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Loud "pop" when changing MP3 tracks
soviet123
post Oct 7 2011, 03:26
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Hello all,

New guy here.

Recently I've discovered that on specific tracks, when the song is changing, there would be a loud "pop". The problem exhibits when one track has finished playing and the next track is automatically loaded. This does not happen if I change the tracks manually by pressing the FF key. For example, the Track 3 would have finished playing, and the moment Track 4 is loaded, a loud "pop" is transmitted through my earphones.

I have checked the files (Track 3 and 4 in my example) both with Audacity on Linux and MP3DirectCut on Windows XP. There are no frequency spikes which would indeed indicate that the "pop" is somewhere "between" the two tracks.

The solution is actually very simple: Using MP3DirectCut, I remove a tiny bit of audio (less than one second) at the end of the preceding track (Track 3 in my example). Just like that, no more loud "pop" sound.

Now. It is important to note that as of now, this problem exists only on my portable MP3 player. The same tracks, tested either on RhythmBox (Linux) or foobar2000 (Windows XP), do not have that "pop" in between.

I believe that it is of equal, if not more, importance that the tracks have been gained down using MP3Gain. The original volume would be at around 98dB and they have all been gained to around 89dB (MP3Gain default).

The tracks were ripped from legit Canadian HMV CDs using dBpoweramp CD Ripper to FLAC. The FLAC is then converted to MP3, also using dBpoweramp. Lastly, MP3Gain is applied, and the tracks transferred to my MP3 player.

I have a total of 688 tracks, all processed with the above procedure. To date, I only find 2 cases of "pop". One of them has a pop only in the right channel while the other has a much louder pop in both channels.

...Which basically leads me to two questions:
1) Does my MP3 player have a decoding fault?
2) Is the usage of MP3Gain causing this?

Thank you all very much!
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Juha
post Oct 7 2011, 04:26
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This is common issue when you record vinyl/cassette and then cut the recording into pieces. If you don't add fade in/out into cutted audio data you'll probably get pops because of the remaining gain is dropped down to zero (or rised up to something) too fast. IIRC, DC offset may produce pops as well.

You can find the culprit by checking the audio data after every processing step you do (just zoom the ends of the datat in some audio editor close enough).

Juha

This post has been edited by Juha: Oct 7 2011, 05:08
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db1989
post Oct 7 2011, 11:13
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QUOTE (Juha @ Oct 7 2011, 04:26) *
This is common issue when you record vinyl/cassette and then cut the recording into pieces
Meet:
QUOTE (soviet123 @ Oct 7 2011, 03:26) *
The tracks were ripped from legit Canadian HMV CDs using dBpoweramp CD Ripper to FLAC. The FLAC is then converted to MP3, also using dBpoweramp. Lastly, MP3Gain is applied, and the tracks transferred to my MP3 player.

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Nick.C
post Oct 7 2011, 12:14
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Could this be a tagging issue?

As a test, remove tags from two tracks (that have previously exhibited the popping behaviour on automatic change) and then play them - if there's no pop then there's a tagging problem.


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Juha
post Oct 7 2011, 15:30
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QUOTE (db1989 @ Oct 7 2011, 13:13) *
...



Topic?


I knew it's CD in question ... just wanted to give some ground info for the next clause in my reply.

Juha
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soviet123
post Oct 7 2011, 23:58
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QUOTE (Nick.C @ Oct 7 2011, 07:14) *
Could this be a tagging issue?

As a test, remove tags from two tracks (that have previously exhibited the popping behaviour on automatic change) and then play them - if there's no pop then there's a tagging problem.

...You know what, you might be onto something.

I do remember that after I remove that tiny but of audio, my MP3 player would recognize that track as "Unknown". I put that track back on my computer, yet all the tags are present and are correct. I had to delete and re-tag that track for the player to properly recognize it again.
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slks
post Oct 12 2011, 09:41
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That was the first thing that popped into my mind, that there's tagging or some other sort of metadata at the end of the files causing this issue. Perhaps foobar and RhythmBox are able to see that these tags (if that is what is causing it) are not MP3 data and disregard them, while your other player tries to decode the tags into audio and gives you that nasty pop?

I'm thinking there might be APEv2 tags that ended up in the files, or perhaps ID3 tags written in a way that's incompatible with your player, or something else unknown that got added on there somehow. I don't think it'd be possible to figure out exactly what it is, without examining the files themselves, but that's beyond my skill.

MP3DirectCut surely re-writes the MPEG stream when it does its editing, and seems to remove tags, based on what you say. So it makes sense for the pop to disappear in the "cut" files. Perhaps you could try right click -> Utilities -> Rebuild MP3 Stream in Foobar on the problematic files, and see if that will fix the pop?


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soviet123
post Oct 13 2011, 01:47
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QUOTE (slks @ Oct 12 2011, 04:41) *
I'm thinking there might be APEv2 tags that ended up in the files, or perhaps ID3 tags written in a way that's incompatible with your player, or something else unknown that got added on there somehow. I don't think it'd be possible to figure out exactly what it is, without examining the files themselves, but that's beyond my skill.

MP3DirectCut surely re-writes the MPEG stream when it does its editing, and seems to remove tags, based on what you say. So it makes sense for the pop to disappear in the "cut" files. Perhaps you could try right click -> Utilities -> Rebuild MP3 Stream in Foobar on the problematic files, and see if that will fix the pop?


OK I just found out that "some" of my tracks do indeed have APEv2 tags in them for some reason. They contain three tags, really: APEv2, ID3v2.3 and ID3v1.1.
Only one of them pops, though.

Also I thought MP3DirectCut doesn't decode and re-encode the file...?

This post has been edited by soviet123: Oct 13 2011, 01:48
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