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Topic: OFFSET (in encoded mp3, m4a) !? (Read 5250 times) previous topic - next topic
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OFFSET (in encoded mp3, m4a) !?

Situation (in step by step):

1. have original kick.wav
2. encode to mp3 or m4a
3. open in audacity, audition
4. size of encoded file is incrased on prepended offset

Question: WTF ?

OFFSET (in encoded mp3, m4a) !?

Reply #1 –
Lossy encoded files contain blocks of data or "frames" of fixed size. The size is different for different codecs, but the result is that every file of that type contains audio data that is a multiple of the frame size.

In addition, since the data for these frames overlaps the adjacent frames, the first and last frame extend beyond the original data, so there is a time shift, or offset, between the original and the encoded.

Some encoders add information in a tag that specifies both the offset and the original size of the file so that it is possible to correct for both of these effects.

OFFSET (in encoded mp3, m4a) !?

Reply #2 –
Quote from: pdq on
Lossy encoded files contain blocks of data or "frames" of fixed size. The size is different for different codecs, but the result is that every file of that type contains audio data that is a multiple of the frame size.

In addition, since the data for these frames overlaps the adjacent frames, the first and last frame extend beyond the original data, so there is a time shift, or offset, between the original and the encoded.

Some encoders add information in a tag that specifies both the offset and the original size of the file so that it is possible to correct for both of these effects.

I guess it's not possible to disable this time-shifts and offsets.
Ok. I got answer.
thnx.

OFFSET (in encoded mp3, m4a) !?

Reply #3 –
If you decode the mp3 to wav using a decoder that accounts for these parameters in the tag then you should get the same length with the offset removed. Then load the wav file into your editor.

BTW, what are you trying to accomplish? Are you trying to compare the original wav to the mp3?

OFFSET (in encoded mp3, m4a) !?

Reply #4 –
Quote from: pdq on
If you decode the mp3 to wav using a decoder that accounts for these parameters in the tag then you should get the same length with the offset removed. Then load the wav file into your editor.

BTW, what are you trying to accomplish? Are you trying to compare the original wav to the mp3?

Accidentally open encoded in mp3 wav file in audition and i'm shocked, what time-shit doing here.
Now, thanks to you i get it, for playing it's ok, but for editor better decode to wav and then open.
Strange that no one don't solve the problem with this offsets when open directly encoded file in audio editor. When i will save after editing offset wiil be saved: it's NO good.
From this moment, only wav (maybe i should try raw ? hmm...) !
thnx man.