Re: [SoX-users] acoustic-marks in audio-file

[Ulrich K. <ul...@ch...>]

"Rainer M. Engel" <en...@en...>:

> I want to create a soundfile in which I hear at certain time positions a
> very short peep-sound. This file should be mixed over the audio track of
> a movie to mark some positions in an acoustic manner.
>
> Layout:
> |-silent----------------|peep|-silent------------| ....
>  mixed with..
> |-original-audio---------------------------------| ....
>
>
> What would be the best way to achieve this?
>
> Given is a wav-file 48KHz Stereo of ~2hours length and there would be a
> few or several hundred peep marks to make.

The mixing can be done with
   sox -M input.wav beeps-and-silence.wav output.wav remix -m 1,3 2,3

The easiest way to place the beeps is probably to replicate them into  
as many channels as you'll need beeps, then move them with "delay",  
like this:
   sox beep.wav beeps-and-silence.wav remix 1 1 1 1 1 1 1 ... 1 delay  
2:17 3:51 47:11 ... 1:58:22 remix -m -
However, this is not very efficient (for a large number of beeps)  
because of the many temporary channels. It may also need increasing  
the buffer size.

A more efficient approach would be to use repeat and pad, operating on  
only one channel. However, the beep positions would need some  
preprocessing.

> 1. create all silent fragments in their desired length
> 2. create peep-wave segment (perhaps: reference level tone)
> 3. concatenate these fragments: silent1+peep+silent2+peep ...

This is also possible. You'd need to preprocess the positions here,  
too, however, and you'd have many temporary files.

Ulrich