Freesound Project

The answer is NOT straightforward.

With the process I mentioned on my post, the sounds are converted from the original format (say, WAV) to RAW.
This means that some important info is lost in the process, such as bit depth and sample rate. Even a sound editor will require you to supply this information manually if you load it up again.

The same applies to a graphics program importing RAW files: user needs to provide some parameters to the program so it can make sense of the data.

To answer your question.
Even the the exact same RAW file can be made to look quite different when imported as a picture - this because the RAW format file contains no indicators which will allow the graphics program to make sense of the data. Therefore, it will ask the user to provide image widht, heigh, bit depth and "colour encoding" (there are different standards:black&white, RGB, Luma/Chroma,...). Enter different parameters and you get different images.

For a sound made up of a simple constant waveform, you should obtain an image that clearly shows a "pattern". Especially if imported as a black and white picture. When I am at home later I will try to upload some pictures which illustrate what I am talking about.
The patterns can be less obvious for complex sounds (e.g. piano). And you may be unable to obtain a pattern from less harmonic sounds such as a cymbal or speech.

By the way, if anyone uses VST plugins and wants to explore further the image to sound conversion and vice-versa, the KVR Dec plugin competition is now on. Some of the entries are VST plugnis that do precisely these conversions.
Due to interference from the day job , I have not tried these VSTs yet, but anyone can download them for free. Have a look at
http://www.kvraudio.com/developer_challenge_2009.php

This conversation has obviously enticed me to go back and create some noise using these processes.
Will be posting the results with the tag "image-to-sound" on Freesound. Expect some uploads after the weekend...

Yes of course, makes sense. I had some fun trying to get a Blender 'Wood' texture (basically a series of black and white wavy lines, with some minor noise) to audio, but GIMP wouldn't allow me to use 'raw' as extension. Tiff worked rather well, but I do believe bmp should be pretty raw (afaik, it's simply a list of bgr (blue green red) codes in a continuous line), but haven't tried it. Another problem was, while it produced some remarkable sound-like waves, the waves were 'inverted', meaning what's usually the top part of a wave was way at the bottom and the bottom part was at the top. This produced a nasty noise, while the underlying sound was fairly interesting.
I did some experiments in the past converting audio to text (very short samples) and found that for 16 bit samples the center line has hex value 0000, -15 dB(fs) on the plus side has value 16C3, -3 dB on the plus side has value 5A9F, 0 dB on the plus side (max height) is 7FFF and the next number in line, 8000 corresponds to 0 dB (max height) on the minus side, so it completely flips the wave here.
So you have
0000 - 7FFF is center line - 0 dB plus
8000 - FFFF is 0 dB minus - center line

That should mean if you have a black image with a white, blurry line on it, everything that's black is on the center line, where the blurring starts, the wave goes up towards the top. Where the blurry part is 50% grey, the wave hits the top and flip down to the bottom at the next sample. From there it continues up again until full white. From there the blurring starts again back to black, the wave going down towards bottom, where the blurry is grey again, the wave hits bottom and jumps up to the top on next sample. As blurring goes down into black, wave goes back to center line.
In theory! (If I understand correctly) This seems to be correct with my earlier test in mind, the image went from black to white and back a few times, all the time flipping the wave when it hit top or bottom.
I should do some more tests.
And maybe we should do this in a new thread

Hello nemoDaedalus,

Great discussion here. Plenty of things for me to try when I get home!

I know exactly what you mean when you say the waveform is flipped.

Some graphics programs may allow you to "cycle" the colours, so that you can start with a "black picture with a blurry white line on it" and then cycle through the (gryescale). Shifting throug the grayscale like this, you can obtain a file where the soundwave is positioned correctly.

I used to have the same problem of flipped waveforms when I tried to import audio files from the PC into an Amiga computer.

Rather than start a new thread, should we ask one of the moderators to move the thread to a more suitable Forum?
Would you be interested in doing some collaboration on image-to-sound and sound-to-image ?


Cesar / AlienXXX

Yeah, I'm sure the topic can be split?
While I can open anything in Audacity, I couldn't yet get GIMP to open sounds.

[edit]
Heh, this is quite cool. I took the Wood texture from Blender's procedural texture, shifted the shades of grey using Curves, saved the result as bmp and imported the bmp as raw audio in Audacity using settings 16-bit signed, big-endian, mono, 44k1Hz.
The weird line at the beginning of the file you see here is the bmp header. I left it on, but you could easily set a higher start position on import. I did crop the sound after importing.
Note in GIMP how the image is greyscale, but it goes from black to a light grey. It doesn't go up all the way to white. Due to this, there was a bit of negative bias on the wav. I corrected this later.
The resulting wav is uploaded and now awaiting moderation.



[/edit]

OK, great.

I am assuming once the sound is approved you will be posting the link.
May I suggest you do so in a new post in a more appropriate forum and also post the link to this initial discussion?

We will continue the discussion in the new thread and I will be posting my sonic (miss)adventures on the new thread as well.

With regards to the blip cause by the bmp header, I had the same problem too. I mean ultimately, you can import ANY kind of file as a RAW file... Even if you have to manually edit the file name to change it from bmp or GIF or whatever to RAW.
The problem is that you do get the file header. You can edit it out, but the problem is that it is not exactly obvious where the header finishes when you are looking at a sound file on a graphics editor or at a picture on a sound editor...
That is why I prefer to actually convert to RAW format - absolutely no header data at all.

On another matter, you are using GIMP. Are you working on a Linux machine?
I have not installed Audacity, but I have heard great things about this program, so I might install it in th enear future.

Moderator's note: This line of thought is continued in this thread.