Uso de FFmpeg para asignar Prores Monotracks a una salida de onda estéreo

Así que tengo una fuente de prores que quiero extraer las 2 primeras pistas mono y combinarlas en una salida estéreo. ¿Alguien aquí sabe cómo puedo usar las funciones de mapa y combinación para esto?

 Stream #0:0(eng): Video: prores (apch / 0x68637061), yuv422p10le(bt709, progressive), 1920x1080, 166675 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      encoder         : Apple ProRes 422 (HQ)
      timecode        : 00:00:00:00
    Stream #0:1(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:2(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:3(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:4(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (LFE), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:5(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:6(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:7(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:8(eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:9(eng): Data: none (tmcd / 0x64636D74) (default)
    Metadata:
      creation_time   : 2017-08-14T14:58:35.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00

Utilizar

ffmpeg -i in.mov -af [0:a:0][0:a:1]amerge out.wav