title: ffmpeg version 2.6.8 : Stream specifier ':a' in filtergraph description matches no streams
body: <p>I am not getting why this isn't working.. I have tried to get the video streams with [0:v]/[0:1]/[0:v:0] &amp; the audio streams with [0:a]/[0:0]/[0:0:0].
  nothing worked.</p>
  <p>Explaining the inputs:</p>
  <p>1.1st input stream is a video that can be of varying resolution on which the filter adds a padding on to make it 600:480.</p>
  <p>2.2nd input is an overlay png which is already at 5:4 ratio.. just making it 600:480 before it gets overlaid in the filter.</p>
  <p>3.3rd &amp; 4th ones are also videos which I don't care if they get stretched.. n they are getting stretched to 600:480.</p>
  <p>4.so finally there are 3 streams 1 overlaid video 2 stretched videos which needs to be concatenated.</p>
  <p>here's the command :</p>
  <pre><code>ffmpeg 
  -i '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612.mp4' 
  -i '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612_overlay.png' 
  -i '/home/vidinflux/public_html/assets/user/736/video/Lines1.mp4' 
  -i '/home/vidinflux/public_html/assets/user/736/video/Lines11.mp4' 
  -filter_complex
  &quot;[0:v]trim=0:138,setpts=PTS-STARTPTS[v0];[0:a]atrim=0:138,asetpts=PTS-STARTPTS[a0];[v0]scale='gte(iw/ih\,600/480)*600+lt(iw/ih\,600/480)*((480*iw)/ih):lte(iw/ih\,600/480)*480+gt(iw/ih\,600/480)*((600*ih)/iw)',pad='600:480:(600-gte(iw/ih\,600/480)*600-lt(iw/ih\,600/480)*((480*iw)/ih))/2:(480-lte(iw/ih\,600/480)*480-gt(iw/ih\,600/480)*((600*ih)/iw))/2:black'[x];[1:v]scale=600:480[y];[x][y]overlay=0:0[z];[2:v]scale=600:480,setsar=1:1[x0];[3:v]scale=600:480,setsar=1:1[x1];[x0][2:a][z][a0][x1][3:a]concat=n=3:v=1:a=1[v][a]&quot; 
  -map &quot;[v]&quot; 
  -map &quot;[a]&quot; 
  -c:v libx264 
  -shortest /home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612_final.mp4
  </code></pre>
  <p>this is the complete error I am getting :</p>
  <pre><code>Stream specifier ':a' in filtergraph description  [0:v]trim=0:138,setpts=PTS-STARTPTS[v0];[0:a]atrim=0:138,asetpts=PTS-STARTPTS[a0];[v0]scale='gte(iw/ih\,600/480)*600+lt(iw/ih\,600/480)*((480*iw)/ih):lte(iw/ih\,600/480)*480+gt(iw/ih\,600/480)*((600*ih)/iw)',pad='600:480:(600-gte(iw/ih\,600/480)*600-lt(iw/ih\,600/480)*((480*iw)/ih))/2:(480-lte(iw/ih\,600/480)*480-gt(iw/ih\,600/480)*((600*ih)/iw))/2:black'[x];[1:v]scale=600:480[y];[x][y]overlay=0:0[z];[2:v]scale=600:480,setsar=1:1[x0];[3:v]scale=600:480,setsar=1:1[x1];[x0][2:a][z][a0][x1][3:a]concat=n=3:v=1:a=1[v][a] matches no streams.
  </code></pre>
  <p>also there are these warnings:</p>
  <pre><code>[Parsed_setsar_9 @ 0x219fba0] num:den syntax is deprecated, please use num/den or named options instead
  [Parsed_setsar_11 @ 0x21a4840] num:den syntax is deprecated, please use num/den or named options instead
  </code></pre>
  <p>Complete log as requested :</p>
  <pre><code>[root@cloud ~]# ffmpeg -i '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612.mp4' -i '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612_overlay.png' -i '/home/vidinflux/public_html/assets/user/736/video/Lines1.mp4' -i '/home/vidinflux/public_html/assets/user/736/video/Lines11.mp4' -filter_complex \ &quot;[0:v]trim=0:138,setpts=PTS-STARTPTS[v0];[0:a]atrim=0:138,asetpts=PTS-STARTPTS[a0];[v0]scale='gte(iw/ih\,600/480)*600+lt(iw/ih\,600/480)*((480*iw)/ih):lte(iw/ih\,600/480)*480+gt(iw/ih\,600/480)*((600*ih)/iw)',pad='600:480:(600-gte(iw/ih\,600/480)*600-lt(iw/ih\,600/480)*((480*iw)/ih))/2:(480-lte(iw/ih\,600/480)*480-gt(iw/ih\,600/480)*((600*ih)/iw))/2:black'[x];[1:v]scale=600:480[y];[x][y]overlay=0:0[z];[2:v]scale=600:480,setsar=1:1[x0];[3:v]scale=600:480,setsar=1:1[x1];[x0][2:a][z][a0][x1][3:a]concat=n=3:v=1:a=1[v][a]&quot; -map &quot;[v]&quot; -map &quot;[a]&quot; -c:v libx264 -shortest /home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612_final.mp4
  ffmpeg version 2.6.8 Copyright (c) 2000-2016 the FFmpeg developers
    built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-16)
    configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-gnutls --enable-ladspa --enable-libass --enable-libdc1394 --enable-libfaac --enable-nonfree --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
    libavutil      54. 20.100 / 54. 20.100
    libavcodec     56. 26.100 / 56. 26.100
    libavformat    56. 25.101 / 56. 25.101
    libavdevice    56.  4.100 / 56.  4.100
    libavfilter     5. 11.102 /  5. 11.102
    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 '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612.mp4':
    Metadata:
      major_brand     : mp42
      minor_version   : 0
      compatible_brands: isommp42
      creation_time   : 2017-08-21 02:23:24
    Duration: 00:02:17.23, start: 0.000000, bitrate: 417 kb/s
      Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709), 640x360 [SAR 1:1 DAR 16:9], 318 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
      Metadata:
        handler_name    : VideoHandler
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96 kb/s (default)
      Metadata:
        creation_time   : 2017-08-21 02:23:24
        handler_name    : IsoMedia File Produced by Google, 5-11-2011
  Input #1, png_pipe, from '/home/vidinflux/public_html/assets/temp/2018020116464612/2018020116464612_overlay.png':
    Duration: N/A, bitrate: N/A
      Stream #1:0: Video: png, rgba, 600x479, 25 tbr, 25 tbn, 25 tbc
  Input #2, mov,mp4,m4a,3gp,3g2,mj2, from '/home/vidinflux/public_html/assets/user/736/video/Lines1.mp4':
    Metadata:
      major_brand     : mp42
      minor_version   : 1
      compatible_brands: mp41mp42isom
      creation_time   : 2018-01-31 22:40:09
    Duration: 00:00:04.90, start: 0.103811, bitrate: 846 kb/s
      Stream #2:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, smpte170m/bt470bg/bt709), 1920x1080, 827 kb/s, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
      Metadata:
        creation_time   : 2018-01-31 22:40:10
        handler_name    : Core Media Video
  Input #3, mov,mp4,m4a,3gp,3g2,mj2, from '/home/vidinflux/public_html/assets/user/736/video/Lines11.mp4':
    Metadata:
      major_brand     : mp42
      minor_version   : 1
      compatible_brands: mp41mp42isom
      creation_time   : 2018-01-31 22:40:09
    Duration: 00:00:04.90, start: 0.103811, bitrate: 846 kb/s
      Stream #3:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, smpte170m/bt470bg/bt709), 1920x1080, 827 kb/s, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
      Metadata:
        creation_time   : 2018-01-31 22:40:10
        handler_name    : Core Media Video
  [Parsed_setsar_9 @ 0x17c8ba0] num:den syntax is deprecated, please use num/den or named options instead
  [Parsed_setsar_11 @ 0x17cd840] num:den syntax is deprecated, please use num/den or named options instead
  Stream specifier ':a' in filtergraph description  [0:v]trim=0:138,setpts=PTS-STARTPTS[v0];[0:a]atrim=0:138,asetpts=PTS-STARTPTS[a0];[v0]scale='gte(iw/ih\,600/480)*600+lt(iw/ih\,600/480)*((480*iw)/ih):lte(iw/ih\,600/480)*480+gt(iw/ih\,600/480)*((600*ih)/iw)',pad='600:480:(600-gte(iw/ih\,600/480)*600-lt(iw/ih\,600/480)*((480*iw)/ih))/2:(480-lte(iw/ih\,600/480)*480-gt(iw/ih\,600/480)*((600*ih)/iw))/2:black'[x];[1:v]scale=600:480[y];[x][y]overlay=0:0[z];[2:v]scale=600:480,setsar=1:1[x0];[3:v]scale=600:480,setsar=1:1[x1];[x0][2:a][z][a0][x1][3:a]concat=n=3:v=1:a=1[v][a] matches no streams.
  </code></pre>