audio impossible?

[marcorocchini]

Hi,
considering my usual: https://dl.dropboxusercontent.com/u/39871584/C0020.mxf

I would like generate a first .wav file (16bit 48Khz L+R) with audio Ch1 e Ch2

and a second .wav file (16bit 48Khz L+R) with audio Ch3 e Ch4



I have try ffmpeg -i C0020.mxf -map_channel 0.1.0 -map_channel 0.2.0 -af "volume=9dBrecision=fixed" audioch1ch2.wav

but I error something.. I get a mono .wav with only ch1

Is it possible? thanks

ps: in original file audio ch1 is mute, audio ch2 panoramic mic camera, audio ch3=ch4 (otherMic)

[poisondeathray]

Try it with amerge

ffmpeg -i c0020.mxf -filter_complex "[0:1] [0:2] amerge" -c:a pcm_s16le output1.wav
ffmpeg -i c0020.mxf -filter_complex "[0:3] [0:4] amerge" -c:a pcm_s16le output2.wav

[marcorocchini]

mm it does work!

only one thing: can I amplify of +9dB?

[poisondeathray]

I don't think ffmpeg audio filters work in dB, just a multiplier
https://www.ffmpeg.org/ffmpeg-filters.html#volume

eg

ffmpeg -i c0020.mxf -filter_complex "[0:1] [0:2] amerge,volume=2" -c:a pcm_s16le test.wav

You have to adjust the value . If you need dB scale, maybe pipe it to sox

[marcorocchini]

NONONOsox it's so perfect! thanks