On Sat, May 5, 2018 at 4:43 PM, Måns Rullgård <mans@mansr.com> wrote:

> Shailendra Paliwal <beingshailendra@gmail.com> writes:
>
> > Hello,
> >
> > I found sox as a command-line equivalent of Audacity. I was wondering how
> > can I glitch images like the way I can using Audacity.
> >
> > On audacity the usual modus operandi is,
> >
> >    1. Use Audacity > File > Import > Raw Data, to import a BMP image
> file.
> >    2. Set the encoding to U-Law or A-Law.
> >    3. Apply audio effects to the track.
> >    4. Export Audio, set Save As Type > Other Uncompressed Files
> >    5. Header > RAW (header-less) and Encoding > whichever selected in (2)
> >    6. Rename to BMP
> >
> > I was wondering if the same method can be used with sox. That way I can
> > make shell scripts to glitch images or even thousands of frames in a
> video.
>
> Yes, this can be done.  Try something like this:
>
> $ sox -t ul -c 1 -r 48k input -t ul output effects...
>
This seems to corrupt the header of the file too and then I cannot open it
at all. Usually in Audacity, I would not touch the first 5% of the track
assuming it contains the header information that should be left untouched.

So, I thought if I can split the header and the file contents into two
file. That would be easy to run through sox.

I tried
$ sox -t ul -c 1 -r 48k water.bmp -t ul water_out trim 0 15 : newfile :
restart

This should work because new headers aren't created while spitting and I
checked this by merging these files back (I'm on windows)
$ type water_out* > water_databent.bmp

This get me the image again.

However, I processed one chunk with an audio effect and the file size
reduced drastically from ~700KB to ~2KB. Would you know why did that
happen? I did
$ sox -t ul -c 1 -r 48k water_out002 -t ul water_out002 echo 0.8 0.7 45 0.31

Now the files don't stitch back to the image either.


> --
> Måns Rullgård
>