Audacity exports at higher bitrate than desired

[TheSneak]

I am using Audacity 2.0.3 (I think. the about box still says 1.3.14 beta even though i've double checked that I downloaded 2.0.3). I downloaded the zip file, not the installer. I am using Windows 7.

I am trying to edit some of the wav files for the game Half-Life. Windows reports these wav files as being at bit rate 88kbps. When I edit the file and export it to wav, window reports the bitrate at 176kbps and the file size is almost doubled. I have set the sample rate to 16 bit PCM, Mono and export as WAV (Microsoft) signed 16 bit PCM.

Is there a trick to exporting with the same bit rate / sample rate / "whatever settings" as the original file?

Thank you

[kozikowski]

Windows reports these wav files as being at bit rate 88kbps.

What else did it say about those files? The bitrate is a combined rating between the sample rate (44100) and the bit depth (16-bit).

Did it actually say it was a WAV file, or are you assuming that? You can force Windows to show you file extensions and take a lot of mystery out of the process.


Hidden File Extensions
-- Start > My Computer > Tools > Folder Options > View > [ ] Hide Extensions for Known File Types (deselect)
-- Apply (to this folder) or Apply to All Folders
-- OK


In general, people speak of compressed or processed sound files in terms of transmission bitrate and uncompressed files by sample rate and bit depth. So the strong assumption is your original file wasn't a WAV.

Koz

[Gale Andrews]

I am using Audacity 2.0.3 (I think. the about box still says 1.3.14 beta even though i've double checked that I downloaded 2.0.3).

.
I suggest you quit 1.3.14 then uninstall it.

I am trying to edit some of the wav files for the game Half-Life. Windows reports these wav files as being at bit rate 88kbps. When I edit the file and export it to wav, window reports the bitrate at 176kbps and the file size is almost doubled. I have set the sample rate to 16 bit PCM, Mono and export as WAV (Microsoft) signed 16 bit PCM.

To get a 176 kbps mono PCM WAV you will be exporting at 11025 Hz sample rate (in the "Project Rate" box bottom left).

To get half that bit rate, you would halve the sample rate or halve the bit depth. 5500 Hz or so would be a very strange sample rate, so I suspect the WAV's you have are actually 8-bit (either PCM or U-Law/A-Law). If you want to export an 8-bit WAV, choose "Other uncompressed files" in the "Export File" dialogue, then click "Options..." then choose your required encoding.


Gale

[DVDdoug]

With uncompressed files, you can easily calculate the bitrate (kilobits per second) if you know the sample rate (samples per second), bit depth (number of bits per sample) and the number of channels..

Bitrate = Sample Rate x Bit Depth x Number of Channels.

For example, the bitrate for a CD (or a WAV file from a CD) is 44.1kHz x 16-bits x 2 channels = 1411.2 kbps.

With compressed files, it also depends on the amount of compression. But if you know the file size and the playing time, you can (approximately) calculate the bitrate by converting bits to bytes (8 bits per byte), and sometimes you need to convert minutes to seconds.

Bitrate in kbps = (File Size in MB x 140)/Playing Time
(Tha's not exact. There is some rounding in the formula, and there is some variable overhead in the file, adding to it's size.)

[TheSneak]

If you want to export an 8-bit WAV, choose "Other uncompressed files" in the "Export File" dialogue, then click "Options..." then choose your required encoding.

It turns out the original files are unsigned 8-bit PCM. Thanks for the instructions. I was able to save using the original file settings by following this instruction.

In order to determine the properties of the original file, I used winamp to look at the file info which tells me:

• Unsigned 8 bit PCM
• 1 Channel(s)
• 11025 Hz

When I open the files in Audacity, the info panel to the left of the waveform says "16-bit PCM." Are the actual file properties able to be seen in Audacity somewhere?

[Gale Andrews]

In order to determine the properties of the original file, I used winamp to look at the file info which tells me:

• Unsigned 8 bit PCM
• 1 Channel(s)
• 11025 Hz

When I open the files in Audacity, the info panel to the left of the waveform says "16-bit PCM." Are the actual file properties able to be seen in Audacity somewhere?

The info panel shows you the sample rate and mono or stereo, but the bit depth is the resolution the file is being imported at, not the bit depth of the file. The resolution imported at is set at "Sample Format" in the Quality Preferences, so you must have this set at 16-bit instead of the default (preferred) 32-bit float.

I'll add your vote for a feature for Audacity to display file properties.


Gale