MP3 / WMA encodes differ from WAV (length)

Karma2001 wrote on 3/15/2002, 9:05 AM

I've noticed when I enocde a WAV as MP3 or WMA that the resulting file is different from the original across the time line. (example: A WAV file of exactly 3 minutes might encode to 3:01 or 2:59).

Does anyone know a way to encode that produces an output file that matches the original WAV exactly across the timeline?

Thanks much for any help or insight,
Karma

Comments

Cheesehole wrote on 3/15/2002, 2:23 PM

check out this thread:
http://www.sonicfoundry.com/forums/ShowMessage.asp?ForumID=4&MessageID=71507

might be related.

Karma2001 wrote on 3/16/2002, 7:40 AM

Thanks much cheesehole... that is exactly the same issue...

"Just did a quick test. I dropped a WAV on the timeline, rendered to mp3 (160kbits) and then dropped the new MP3 back on the timeline. It appears that the mp3 has 27ms of lead time added to it, shifting the whole song forward by 27ms. The actual length of the song is the same, but the mp3 clip is 27ms longer to account for the added time at the beginning. Seems strange. I have no explaination."

Does anyone know if there is a solution?

Thanks
Karma

Chienworks wrote on 3/16/2002, 10:05 AM

Rewrite the MP3 spec?

Or, preferably ... just deal with it.

barleycorn wrote on 3/17/2002, 1:07 PM

Vegas can usually get close to the exact length (15 samples are often missing from the end if the length is not identical) when saving Windows Media files (128 Kbps).

Sound Forge always adds large amounts of silence (sometimes thousands of samples) at the end of Windows Media files so (pace Chienworks) there is clearly more to this than limitations due to the file formats.