asplit does not work for unknown channel layouts

[Carl Eugen Hoyos]

​http://thread.gmane.org/gmane.comp.video.ffmpeg.user/61019
Unknown channel layouts used to work fine with asplit until d300f5f6f570659e4b58567b35c9e8600c9f2956

$ ffmpeg -loglevel 99 -f s16le -ac 10 -i /dev/zero -filter_complex asplit[a1][a2] -map [a1] -f null -t 1 - -map "[a2]" -f null -t 1 -
ffmpeg version N-78307-gf89bc66 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --enable-libmp3lame
  libavutil      55. 17.100 / 55. 17.100
  libavcodec     57. 24.101 / 57. 24.101
  libavformat    57. 24.100 / 57. 24.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 28.100 /  6. 28.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Splitting the commandline.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument '99'.
Reading option '-f' ... matched as option 'f' (force format) with argument 's16le'.
Reading option '-ac' ... matched as option 'ac' (set number of audio channels) with argument '10'.
Reading option '-i' ... matched as input file with argument '/dev/zero'.
Reading option '-filter_complex' ... matched as option 'filter_complex' (create a complex filtergraph) with argument 'asplit[a1][a2]'.
Reading option '-map' ... matched as option 'map' (set input stream mapping) with argument '[a1]'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'null'.
Reading option '-t' ... matched as option 't' (record or transcode "duration" seconds of audio/video) with argument '1'.
Reading option '-' ... matched as output file.
Reading option '-map' ... matched as option 'map' (set input stream mapping) with argument '[a2]'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'null'.
Reading option '-t' ... matched as option 't' (record or transcode "duration" seconds of audio/video) with argument '1'.
Reading option '-' ... matched as output file.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument 99.
Applying option filter_complex (create a complex filtergraph) with argument asplit[a1][a2].
Successfully parsed a group of options.
Parsing a group of options: input file /dev/zero.
Applying option f (force format) with argument s16le.
Applying option ac (set number of audio channels) with argument 10.
Successfully parsed a group of options.
Opening an input file: /dev/zero.
[file @ 0x2cde060] Setting default whitelist 'file'
[s16le @ 0x2cdd7a0] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0
[s16le @ 0x2cdd7a0] All info found
[s16le @ 0x2cdd7a0] 0: start_time: -9223372036854.775 duration: -9223372036854.775
[s16le @ 0x2cdd7a0] stream: start_time: -9223372036854.775 duration: -9223372036854.775 bitrate=7056 kb/s
[s16le @ 0x2cdd7a0] After avformat_find_stream_info() pos: 1024000 bytes read:1048576 seeks:0 frames:50
Input #0, s16le, from '/dev/zero':
  Duration: N/A, bitrate: 7056 kb/s
    Stream #0:0, 50, 1/44100: Audio: pcm_s16le, 44100 Hz, 10 channels, s16, 7056 kb/s
Successfully opened the file.
detected 8 logical cores
Parsing a group of options: output file -.
Applying option map (set input stream mapping) with argument [a1].
Applying option f (force format) with argument null.
Applying option t (record or transcode "duration" seconds of audio/video) with argument 1.
Successfully parsed a group of options.
Opening an output file: -.
Successfully opened the file.
Parsing a group of options: output file -.
Applying option map (set input stream mapping) with argument [a2].
Applying option f (force format) with argument null.
Applying option t (record or transcode "duration" seconds of audio/video) with argument 1.
Successfully parsed a group of options.
Opening an output file: -.
Successfully opened the file.
[graph 0 input from stream 0:0 @ 0x2deaa20] Setting 'time_base' to value '1/44100'
[graph 0 input from stream 0:0 @ 0x2deaa20] Setting 'sample_rate' to value '44100'
[graph 0 input from stream 0:0 @ 0x2deaa20] Setting 'sample_fmt' to value 's16'
[graph 0 input from stream 0:0 @ 0x2deaa20] Setting 'channels' to value '10'
[graph 0 input from stream 0:0 @ 0x2deaa20] tb:1/44100 samplefmt:s16 samplerate:44100 chlayout:(null)
[audio format for output stream 1:0 @ 0x2deb1c0] Setting 'sample_fmts' to value 's16'
[audio format for output stream 0:0 @ 0x2dead60] Setting 'sample_fmts' to value 's16'
[Parsed_asplit_0 @ 0x2dea4c0] auto-inserting filter 'auto-inserted resampler 0' between the filter 'graph 0 input from stream 0:0' and the filter 'Parsed_asplit_0'
[AVFilterGraph @ 0x2de6cc0] query_formats: 8 queried, 19 merged, 3 already done, 0 delayed
[auto-inserted resampler 0 @ 0x2dee540] Cannot select channel layout for the link between filters auto-inserted resampler 0 and Parsed_asplit_0.
[auto-inserted resampler 0 @ 0x2dee540] Unknown channel layouts not supported, try specifying a channel layout using 'aformat=channel_layouts=something'.
Error configuring complex filters.
Invalid argument
[AVIOContext @ 0x2ce6320] Statistics: 1048576 bytes read, 0 seeks

[Elon Musk]

Fixed in b1fe794033c8d781ddafe819141ce6b60d9c7633.