19 Apr
2020
19 Apr
'20
1:18 p.m.
On Sun, 19 Apr 2020 01:48:34 +0200 Gerhard Zintel wrote:
Hi again,
On 19/04/2020 00:39, Gerhard Zintel wrote:
Hi Gerhard,
I thought I might need to abort attempts in that direction, as I used
Audacity to export exactly 5 seconds of audio from one of my files and
then used the player program to output a region of that's entire length
to a new file.
First I noticed the new file is much bigger than the file from Audacity
export, but then I saw it's actually exactly (Audacity_file - 44) * 2
so there's still hope.
Thanks a million for all the help. I had a quick look at using Python
to make files from region information lines. It has a wave module
which has 'setpos' and 'tell' methods which work in frames, so I'll
get there one way or another.
--
John.
On 18/04/2020 12:05, John Murphy wrote:
One further remark. The wave header has two length information at byte offset 5 and 41
(see http://www.topherlee.com/software/pcm-tut-wavformat.html). You can use dd like
described
here (https://unix.stackexchange.com/questions/214820/patching-a-binary-with-dd) to
patch
the created file newname.wav afterwards to inject the correct length information.
The length information has to be in binary representation. You could use the method
described here
(https://stackoverflow.com/questions/9955020/how-to-write-integer-to-binary-…)
to get the 4 byte representation of file newname.wav
A lot of shell magic but it seems to work.
If I simply '>' the input, which was
going to aplay, to a file, it's
done in a flash. Unplayable, but the file contains data. Could I write
a header first somehow? Or a container format would be OK.
there are for sure "correct" ways to do it. If you want to use pure bash magic
here you are:
Header of a wave file contains 44 byte. To extract it to a file use:
head -c 44 original.wav > header.bin
Now you can use your file from above (let's call it part.raw) and use:
cat header.bin part.raw > newname.wav
You should be able to play the new file. Be aware that the header is correct
except for the length information. You might fix this with
wavfix (https://github.com/agfline/wavfix). Furthermore if your parts are
not cut at a sample boundary (e.g. a normal wav file is stereo 16
bit per channel thus 4 byte per sample) you will get noise.