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Topic: Transcoding with lame - missing samples? (Read 2892 times) previous topic - next topic
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Transcoding with lame - missing samples?

Hi all.
I have some high bitrate lame encoded mp3's, and would like to convert them to a lower bitrate for a flash player.  However, I'm confused as to why lame adds/deletes samples upon recoding.

For example, a 320kbs cbr file was rencoded using the same settings. After decoding both files to wave - again with lame - the EAC compare tool showed the first file was missing 1105 samples from the beginning compared to the second file. If I've read the results correctly that means the second file had been padded at the front. Why does this happen? I thought lame wrote info about encoding delays etc into the files. Is it just not using them?

This is no big deal for me. But I'm curious as to how and why this happens.

Transcoding with lame - missing samples?

Reply #1 –
LAME decoder isn't perfect (more info in this post), decode/reencode with for example foobar2000 to avoid such problems.

Transcoding with lame - missing samples?

Reply #2 –
Shortly after the issue was brought up (again) in that post, a lame.exe was released that fixed the decoding issue. You can get it at RareWares.

Transcoding with lame - missing samples?

Reply #3 –
Quote
Shortly after the issue was brought up (again) in that post, a lame.exe was released that fixed the decoding issue. You can get it at RareWares.
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Well ain't I a drongo. Saw that version and just overlooked it. I'll give it a try.

So this is just a decoding problem, nothing to do with encoding? I read that foobar2000 gave proper results but couldn't work out how since it relies on lame to encode mp3's.
Does that mean if I go from mp3 --> mp3, fb2k uses it's built in decoding routine as the intermediate step, rather than lame's?

Transcoding with lame - missing samples?

Reply #4 –
Yes, LAME as an encoder is all fine, but as decoder it tended to be buggy. Foobar2000 as a player has its own decoding routines for MP3 (one of the finest), it uses external encoders for encoding only, so when you reencode with fb2k the file is decoded by fb2k and then encoded by external encoder (LAME in this case).
 

Transcoding with lame - missing samples?

Reply #5 –
I meant to say in my last post that I hadn't used fb2k much. It overwhelmed me with all the options etc. But after playing with it for a few hours, I love it. Definately the best way to do what I asked about. And it writes the tags to the new files! Great stuff.

And thanks for the help, all.