[FFmpeg-user] How to get only audio from "rawvideo" stream

[Deron]

I'm trying to generate a number of HLS streams from a single source 
including using the new webvtt for cc.

The following command:

ffmpeg -i test.ts -vn -f hls -hls_segment_filename "a.%d.ts" -y "a.m3u8"

Works as expected, but

ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -vn -sn -f hls 
-hls_segment_filename "a.%d.ts" -y "a.m3u8"

Fails with:

ffmpeg version N-70148-g418be7c Copyright (c) 2000-2015 the FFmpeg 
developers
   built with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
   configuration: --enable-shared --enable-gpl --enable-nonfree 
--enable-libxvid --enable-libx264 --enable-libmp3lame --enable-libvorbis 
--enable-libfaac --enable-libopenjpeg
   libavutil      54. 19.100 / 54. 19.100
   libavcodec     56. 26.100 / 56. 26.100
   libavformat    56. 23.104 / 56. 23.104
   libavdevice    56.  4.100 / 56.  4.100
   libavfilter     5. 11.101 /  5. 11.101
   libswscale      3.  1.101 /  3.  1.101
   libswresample   1.  1.100 /  1.  1.100
   libpostproc    53.  3.100 / 53.  3.100
[mpeg2video @ 0x1c777a0] Invalid frame dimensions 0x0.
     Last message repeated 35 times
Input #0, lavfi, from 'movie=test.ts[out0+subcc]':
   Duration: N/A, start: 9602.931211, bitrate: N/A
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 
1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc
     Stream #0:1: Subtitle: eia_608
Output #0, hls, to 'a.m3u8':
Output file #0 does not contain any stream

I get that I surpressed the video stream, and the audio is merged with 
it. How do I get it out without changing the input? I ultimately need to 
generate multiple streams including cc from a single input, so I can't 
remove cc from the input.

Thanks,

Deron