Audacity keeps adding silence at the beginning of my exports

Special Interest Groups Audio Processing
1

Audacity,

I have a huge problem… I am converting (and cutting) over 2,000 audio files. And I need them precisely trimmed, with NO silence at the beginning of the track and no silence at the end.
The problem is that when I cut/trim the file perfectly in audacity, and then export the file… it seems fine, but when I open the fiile back up in Audacity (or any other audio app), there is silence (a leader) at the beginning of my file…!!! Why does audacity not export the EXACT trim? It keeps adding back some silence at the beginning. :frowning:

Please see screengrab here:
http://www.packagefromsanta.com/AudacityScreengrab.jpg

PLease help, i have a huge deadline looming and need to get this resolved.

(I am exporting to 16bit, 8khz, Mono, MP3)

Thank you in advance,
DJ

2

The problem is not Audacity. The problem is the MP3 format specification.
MP3 does not support exact start / end positions. There is always al little bit of leading silence at the start of the MP3.

Wikipedia describes the issue (http://en.wikipedia.org/wiki/MP3#Design_limitations)
“Encoder/decoder overall delay is not defined, which means there is no official provision for gapless playback.”

If you need an exact start, you will need to use a different file format, for example WAV or OGG.

3

Ughhh… thank you very much for your reply.

I will need to find a work around.

Thx
DJ

4

Super frustrating when editing audio that needs to match a video. As a workaround, after I export, I import the new mp3 so it shows up as a second track (still in Audacity). I zoom in and highlight how much silence got added, then open the mp3 in an old version of WavePad (1.0), zoom in and highlight that same amount, delete, and save.

5

You are replying to an ancient topic (10 years old).

The LAME encoder can now add a bit of metadata to the MP3 to tell the decoder how much padding has been added. MP3 decoders that support this feature are then able to automatically remove the padding so that the start time and length are exactly correct. The special tag is called “–nogap” because it allows albums that are split into multiple MP3 files to be played in sequence without gaps between the files

Audacity supported this feature for many years, but unfortunately it is now broken: https://github.com/audacity/audacity/issues/3778

6

As handy as it is, MP3 has some serious problems built-in. Because of the erratic start and stop times, you can’t make an MP3 loop, either. The beginnings and ends are never going to reliably line up.

MP3 gets its small, convenient files by re-arranging sound and musical tones and throwing some of them out. If you make an MP3 from an MP3, it throws out even more tones. Never do production in MP3.

MP3’s full family name is MPEG-1, Layer 3. It’s part of a video format. It was always intended to depend on its associated video channel for sync.

Still, not bad for an audio format cranking along since 1993.

Koz