[FFmpeg-user] Stream specifier ':v' in filtergraph ... matches no streams. (Seeking help on parsing output)

[John Crossman]

Can you help me understand the problem?  (Thanks)

*The command:*

/usr/bin/ffmpeg -i audio.mp2 -i screen.mp4 -filter_complex
[1:v]pad=iw*2:ih[bg];[bg][0:v]overlay=W/2+((W/2-w)/2):(H-h)/2 -qscale:v 2
-strict -2 output.mp4

*The output:*

ffmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  built on May 10 2013 15:14:14 with gcc 4.4.6 (GCC) 20120305 (Red Hat
4.4.6-4)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64
--mandir=/usr/share/man --enable-shared --enable-runtime-cpudetect
--enable-gpl --enable-version3 --enable-postproc --enable-avfilter
--enable-pthreads --enable-x11grab --enable-vdpau --disable-avisynth
--enable-frei0r --enable-libopencv --enable-libdc1394 --enable-libgsm
--enable-libmp3lame --enable-libnut --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp
--enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx
--enable-libx264 --enable-libxavs --enable-libxvid --extra-cflags='-O2 -g
-pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC' --disable-stripping
  libavutil      52. 18.100 / 52. 18.100
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.104 / 54. 63.104
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 42.103 /  3. 42.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[mp3 @ 0x141dbe0] max_analyze_duration 5000000 reached at 5015510
microseconds
[mp3 @ 0x141dbe0] Estimating duration from bitrate, this may be inaccurate
Input #0, mp3, from '/export/mh_data/opencast/shared/workspace/mediapackage/
3d4024ec-6f38-4a46-9505-7c11dffdff8a/aeda9898-4f20-
4eec-a654-a8b18baf106a/audio.mp2':
  Duration: 00:04:59.46, start: 0.000000, bitrate: 192 kb/s
    Stream #0:0: Audio: mp2, 44100 Hz, stereo, s16p, 192 kb/s
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from '/export/mh_data/opencast/
shared/workspace/mediapackage/3d4024ec-6f38-4a46-9505-
7c11dffdff8a/8638cca9-f829-4edf-8020-4443f07c6e72/screen.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf54.63.104
  Duration: 00:04:59.00, start: 0.000000, bitrate: 168 kb/s
    Stream #1:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
1024x768 [SAR 1:1 DAR 4:3], 28 kb/s, 100 fps, 100 tbr, 12800 tbn, 200 tbc
    Metadata:
      handler_name    : VideoHandler
    Stream #1:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo,
fltp, 123 kb/s
    Metadata:
      handler_name    : SoundHandler
Stream specifier ':v' in filtergraph description
[1:v]pad=iw*2:ih[bg];[bg][0:v]overlay=W/2+((W/2-w)/2):(H-h)/2 matches no
streams.