[FFmpeg-user] down sampling

Carl Eugen Hoyos ceffmpeg at gmail.com
Fri Dec 28 12:57:39 EET 2018

2018-12-28 11:32 GMT+01:00, Michael Koch <astroelectronic at t-online.de>:
> Am 28.12.2018 um 10:18 schrieb Carl Eugen Hoyos:
>> 2018-12-28 10:14 GMT+01:00, Michael Koch <astroelectronic at t-online.de>:
>>> Am 28.12.2018 um 00:50 schrieb Moritz Barsnick:
>>>> On Thu, Dec 27, 2018 at 20:29:34 +0100, Michael Koch wrote:
>>>>> I think the bigger problem is "outputting through the computers
>>>>> speakers". As far as I know it depends on the operating system, and
>>>>> under Windows it's impossible.
>>>> You can always pipe to ffplay, which plays audio also under Windows
>>>> (using SDL audio).
>>> I did try that some time ago, without success.
>> What did you try? (Command line and complete, uncut console output
>> missing.)
> Below is the console output. It's an ultrasonic converter and it works
> fine when I send the output to a file.
> F:\Sound\Ultraschall_Konvertierung>c://ffmpeg/ffmpeg -f dshow -channels
> 2 -i aud
> io="Mikrofon (Realtek High Definiti" -f lavfi -i
> aevalsrc="sin(3000*2*PI*t):c=st
> ereo:s=44100" -filter_complex
> "[0]volume=3,highpass=f=3000,highpass=f=3000,highp
> ass=f=3000,highpass=f=3000[sound];[sound][1]amultiply,lowpass=f=10000,lowpass=f=

> 10000,lowpass=f=10000,lowpass=f=10000" -t 10 -f mp3 pipe:play -
> //ffmpeg/ffplay

The syntax looks broken here:
Do you want to use a named pipe "play"?
Iiuc, you have to create this pipe before launching FFmpeg,
no need to specify a second output url.

Or you want to use the pipe "-", in this case I believe you do
not consume it with your ffplay command:

> -i pipe:play

Finally, I would expect that you have to separate the call
to ffmpeg from the call to ffplay: "|"

Carl Eugen

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