Adding a padding byte to MP3 frames

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Adding a padding byte to MP3 frames

Christopher Nice
Short version: Is the padding byte that gets added to some MP3 frames actually padding (e.g. not important to playback), or is it audio data? Can a padding byte be added to the correct frames of a file not originally containing them?

Here's the long version:

My company has a large number of audio files we are trying to play in the browser. We have found that some browsers do not seek to the correct location, and the seek error is larger the farther the browser seeks into the file. I found that re-encoding the file using the same bitrate, sample frequency and so on using LAME fixes the seek issue.

I have determined that this issue is caused because the MP3 encoder our company is using does not add the padding byte at all, whereas LAME adds it to the correct frames. I'm hoping to correct our files without re-encoding by adding the padding bytes. I made one attempt to fix our files by setting the padding bit in the header and adding a byte to the end of the correct MP3 frames, but this garbles the file. Is there more to it than that? Is what I'm trying to do even possible?

Thanks for your time,
Christopher

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Re: Adding a padding byte to MP3 frames

Robert Hegemann
Hello Christopher,

to correct padding issues, I recommend you to use the mp3packer tool.

http://wiki.hydrogenaudio.org/index.php?title=MP3packer

Ciao Robert

Am 05.09.2013, 19:01 Uhr, schrieb Christopher Nice  
<[hidden email]>:

> Short version: Is the padding byte that gets added to some MP3 frames  
> actually padding (e.g. not important to playback), or is it audio data?  
> Can a padding byte be added to the correct frames of a file not  
> originally containing them?
>
> Here's the long version:
>
> My company has a large number of audio files we are trying to play in  
> the browser. We have found that some browsers do not seek to the correct  
> location, and the seek error is larger the farther the browser seeks  
> into the file. I found that re-encoding the file using the same bitrate,  
> sample frequency and so on using LAME fixes the seek issue.
>
> I have determined that this issue is caused because the MP3 encoder our  
> company is using does not add the padding byte at all, whereas LAME adds  
> it to the correct frames. I'm hoping to correct our files without  
> re-encoding by adding the padding bytes. I made one attempt to fix our  
> files by setting the padding bit in the header and adding a byte to the  
> end of the correct MP3 frames, but this garbles the file. Is there more  
> to it than that? Is what I'm trying to do even possible?
>
> Thanks for your time,
> Christopher

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