使用ffmpeg从视频文件中提取音频流并输出到单个立体声WAV文件

Question

I've been trying for a few hours to get the right arguments to do the below operation with ffmpeg, but i'm a bit out of my depth. If anyone can give me some guidance, that would be very helpful.

Input file is MXF with one video track and two separate 48k 24b PCM audio tracks. I want to extract just the audio, map first track to left, second track to right and output as a stereo wave file.

I am trying variations on the below command, but it seems to be unhappy about the video stream, giving the error

"mapchan: stream #0.0 is not an audio stream."

ffmpeg -i test2.mxf -vn -map_channel 0.0.1 output.wav_CH0 -map_channel 0.0.2 output.wav_CH1

Here is ffmpeg's analysis of the streams in case it is helpful:

    Stream #1:0: Video: mpeg2video (4:2:2), yuv422p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], max. 50000 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
Stream #1:1: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:2: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:3: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:4: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:5: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:6: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:7: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s
Stream #1:8: Audio: pcm_s24le, 48000 Hz, mono, s32, 1152 kb/s

Answer 1

The filtergraph function seems to do the trick.

ffmpeg -i test2.mxf -filter_complex "[0:1:0][0:2:0]amerge=inputs=2[aout]" -map "[aout]" output.wav

The 0:1:0 seems to represent input1 (the -i option), stream1 (the track), channel (left/right if it were stereo). --could be wrong with my interpretation here, but it works nonetheless.

ffmpeg documentation and FFmpeg Wiki: Audio Channel Manipulation were very helpful.