264 @ 0x1e903a0] Weighted P-Frames: Y:0.9% UV:0.2%
  [libx264 @ 0x1e903a0] ref P L0: 73.4% 13.0% 10.0%  3.6%  0.0%
  [libx264 @ 0x1e903a0] ref B L0: 92.2%  6.7%  1.1%
  [libx264 @ 0x1e903a0] ref B L1: 96.6%  3.4%
  [libx264 @ 0x1e903a0] kb/s:2139.74
  </code></pre>
  
  <p>End Edit</p>
  
  <p>I know this should work since the exact line does work for other files. But the result with these is a silent video.</p>
  
  <p>I checked the audio file being used and it seemed fine when played. but I did get a weird warning when creating it. Basically I have 2 audio tracks, one is overlay music and the other is talking. I create the combined audio with this command.</p>
  
  <pre><code>ffmpeg -y -i /var/www/temp/audioTrack.mp3 -i /var/www/temp/musicTrack.mp3 -filter_complex amerge -c:a libmp3lame -q:a 4 /var/www/temp/combined.mp3
  </code></pre>
  
  <p>Here is the output from the second command.</p>
  
  <pre><code>ffmpeg version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2000-2016 the FFmpeg developers
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
    libavutil      54. 15.100 / 54. 15.100
    libavcodec     56. 13.100 / 56. 13.100
    libavformat    56. 15.102 / 56. 15.102
    libavdevice    56.  3.100 / 56.  3.100
    libavfilter     5.  2.103 /  5.  2.103
    libavresample   2.  1.  0 /  2.  1.  0
    libswscale      3.  1.101 /  3.  1.101
    libswresample   1.  1.100 /  1.  1.100
    libpostproc    53.  3.100 / 53.  3.100
  Input #0, mp3, from '/var/www/temp/audioTrack.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.89, start: 0.025057, bitrate: 128 kb/s
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
      Metadata:
        encoder         : Lavc56.13
  Input #1, mp3, from '/var/www/temp/musicTrack.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.89, start: 0.025057, bitrate: 128 kb/s
      Stream #1:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
      Metadata:
        encoder         : Lavc56.13
  [Parsed_amerge_0 @ 0x15e3760] No channel layout for input 1
  [Parsed_amerge_0 @ 0x15e3760] Input channel layouts overlap: output layout will be determined by the number of distinct input channels
  Output #0, mp3, to '/var/www/temp/combined.mp3':
    Metadata:
      TSSE            : Lavf56.15.102
      Stream #0:0: Audio: mp3 (libmp3lame), 44100 Hz, stereo, s16p (default)
      Metadata:
        encoder         : Lavc56.13.100 libmp3lame
  Stream mapping:
    Stream #0:0 (mp3) -&gt; amerge:in0
    Stream #1:0 (mp3) -&gt; amerge:in1
    amerge -&gt; Stream #0:0 (libmp3lame)
  Press [q] to stop, [?] for help
  [libmp3lame @ 0x1601000] Trying to remove 1152 samples, but the queue is empty
  size=    2001kB time=00:02:08.88 bitrate= 127.2kbits/s    
  video:0kB audio:2001kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.012350%
  </code></pre>
  
  <p>Of note is these sections (I believe).</p>
  
  <pre><code>[Parsed_amerge_0 @ 0x15e3760] No channel layout for input 1
  [Parsed_amerge_0 @ 0x15e3760] Input channel layouts overlap: output layout will be determined by the number of distinct input channels
  </code></pre>
  
  <p>and</p>
  
  <pre><code>[libmp3lame @ 0x1601000] Trying to remove 1152 samples, but the queue is empty
  </code></pre>
  
  <p>As I said the output audio file sounds correct.</p>
  
  <p>The Music and Audio tracks are created with AudioSegment in python from the pydub library. I've used this before with no issues. The code for this is as follows.</p>
  
  <pre><code>sound = AudioSegment.from_mp3(audio)
  introSilence = AudioSegment.silent(duration=introLength)
  creditsSilence = AudioSegment.silent(duration=creditsLength)
  increasedAudio = sound + 12
  talking = introSilence + increasedAudio + creditsSilence
  talking.export(audioTrack, format="mp3")
  mus = AudioSegment.from_mp3(music)
  introMusic = mus[ : introLength]
  videoMusic = mus[introLength - crossFade : introLength + videoLength + crossFade]
  creditsMusic = mus[totalLength - creditsLength : totalLength]
  lowerMusic = videoMusic - 6
  totalMusic = introMusic.append(lowerMusic, crossfade=crossFade).append(creditsMusic, crossfade=crossFade).fade_out(fadeOut)
  totalMusic.export(musicTrack, format="mp3")
  </code></pre>
  
  <p>Here is the output of <code>ffprobe</code> on the 2 audio files.</p>
  
  <p>for audioTrack</p>
  
  <pre><code>ffprobe version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2007-2016 the FFmpeg developers
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
    libavutil      54. 15.100 / 54. 15.100
    libavcodec     56. 13.100 / 56. 13.100
    libavformat    56. 15.102 / 56. 15.102
    libavdevice    56.  3.100 / 56.  3.100
    libavfilter     5.  2.103 /  5.  2.103
    libavresample   2.  1.  0 /  2.  1.  0
    libswscale      3.  1.101 /  3.  1.101
    libswresample   1.  1.100 /  1.  1.100
    libpostproc    53.  3.100 / 53.  3.100
  Input #0, mp3, from 'temp/audioTrack.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.89, start: 0.025057, bitrate: 128 kb/s
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
      Metadata:
        encoder         : Lavc56.13
  </code></pre>
  
  <p>and for musicTrack</p>
  
  <pre><code>ffprobe version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2007-2016 the FFmpeg developers
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
    libavutil      54. 15.100 / 54. 15.100
    libavcodec     56. 13.100 / 56. 13.100
    libavformat    56. 15.102 / 56. 15.102
    libavdevice    56.  3.100 / 56.  3.100
    libavfilter     5.  2.103 /  5.  2.103
    libavresample   2.  1.  0 /  2.  1.  0
    libswscale      3.  1.101 /  3.  1.101
    libswresample   1.  1.100 /  1.  1.100
    libpostproc    53.  3.100 / 53.  3.100
  Input #0, mp3, from 'temp/musicTrack.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.89, start: 0.025057, bitrate: 128 kb/s
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
      Metadata:
        encoder         : Lavc56.13
  </code></pre>
  
  <p>I can't see any issues with these.</p>
  
  <p>For completeness here is the ffprobe result for the combined audio track.</p>
  
  <pre><code>ffprobe version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2007-2016 the FFmpeg developers
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
    libavutil      54. 15.100 / 54. 15.100
    libavcodec     56. 13.100 / 56. 13.100
    libavformat    56. 15.102 / 56. 15.102
    libavdevice    56.  3.100 / 56.  3.100
    libavfilter     5.  2.103 /  5.  2.103
    libavresample   2.  1.  0 /  2.  1.  0
    libswscale      3.  1.101 /  3.  1.101
    libswresample   1.  1.100 /  1.  1.100
    libpostproc    53.  3.100 / 53.  3.100
  Input #0, mp3, from 'temp/combined.mp3':
    Metadata:
      encoder         : Lavf56.15.102
    Duration: 00:02:08.91, start: 0.025057, bitrate: 127 kb/s
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 127 kb/s
      Metadata:
        encoder         : Lavc56.13
  </code></pre>
  
  <p>Any help would be much appreciated.</p>
  
  <p>Thanks,</p>
  
  <p>Stu.</p>