-filter without specifier fails without explicit error

[Clément Bœsch]

Given a random input file with both audio and video:

☭ ./ffmpeg -f lavfi -i 'testsrc[out0]; aevalsrc=sin(2*PI*t*440)[out1]' -t 5 -y test.avi
ffmpeg version N-47714-g7eafd27 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec 11 2012 03:04:42 with gcc 4.7.2 (GCC)
  configuration: --enable-gpl --enable-fontconfig --enable-libfreetype --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-x11grab --enable-libopenjpeg --enable-libass --enable-libmodplug --enable-libv4l2 --cc=colorgcc --samples=/home/ubitux/fate-samples --prefix=/tmp/ffinstall --enable-runtime-cpudetect --enable-libcelt
  libavutil      52. 12.100 / 52. 12.100
  libavcodec     54. 79.101 / 54. 79.101
  libavformat    54. 49.101 / 54. 49.101
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 26.101 /  3. 26.101
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[lavfi @ 0x2a3b260] Estimating duration from bitrate, this may be inaccurate
Input #0, lavfi, from 'testsrc[out0]; aevalsrc=sin(2*PI*t*440)[out1]':
  Duration: N/A, start: 0.000000, bitrate: 2822 kb/s
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: pcm_f64le, 44100 Hz, mono, dbl, 2822 kb/s
Output #0, avi, to 'test.avi':
  Metadata:
    ISFT            : Lavf54.49.101
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, mono, s32p
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> mpeg4)
  Stream #0:1 -> #0:1 (pcm_f64le -> libmp3lame)
Press [q] to stop, [?] for help
frame=  125 fps=0.0 q=2.0 Lsize=     256kB time=00:00:05.01 bitrate= 418.1kbits/s    
video:199kB audio:39kB subtitle:0 global headers:0kB muxing overhead 7.317413%

...and trying the following commands fail:

☭ ./ffmpeg -i test.avi -filter edgedetect -f null -
ffmpeg version N-47714-g7eafd27 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec 11 2012 03:04:42 with gcc 4.7.2 (GCC)
  configuration: --enable-gpl --enable-fontconfig --enable-libfreetype --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-x11grab --enable-libopenjpeg --enable-libass --enable-libmodplug --enable-libv4l2 --cc=colorgcc --samples=/home/ubitux/fate-samples --prefix=/tmp/ffinstall --enable-runtime-cpudetect --enable-libcelt
  libavutil      52. 12.100 / 52. 12.100
  libavcodec     54. 79.101 / 54. 79.101
  libavformat    54. 49.101 / 54. 49.101
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 26.101 /  3. 26.101
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, avi, from 'test.avi':
  Metadata:
    encoder         : Lavf54.49.101
  Duration: 00:00:05.04, start: 0.000000, bitrate: 415 kb/s
    Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, mono, s16p, 64 kb/s
[buffer @ 0x178f040] Unable to parse option value "0x0" as image size
Error opening filters!

☭ ./ffmpeg -i test.avi -filter volume -f null -
ffmpeg version N-47714-g7eafd27 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec 11 2012 03:04:42 with gcc 4.7.2 (GCC)
  configuration: --enable-gpl --enable-fontconfig --enable-libfreetype --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-x11grab --enable-libopenjpeg --enable-libass --enable-libmodplug --enable-libv4l2 --cc=colorgcc --samples=/home/ubitux/fate-samples --prefix=/tmp/ffinstall --enable-runtime-cpudetect --enable-libcelt
  libavutil      52. 12.100 / 52. 12.100
  libavcodec     54. 79.101 / 54. 79.101
  libavformat    54. 49.101 / 54. 49.101
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 26.101 /  3. 26.101
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, avi, from 'test.avi':
  Metadata:
    encoder         : Lavf54.49.101
  Duration: 00:00:05.04, start: 0.000000, bitrate: 415 kb/s
    Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, mono, s16p, 64 kb/s
[abuffer @ 0x1e057e0] Value inf for parameter 'time_base' out of range [0 - 2.14748e+09]
Error opening filters!

It works fine when using -filter:v or -vf, and -filter:a or -af though. Also note the problem doesn't arise if the input is audio-only or video-only.

We should either fail with a more explicit error when the type specifier is not set, or have better heuristics to guess what the user wants.

[Michael Niedermayer]

Fixed in 640a36a05c4d9d371086c22a158fb3d314a71538