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Topic: What causes MP3's to have synch errors (Read 4990 times) previous topic - next topic
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What causes MP3's to have synch errors

Hi Guys

I have been going through my Mp3 collection with Foobar and Mp3utitly.

I am finding quite a few files have synch errors.

Yet in some folders my Mp3's have no errors reported !

What causes these synch errors ?

Most of my file shave been downloaded over the years. What did the original rippers of the files do wrong to cause this ?

Was it some bad settings they chose, or perhaps the early CD burners ?

Are there more or less of these files out there now ?

Regards

Digby

What causes MP3's to have synch errors

Reply #1 –
Sync error means data corruption, or missing frame(s) (headers). Namely, it means your MP3s are corrupted, however slight.

What causes MP3's to have synch errors

Reply #2 –
Quote
Sync error means data corruption, or missing frame(s) (headers). Namely, it means your MP3s are corrupted, however slight.
Could anyone elaborate on this, and perhaps address some of the questions in the original post ? Thanks.

Regards,
Madrigal

What causes MP3's to have synch errors

Reply #3 –
Sync error means that at a place where a frame header should be (that is immediately after the previous frame) none is found by the decoder.

In most cases the cause are missing bytes in the frame immediately before the error, so that the next header or a part of it is part of the flawed frame. This byte shift either lets the decoder skip or mute this frame, or an audible error (blip or so) occurs.

After this frame there is no frame header, and the decoder has to seek for the next bit pattern that looks like a valid header. Actually it should look for 3 valid headers & frames in sequence before being sure the resynchronization was successfull.

When downloading files there may be transmission errors, therefore it is not a bad idea to zip MP3s even if this has no benefit sizewise. But errors will be detected when unpacking the zip. Also interrupted and resumed transfers sometimes show errors, or at least until several years ago I noticed this. Nowadays the resume algorithms seem to be good.

Regards
Sunhillow

What causes MP3's to have synch errors

Reply #4 –
Segmented downloading can also cause errors like this, even with modern downloaders. Sometimes the resume algorithms aren't that great, and still causes data corruption.
If your files were fine when you downloaded them, it may've been caused by bad sectors on your drive.
It also depends on where you obtained them in the first place, some P2P networks don't have the best hashing methods and errors can slip by. You may've also gotten a copy of a file that was corrupted but somehow became popular on the network.

And yes, it is a good idea to zip/rar/etc the files, so you can at least be sure that the files are coming through intact (though it won't save you from the source files already being damaged).

In any case, all you can really do is re-rip the tracks and re-encode, or download the MP3s again from wherever you got them.

What causes MP3's to have synch errors

Reply #5 –
I have some tracks which foobar2000 says have sync errors; but EncSpot analysis says they have no sync errors. Are one of these apps unreliable regarding error detection, or is there another explanation?

What causes MP3's to have synch errors

Reply #6 –
Well, in all honesty I'd be more likely to trust foobar2000, especially since everytime I've seen it in foobar2000 there's an audible glitch in the sound.
You can always try to use mp3trim and see if the results agree with foobar2000, it seems to report missing/corrupted FHs too. (normal version limits you to 7MB files though)

What causes MP3's to have synch errors

Reply #7 –
Quote
Well, in all honesty I'd be more likely to trust foobar2000, especially since everytime I've seen it in foobar2000 there's an audible glitch in the sound.
You can always try to use mp3trim and see if the results agree with foobar2000, it seems to report missing/corrupted FHs too. (normal version limits you to 7MB files though)
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Great guys,

Keep it coming !

Looks like an interesting topic

Regards

Digby

What causes MP3's to have synch errors

Reply #8 –
It seems you all think that these synch errors are caused by errors caused when downloading. 

I wonder if this is the cause as most file formats have some sort of checksum proceedure.

Could they also be caused by some of the early style CD burners that did not have good  buffer overload techniques ?

regards

Digby
NZ

What causes MP3's to have synch errors

Reply #9 –
Quote
Could they also be caused by some of the early style CD burners that did not have good  buffer overload techniques ?
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You probably mean buffer underrun when talking about cd burners and what that caused was a coaster, not a corrupted file. A sync error simply denotes there's some corruption in the file which can obviously happen whenever the file is manipulated. Having said that the weakest link usually is network transfer, so that's probably where most corruption took/takes place, although a file can also get corrupted just by sitting on a harddrive when that starts failing or it develops file system problems.