[FFmpeg-user] Bug in FFMPEG Alsa?

christina zou zou.christina at gmail.com
Sat Feb 18 03:38:16 EET 2017

Hi Carl (and all),

Well, I can't remove the -acodec pcm_s32le option. If I just run:

ffmpeg -f alsa -i mic_sv temp.wav

'[alsa @ 0x243b3f0] cannot set sample format 0x10000 2 (Invalid argument)
mic_sv: Input/output error'

> Next step will be to copy the options used for arecord.
I already made sure the arecord and ffmpeg PCM options are identical. I
have just written a custom ALSA hook ('michooks') in ffmpeg that dumps all
the PCM settings. Here is the result:

1. arecord -v -r48000 -c2 -fS32_LE --period-size=16384
--buffer-size=65536 -Dmic_sv -twav /dev/null

Uses 5% CPU. Console output:  http://vpaste.net/CPk3A

2. ALSA_CONFIG_PATH=/usr/share/alsa/alsa.conf:./dumpasoundrc ffmpeg -f
alsa -acodec pcm_s32le -i michooks -f  null -

Uses 95% CPU. Console output: http://vpaste.net/xSvae

You can see that I've configured arecord/FFMPEG to have identical
settings (buffer sizes, period sizes, etc.)

Any thoughts? Thank you,


On Fri, Feb 17, 2017 at 3:43 AM, Carl Eugen Hoyos <ceffmpeg at gmail.com>

> 2017-02-17 12:19 GMT+01:00 christina zou <zou.christina at gmail.com>:
> > Hi Carl,
> >
> > Thanks for the quick reply!!
> >
> > My mic natively records in 32bit LE format. I thought -acodec
> > pcm_s32le was merely supplying the input format?
> You are right and it seems to work here but since you are reporting an
> issue I would suggest to try with default values first.
> Carl Eugen
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user
> To unsubscribe, visit link above, or email
> ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".

More information about the ffmpeg-user mailing list