Exporting file reduced

[GGBPAM]

Win 7 - Audacity 2.1.2 Lame v3 99.3

I need to export the file at half the size, 10mb instead of 20mb, to be able to upload to the web site. I have been doing this successfully for my church sermons for about 5 years with Audacity 1.2.6. Now with the new version 2.1.2 the method I have used does not work. The file exports at the same 20 mb size.

My method is as follows:
Open message file from desktop
Split screen
Remove one track
Make any edits at beginning or end
Export as Mp3

I'm an 80 year old grandma and could use some help please. I've tried various things such as export as Mono etc.

[steve]

The default MP3 settings in Audacity 1.2.6 were "128 kbps Constant".
Audacity 2.1.2 uses higher quality (larger file size) settings by default.
To use the old default settings, select "Constant" and "128 kbps" in the Export dialog screen:
See: http://manual.audacityteam.org/man/file ... ialog.html

[GGBPAM]

Thank you for your reply.
I came down to the church and tried this today, but it didn't work.
The resulting file which was 20mb going in, was still 20mb.
Can I send you screen shots of what it looks like?

[DVDdoug]

File size is directly related to bit rate (kbps = kilobits per second) and playing time. Half the bit rate is half the file size.

If you know there are 8 bits in a byte you can do a little algebra (and a little rounding) to get:
File Size in MB = (Playing time in Minutes x Bit rate in kbps) / 133

...With compressed files where you target a particular bitrate it doesn't matter if it's mono or stereo. With uncompressed files a stereo file is twice the size (and twice the bitrate) of a mono file (assuming the same sample rate and bit-depth).

[steve]

The resulting file which was 20mb going in, was still 20mb.

How long is the recording?

[GGBPAM]

Approximately 30 minutes.
The originals are 20 to 45 mb that usually reduce down to 6 to 12 mb. These are Sermons from church that I upload to our web site. I just did one successfully using Audacity 1.2.6 on my computer at home. (opendoornovato.org Sermons tab)
I have never had any problem before with just removing one track and then exporting as mp3.
I am trying to accomplish this on the computer at church which has Audacity 2.1.2. But it just doesn't reduce the size of the file. There must be an additional step with the new Audacity software that I am unaware of. When I look at the numbers, bit rate etc. they are all the same in the new version.
Thanks for any help you can give.

[steve]

As a rough rule of thumb. 128 kbps works out at about 0.9MB per minute, so that will give a bit under 30MB for a 30 minute track.
64kbps is half the number of bits per second compared to 129kbps, so that will produce a file half the size of a 128kbps MP3. Try setting the MP3 export format to 64kbps Constant. (Constant bit-rate is usually called "CBR").

64kbps for a stereo track will sound pretty poor quality, but not too bad for mono, so you need to retain your "convert to mono" step. In the next version of Audacity there is an option for MP3s to be "forced" into mono regardless of whether the recording is mono or stereo, so that will save you a bit of time when the next Audacity version is released later this year.