How to re-encode an MP3 file for Camtasia 8.6 (or for a legacy MP3 editing tool).

Command:

ffmpeg -i input.mp3 -codec:a libmp3lame -b:a 192k -write_xing 0 -id3v2_version 0 output.mp3

Details:

Camtasia 8.6 misunderstands VBR: Variable bit rate MP3 files. So Camtasia 8.6 shows the wrong MP3 audio length. To avoid this Camtasia 8.6 issue, use CBR: constant bit rate and invalidate new headers. (Or use a WAV file)

Options:

• -b:a 192k: Constant bit rate to 192kbps
• -write_xing 0: No Xing header. The Xing header records the timing information for the variable bit rate MP3 file. But when I use CBR, this is not needed. Camtasia 8.6 seems to have failed to recognize Xing VBR MP3 files.
• -id3v2_version 0: Use id3v2 version 0 tag. Camtasia seems to have failed to recognize the ID3v2 header > 0 tag. This loses the metadata.

To see the MP3 encoding info:

• ffmpeg -i input.mp3
• mediainfo input.mp3