Exporting Large .wav files

[adiant]

I used Audacity to combine two stereo channels, each in their own .wav file, into a new stereo .wav file. Everything appeared to work correctly.

But, when I tried to use the new .wav file, every media player that didn't crash or hang, and Audacity itself, thought the file was 5+ hours long, instead of the 12+ hours long that it is. I checked the file size, and it is 7.5GB, which is about right for a 12 hour 44Kbps stereo .wav file.

I am using Windows XP with SP2, and Audacity 1.2.6.

I am more interested in preventing this from happening in the future than I am in fixing this file, as I have a lot of recordings made this way (off a TASCAM recorder that gives you the stereo tracks separately).

[alatham]

That 7.5GB size sounds just about right, I've never heard of anyone having this problem. Though I doubt too many people go around making 12 hour long wavs.

Hmm... You aren't using the FAT32 file system, are you? The max file size there is 4GB. I'm not sure what would happen if you tried to write a file that big to a hard drive using that setup.

Just to be sure, the method to convert 2 mono wavs to 1 stereo wav is this:

1) Import both Left and Right.

2) Pan Left 100% to the left and Right 100% to the right.

3) Make sure the sample rate in Audacity's lower left hand corner is set how you want. Then File -> Export to Wav. (there's no need to use the "Make Stereo Track" function).

If that's what you did, then replace step 3 with this:

3a) Add several (2 - 4) Markers to the project at points you don't mind splitting the audio (preferably silent portions, if they exist). You can set the cursor normally and press [ctrl]+b to do this. Name each marker "part1", "part2, etc. Now, make sure the sample rate is correct and then File -> Export Multiple. You'll end up with 2 - 4 files that will add up to the whole 12GB file.

Hopefully if you split them up into smaller tracks the media players won't complain. If this isn't acceptable for some reason, let us know.

[adiant]

Unfortunately, with what I'm doing -- historical recording of radio stations -- collectors really do want continuous recordings of 24 and more hours in length. In fact, recordings dating from as early as 1961 try to record a complete 24 hours of a radio station. Even the FCC was paying listeners to make 24 hour recordings of stations in the 1960s, for enforcement purposes. Of course, in those days, amateurs tried to change tapes quickly. And professionals had two recorders and overlapped the recordings. So, there is certainly a need.

With the file in question, I used File-Open to import the Left Channel, and Project-Import Audio, to import the Right channel. Both showed up as Mono. And then, as you guessed, I selected "Make Stereo Track" from the top track's menu.

I did not Pan left or right, but I did File-Export as WAV with 44100 as the Project Rate in the lower left corner. In case it matters, to improve performance, I have set the internal Audacity format to 16-bit 44Kbps, and "Read directly from the original file".

Both my internal hard drive, where Audacity has its Temp files, and my external USB hard drive, where the audio files are stored, are running NTFS.

It looks to me like the header of the .wav file has the wrong length set during the Audacity Export. But I don't know how to verify that theory.

So, I would be very interested in coming up with a way to create very long .wav files with Audacity. I'd prefer not to use the TASCAM to create the stereo .wav file as it is extremely slow -- it takes nearly 12 hours to transfer the left and right channels of a 6 hour recording to an area of its hard drive where I can access them from my computer.

Would you like me to recreate the problem precisely following the instructions below? Or would you like me to figure out how to dump the offending .wav file's headers? Suggestions on the latter would be appreciated, if that is the way that I should go.

[alatham]

Aha!

Check out this wikipedia article on wav files:
http://en.wikipedia.org/wiki/WAV

I'll pull a quote from the "Limitations" section:

The WAV format is limited to files that are less than 4 GB in size, due to its use of a 32 bit unsigned integer to record the file size header

I'm really surprised Audacity didn't warn you of this. I'll post about it in the Adding Features forum in a bit.

So basically, you could only make these files if you're ok with using the 22.05 KHz sample rate (if what you've got is AM radio, this sample rate is good enough to encode all the quality AM radio was capable of).

If you need to use the higher sample rate, you're limited to either using data compression (mp3s, or ogg vorbis), or splitting the files. There is also an uncompressed format called RF64 that can create much longer files. But Audacity cannot output to that at the moment.

Not knowing how you're distributing and/or playing these files, this might be worth nothing, but I don't see a problem with splitting it into "smaller" wav files and just queuing them into a media player to play one after the other.

[adiant]

Thank you for such great info! By my calculation, what Audacity did was write the lower 32-bits of the file size into the WAV fize size header:
in round numbers, real file size is 7.5GB, or 7.5 billion (thousand million in U.K.) bytes. Lower 32 bits of 7.5 billion is 3.2 billion. At 10MB/minute for stereo 44Kbps .wav files, that works out to 5.18 hours, which is how long QuickTime and Audacity say is recorded on my .wav file. RealPlayer hangs and Windows Media Player gives an error.

Obviously, it depends on the Audacity project's definition of bugs, but this sounds more like a bug than a limitation. As you suggest, if all .wav file bigger than 4.3GB resulted in a value of 4.3GB in the .wav file size header field, that might well qualify as a limitation. Clearly, a value of 0.1GB would be the result for a 4.4GB file.

Please let me know if I should fill out a Bug Report.

I should also mention that this size limitation of .wav files probably explains why my TASCAM recorder fails after about 13 hours of continuous recording. It records each stereo track as a separate .wav file.

And, yes, I now have enough information to come up with a solution for storing long recordings.

[13mhz]

hi, i am newbie here and i have a problem with large wav file.
I am recording live gigs on Macintosh PowerBook G3 "Bronze keyboard" using Audacity 1.2.6 .
So far it went good and i was happy with recorded sound files.
But last time i have recorded live 3.55 hours and immediately export it to wav. I went ok, Wav has about 4.5 GB, but when i open it in a player or in Audacity 1.2.6 itself, it only shows me 30 minutes of sound.
What can i do with such a wav file? is it really empty after that 30 mins or there is a way to recover it somehow?
Thanks in advance for any help, this gig is very important to me!

[steve]

Wav has about 4.5 GB, but when i open it in a player or in Audacity 1.2.6 itself, it only shows me 30 minutes of sound.

See previous posts. The maximum file size for WAV files is 4GB. If you try to create WAV files bigger than this they don't work.

[adiant]

Some suggestions from someone who's been there:
(1) save as an Audacity project. I'm not aware of any size/time limitations on that format; OR
(2) save each track separately as WAV. At 44Kbps that gives you over 12.5 hours.

[steve]

At 44Kbps that gives you over 12.5 hours

I think you mean "16 bit 44.1 kHz"

[adiant]

Thanks, Steve. Yes, 16 bit 44Kbps mono .wav. Same as a music CD, except mono instead of stereo gives you twice as much time.