The MP3 target is fixed at 192 kbps
PrivateMP3 does not present 128, 256 or 320 kbps buttons. Every MP3 output is requested from the encoder at 192,000 bits per second. The number describes the target data rate of the new MP3 stream; it does not describe the bitrate, sample rate or quality of the source track.
Cuts affect how many seconds are encoded, not the target bitrate. Changing from MP3 to M4A or WAV changes the output method, while selecting a different audio track changes the source being processed.
Calculate the data portion from duration
The estimate beside Convert uses target bitrate divided by eight, multiplied by the kept duration. Using decimal megabytes, the calculation is:
size in MB = bitrate in kbps × seconds ÷ 8 ÷ 1000
| Reference bitrate | Per minute | Per hour |
|---|---|---|
| 128 kbps | 0.96 MB | 57.6 MB |
| 192 kbps used here | 1.44 MB | 86.4 MB |
| 256 kbps | 1.92 MB | 115.2 MB |
| 320 kbps | 2.40 MB | 144.0 MB |
The other rows are reference calculations, not controls available on PrivateMP3. Headers and encoder details can make the saved file differ slightly from the arithmetic, which is why the interface labels its number About rather than promising an exact byte count.
At the same total bitrate, mono does not automatically halve these figures. A mono file becomes smaller only if it is encoded at a lower total bitrate. PrivateMP3 keeps the selected track's channel count and offers no mono switch.
Bitrate cannot repair the source
A higher output bitrate cannot restore clipped peaks, remove room noise or reconstruct detail discarded by an earlier lossy encode. If a video contains AAC, converting that track to MP3 first decodes the AAC and then performs another lossy encoding. If the input is already MP3, cutting and exporting MP3 creates another MP3 generation.
There is no universal bitrate at which speech or music becomes indistinguishable. The result depends on the source, encoder, audio material, listening equipment and listener. Claims that 128 kbps is always transparent, or that nobody can hear a difference above 192 kbps, are not reliable operating rules.
Choose the processing route before comparing numbers
- Use MP3 when the receiving application requires MP3 or its documented support is the safest choice. PrivateMP3 will write 192 kbps.
- Use M4A packet copy when the selected source is AAC, the complete timeline is unchanged and the receiving application accepts M4A. The original AAC packets are then kept instead of making a new MP3.
- Use WAV when a downstream editor or analysis program wants 16-bit PCM. WAV avoids another lossy encode but is much larger and cannot improve an already lossy source.
The practical decision is therefore not “which unsupported bitrate button should I choose?” It is whether the next application needs MP3, can accept the existing AAC in M4A, or needs PCM for editing.