Plot very large audio files

Hello!

I need to display very large audio files (WAV PCM, Mono, > 1 GB) in a MATLAB figure. The problem is: These audio files are too large to load the whole file into memory at once ("OUT OF MEMORY" errors).

I want to be able to see the amplitude over time, and it should be possible to zoom in and out and to do selections, just like it is in regular audio software (e.g. Adobe Audition):

So when zooming in, it should read parts of the WAV-file to update the figure. I also need to to get the absolute sample number of the current selection shown in the figure.

The closest I found was this ("Simple Audio Editor" on File Exchange):

However, it reads the whole WAV-file, and therefore it is unsuitable for large audio data.

Could you give me a hint on how to achieve what I want?

Answer 1

[Daniel Shub]

Why not just get more RAM, 1 GB isn't that big. Otherwise you are either going to have to hack the FEX contribution or write your own. There is no reason you cannot do it. You can read in bits of your sound with the wavread function

doc wavread

The problem is you are going to need to write your own functions for zooming in and out and selections. These functions are going to need to determine what portion of the file needs to be loaded, load it, and store the offset someplace. If the user zooms out too much you are going to run into memory problems. At anything but the lowest hourly rate, you are better off upgrading your hardware.

Answer 2

[Lemar DeSalis]

Oh, I have way more than 1 GB RAM: It's 6 GB on a Win7 x64 machine and 8 GB on another machine, actually. That is still not enough!

Loading a 1 GB WAV-file doesn't mean it only needs 1 GB of RAM! If the WAV-file is at 16 bit precision, and you need to do floating point operations, it will need at least 2 GB memory when using single-represantation, and even 4 GB when using double representation. And to actually plot it, you need a multiple amount of that! The plotting function "dsplot" (downsampled plot) creates 3 copies of the signal and it needs floating point data, so that's at least 8 GB of RAM for a 1 GB WAV-file!

And I need to load TWO large WAV-files at the same time!

Therefore, upgrading RAM is not possible! This has to be done with less memory consumption!