Audacity Forum

All,

I wasn't deliberately intending to test Audacity*, but this is the second time in recent months that I've tried to use it to edit a rather large MP3 file.

By the way, my reason for writing is NOT to report a problem, but rather to report that it works like a charm, even with an extraordinarily large file. In a previous project from last year, the forum seemed surprised that I had been working with an imported MP3 recording that was 12 hours long. I was kind of surprised, too, but perhaps you folks responsible for developing Audacity already knew this was possible.

This time, though, I had a bigger project to work on. The MP3 file was just over 380 MBytes -- yes, you read that correctly -- and the length of the recording is -- get this -- 35 hours, 31 minutes long. I kid you not! When I opened the file for the first time, since I had no info regarding the time/length of the recording, I opened it for the first time using VLC Media Player. I didn't believe what I was seeing, so I also tried to open this huge MP3 file in Sony Sound Forge, Audacity, and WinAmp, but all these programs indicated the same 35-hour-plus length.

My suggestion: Don't edit files this big with just 2 GBytes of RAM. Although I made just one modest edit, I decided to save the project just to be sure it would work; it took 6 minutes to save the project, but by saying that, I'm surely not complaining. Interestingly, although the MP3 file I imported was 380 MBytes, after the one minor test edit I made, I observed that the AUP file was 900 KBytes with a Data directory having the following properties: 5,861 files in 24 sub-directories, consuming 5.8 GBytes of disk space. Is that normal? Does that surprise Audacity's developers?

Closing this project was easy/fast and re-opening it took just a second or so. I happily noticed the project opened with Audacity displaying the portion of the time-line where I had last been working on the project, and the display had zoomed-in just as I had been when I closed the project.

Simply beautiful! I think it's time to make another donation. I really like using Audacity and expressing my appreciation is the least I can do. Thank you all very much!

Tony M.

* System Info: I'm using version 1.3.14-beta (build date Dec 8, 2011) on a Windows Vista Home Premium system with 2 GBytes of RAM

I think that you're very close to the limit of what Audacity Projects can currently handle.
The quoted limit is 2,147,483,648 samples (about 12 hours of CD quality audio). If an Audacity Project has more samples than that, Audacity can "loose count" of the samples and then cannot open the project correctly.

TonyVA408 wrote:after the one minor test edit I made, I observed that the AUP file was 900 KBytes with a Data directory having the following properties: 5,861 files in 24 sub-directories, consuming 5.8 GBytes of disk space. Is that normal?

That sounds about right.
Audacity always works with uncompressed audio data, so when your 380 MB MP3 is de-compressed, that will create around 4 GB of data (depending on the MP3 compression settings). When you perform an operation on the audio, Audacity will copy data as required so that the operation can be undone if you so choose.
The .AUP file keeps a record of the audio in blocks that are usually about 1 MB, so that's your 5,861 files. If the MP3 is stereo, then that will be around 12,000 lines of text in the .AUP file, so 900 KB is a bit bigger than I would have expected, but not massively so.

TonyVA408 wrote:My suggestion: Don't edit files this big with just 2 GBytes of RAM.

Good advice, though I'd recommend not editing files that big, even if you have loads of RAM. Much of the "load" when dealing with very large files is in reading/writing to disk, and that will be slow even on a blazingly fast computer.

Steve,

Good day and thank you for your reply, Steve.

I just wanted to add one thing. I forgot to mention where I could possibly be getting audio files as large as I described. In case anyone's curious, there's a university archive department I occasionally deal with and they conduct phone interviews with distinguished contributors. In both cases, the 12-hour and the 35-hour MP3 files represent a series of telephone interviews conducted over several days, and the university just strings them all together, creating these monstrous MP3 files I mentioned. The bit rates are just 24 kbps, by the way.

Thank you again, Steve, and please pass along my sincere compliments to the whole Audacity Team.

Tony M.

TonyVA408 wrote: The bit rates are just 24 kbps,

Which will have a fairly low sample rate, and thus explains how you are able to successfully handle over 12 hours.

What I would probably do with such monstrous MP3s is to use "MP3directCut" or "MP3split" to split the MP3 into more manageable size chunks. Both of these programs are free, and both can split MP3s losslessly (no loss of sound quality).

What I would probably do with such monstrous MP3s is to use "MP3directCut" or "MP3split" to split the MP3 into more manageable size chunks. Both of these programs are free, and both can split MP3s losslessly (no loss of sound quality).

Besides avoiding the 2nd lossy encode, you save the time it takes to de-compress and re-compress the file. And, you are directly working on a smaller file so disc read/writes don't take as long.

These tools can't do advanced editing/processing/effects that you can do with a regular audio editor (like Audacity), but they can cut, splice, and change volume.

Hi, steve.

regarding your previous post, which is

"What I would probably do with such monstrous MP3s is to use "MP3directCut" or "MP3split" to split the MP3 into more manageable size chunks. Both of these programs are free, and both can split MP3s losslessly (no loss of sound quality)."

i'm exploring this software to split a huge mp3 file which is 64.1MB in size, approximate to 70 minutes in time. How can i use the Audacity software to split the mp3 file? i've tried using edit-->clip boundaries-->split/split new,but it still failed. can you help me with this?

hope a positive reply from you soon

azrinshafina wrote: i'm exploring this software to split a huge mp3 file which is 64.1MB in size, approximate to 70 minutes in time. How can i use the Audacity software to split the mp3 file?

See here for one way to do it: http://wiki.audacityteam.org/wiki/Split ... ate_tracks