Play time of exported WAV file truncated

[heseltine]

Hello,

When I export a 5 hour recording of Radio 3's Through the Night from audacity to WAV only about an hour is stored on the output WAVE file. I have tried (1) export, (2) export selection, (3) setting the start and end time as 0.00.00 - 5.00.00 for each export and export selection, (4) not setting those times, but the result is the same - only an hour is exported. I was successeful only once so I know it can be done. The WAV file size, however, is fairly large - about 4-6 Gbytes.

Any suggestions as to what I am doing wrong? I am using the current betta.

Many thanks,

Mark

[kozikowski]

Windows doesn't do well with very large files. The limit used to be the famous "2 Gig Wall" where the addressing scheme ran out of poop. Who would ever need files bigger than 2G?

But there is a new one about 4Gig or so. It's not the open ended, sky's the limit that everyone thinks it is. Worse, some programs are aware of Windows' filesize tricks and some aren't.

Just to cover the bases, you are using legal filenames, right? Upper and lower case letters, numbers, dash, and underscore. That's the whole list. I don't use spaces, either. Some machines give unstable results with other characters in the name.

Koz

[heseltine]

Thanks, Koz.

Filenames are proper. The strange thing is that it worked once. You would think that successfully creating a 5 gig file which will run in VLC or MS's media player would suggest there is no problem with the programme or o/s. The problem must lie with me. I'll try it again to see if there isn't some option I am missing.

Thanks again.

Mark

[heseltine]

Well, I retried exporting. This time I set the start time to zero, the end time to 7 hours. I used the 'export' tool and selected Wav. It displayed a message to the effect it was exporting the entire audacity project to wav. It took about 20 odd minutes to export.

I didn't check the size of the audacity file. However the final output wav file was 4.6 Gb (as with the last 2 efforts). As with the last 2 efforts when I ran the wav file on VLC it registered about 46 minutes playing time. I checked the audacity project file. It is a 7 hour long production and there is sound from beginning to end.

This is baffling. Clearly the data is exported to the wav file but MS media player and VLC do not read it as containing anything but about 46 minutes of data.

Perhaps Audacity is defective.

Any suggestions would be gratefully received.

Mark

[kozikowski]

<<<final output wav file was 4.6 Gb >>>

That's about correct for a 7 hour stereo show.

Just for form, what are your Audacity Preferences? 44100, 16-bit, Stereo? Not everybody can deal with 32-bit floating.

Koz

[heseltine]

Bog standard, out of the box. So, 44100, stereo, 32 bit float. I ran a benchmark. Don't know if that is of help. The response was:

• Using 63310 chunks of 265 samples each, for a total of 32.0 MB.
  Preparing...
  Performing 100 edits...
  Time to perform 100 edits: 25875 ms
  Doing correctness check...
  Passed correctness check!
  Time to check all data: 15187 ms
  Reading data again...
  Time to check all data (2): 15078 ms
  At 44100 Hz, 16-bits per sample, the estimated number of
  simultaneous tracks that could be played at once: 25.2

I'm going to try to record a smaller batch and see what happens tomorrow.

// edit:

I've read the recording tips on the web. It has this warning:

• Note when exporting your recording that there is a file length limit for WAV and AIFF files. The file size is set in the headers as an unsigned 4 byte integer, which imposes a 4 GB limit, except that some media players interpret the file length as a signed number, which imposes a 2 GB limit.

The successful file was under 4 gigabytes and the failures were over that limit. So, it seems the problem is with the wav file limitations. Perhaps I have no choice but to save in mp3 (which appears to take hours).

// end edit

Thanks

Mark

[waxcylinder]

Perhaps I have no choice but to save in mp3 (which appears to take hours).

Or you could break the WAV files into chunks aof an hour apiece say -use the labelling function to create track labels (CTRL+B k/b shortcut) at each break - and then use Export Multiple to create a set of WAV files.

Note that MP3 is lossy and will throw some audio data away (you probably know that already, I'm guessing) - at a bitrate of 320 you are unlikely to notice the degradation.

WC

[heseltine]

Or you could break the WAV files into chunks aof an hour apiece say -use the labelling function to create track labels (CTRL+B k/b shortcut) at each break - and then use Export Multiple to create a set of WAV files.

Note that MP3 is lossy and will throw some audio data away (you probably know that already, I'm guessing) - at a bitrate of 320 you are unlikely to notice the degradation.

WC

Hello, WCyl,

Thanks. I agree. I'd like not to use MP3 not least because the compression takes forever, and I want to play back selections of Radio 3 at work (though my speakers are not the best so it might be a moot point).

I was able to break the file into two parts by exporting selections of approx 240 mins each. However, what does the labelling function do? I've looked up 'label' in the Audacity site. I understand (I think) the idea of setting a label at a defined point. Does it act as a marker? And then how would you export, say, a 2 label piece (eg 6 hours of Radio 3)? Is labelling simpler than exporting a selection of minutes twice (e.g., by setting times thus - 00:00:00 to 03:50:00; and 3:50:00 to 5:30:00)?

I'll experiment a bit over the weekend. But a practical tip or two would be appreciated.

Cheers,

Mark

[kozikowski]

<<<Bog standard, out of the box. So, 44100, stereo, 32 bit float.>>>

That's standard for Audacity, but that's not a standard WAV file. 32-bit floating sometimes gets stuck in certain players and processors. Change to 16-bit and see if that doesn't work out better.

http://audacityteam.org/forum/viewtopic ... 11&t=10190

Koz

[heseltine]

Thanks Koz.

I've switched to 16 bit but I believe it remains restricted to approx. a 4 gb file size in wav. I've therefore resorted to breaking up the recording into two pieces. I'm still working out the relationship between GB and minutes using 16 v. 32 bit. Seems, I think, that recording at 16 bit cuts the size in half. So, I should be able to get about 8 hours into 4 gb, but this is still a work in progress.