Noise at the beginning of tracks

[mattp]

Hi, newbie to the forums here, I've been using rockbox for ages on my Video iPod 5G 30GB but I've recently had a problem with v3.0 and the daily build (today) where on certain albums only, there is a strange noise at the beginning of the track and the track length is displayed incorrectly, it shows as being longer. Only a few albums have this problem, most are fine. The problem albums play fine on my PC in WMP11.

Anyone had this problem before?

Cheers

Matt

[Chronon]

It would be helpful to know some characteristics of the files.  What codec, bitrate, sampling frequency, etc.?  Are these common to the problematic files or not?

[soap]

What codec are the problematic files?
What bitrate?
What sample rate?
What type of tags?
Do these exact files play properly in WMP11?  (as in  playing them off your iPod when it is plugged in while in disk mode.)

[mattp]

All files are mp3 with different bitrate, some are 192, some 256 some 320kbps
not sure of the sample rate, what's a quick way to find out?
ID3v2.3

One of the files just came up on the rockboxed ipod as being 40kbps and mp2 using the UniCatcher theme which is wrong. The files play fine and the details show as correct when played in WMP11 in disk mode.

Cheers

[spike66]

I had exactly the same "problem" with 3.0 and recent builds on some mp3 files, and found out that those files had junk data at the beginning, and the length header was wrong as well. So the problem was on the files, not Rockbox, although WMP and other players "overlooked" that problem, as previous Rockbox builds also did... it is as if the recent builds were "more picky" than earlier ones. I tried fixing the files but after (not much) trying and not succeeding, I decided to rip the tracks again. Now, at some point I thought maybe Rockbox should play the problematic files as well, but now I think it's actually a good thing that it "detects" corrupted tracks.

[soap]

Mr. Kitt brings up the next question I was going to ask:
How much "stuff" is in your ID3v2.3 tags?
Do you have large embedded album art in that tag at the start of the file?
Do you have other binary blobs stuck in there? 

If you're keen on v2.3 tags, perhaps set up Foobar2000's preferences for MP3 tagging to use "compatibility mode" (so you don't write 2.4 tags)  and force a simple rewrite of the tags of the problematic files (or a copy of them) to see if this fixes the issue.

_{EDIT:  Removed extra parentheses.}


EDIT #2:
Though that being said, the fact the WPS reported (supposedly incorrectly) 40kbps makes me wonder if the LAME (assuming) header is wrong?  To the best of my knowledge WMP ignores the LAME header.
Can you as well do the math to verify 40 is a wrong number?  (harder to do if you have large embedded album art)

[mattp]

There isn't much stored in my tags, just the usual artist, album, track number etc. No pictures or comments. I don't know why i have used v2.3 tags, i've just used WMP11 to find the info. I've done some quick inaccurate maths and it seems the 40kbps is right for what rockbox displays the track length as being. The track is 7.82Mb and 5.00mins long which should bring out a figure around 213kbps which is what WMP says. Rockbox displays the track length as 27.19mins so it comes out around 40kbps.

I will try and rip the problem albums again soon, buti'm away from my cd collection at the moment so it won't be for a couple of weeks. I might try a pre 3.0 version of rockbox before to see if the problem remains.

Thanks for your help

[spike66]

There isn't much stored in my tags, just the usual artist, album, track number etc. No pictures or comments. I don't know why i have used v2.3 tags, i've just used WMP11 to find the info. I've done some quick inaccurate maths and it seems the 40kbps is right for what rockbox displays the track length as being. The track is 7.82Mb and 5.00mins long which should bring out a figure around 213kbps which is what WMP says. Rockbox displays the track length as 27.19mins so it comes out around 40kbps.

If you are interested, you might want to use a checking tool like this http://www.download.com/MP3-Checker/3000-2141_4-10543407.html?tag=mncol&cdlPid=10543408

There's also a plugin included with Rockbox for fixing the length (Xing heather), VBRFix http://www.rockbox.org/twiki/bin/view/Main/VBRfix?topic=PluginVBRFix. In my case, it corrected the lengths, but the noise didn't disappear.

[mattp]

Thanks, i've tried MP3 checker and the files came out as bad, as expected. I then used a program i found called MP3 repair which allowed me to remove the noise at the beginning, this also reduced the time displayed by rockbox slightly but not to what it should be, that plugin had no effect either. I've only tried one file so far so will try others and see what happens.

[saratoga]

If the files are corrupted, I wouldn't bother trying to repair them and would just get fresh ones from CD or wherever.