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Unification of audio collection - convert or not to convert, that is t
Remuss
post Dec 29 2013, 17:32
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Hello to all audio experts here.

I have a question which is far beyond my general knowledge of audio conversion so I would like to hear you opinions.

My problem is relatively simple. I have 10 710 mp3 files, all of them are speech / voice education genre. I would like to unify sample rate, bitrate and channels profile to let say 2 groups (CBR) or 1 group (VRB) according to the source parameters (see below). For example:

Joint stereo, 48 and 92 MP3 CBR, 32000 Hz or 44100 Hz
or
Joint stereo, VBR 8 or 7, 32000 Hz

Reducing the file size is not a priority. Rather repack and unify current quality :-)

I know that mp3 to mp3 transcoding could cause some loss in quality (probably not very important for speech) but still another question is whether I should do this at all.

If you know some guide or software which could help me, please share you knowledge.

Thank you !


According to foobar2000, here are some general numbers:

Sample rate:
44100 Hz (51.3%); 22050 Hz (30.7%); 32000 Hz (6.4%); 48000 Hz (4.2%); 16000 Hz (3.3%); 11025 Hz (3.1%); 24000 Hz (1.1%)

Bitrate range:
16 kbps - 192 MP3 CBR
MP3 VBR 3-9

Channels (Stereo/ Mono):
2 (57.5%); 1 (42.5%)

Codec profile:
MP3 CBR (80.1%); MP3 VBR V4 (4.8%); MP3 VBR V6 (4.7%); MP3 VBR V3 (3.3%); MP3 VBR V5 (3.1%); MP3 VBR (1.3%); MP3 VBR V2 (1.2%); MP3 VBR V0 (0.8%); MP3 ABR (0.5%); MP3 VBR V8 (0.2%); MP3 VBR V9 (0.0%)

Tool:
LAME3.99r (11.2%); LAME3.98 (4.0%); LAME3.97 (3.1%); LAME3.98r (1.7%); LAME3.96r (1.1%); ST (1.1%); iTunes v4.8 (0.8%); LAME3.93 (0.7%); LAME3.92 (0.6%); iTunes v4.2 (0.5%); LAME3.96 (0.4%); LAME3.90 (0.3%); LAME3.95 (0.0%)

Tag type:
id3v2.3|id3v1 (72.9%); id3v2.3 (7.8%); id3v2.2 (4.0%); id3v2.4 (2.1%); id3v1 (1.9%); id3v2.3|apev2|id3v1 (1.3%); id3v2.4|id3v1 (1.0%); apev2|id3v1 (0.4%)
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markanini
post Dec 29 2013, 17:50
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Why?
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Remuss
post Dec 29 2013, 18:08
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QUOTE (markanini @ Dec 29 2013, 17:50) *
Why?

Why what? Why to do such conversion? To standardize size and other parameters while keeping good quality. Reducing size is not a priority but if I spent some GB it would be nice.
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markanini
post Dec 29 2013, 18:40
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Keep in mind that there's no quality to gain by upconverting, and in the case of mp3 there's certainly a chance of quality reduction when transcoding.
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garym
post Dec 29 2013, 19:10
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The only thing I see worth standardizing is your tagging. I suggest you covert all to a single tag type. I find that ID3V2.3 to be the most used by various players for mp3. Mp3tag or foobar2000 are good tools for this.
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Glenn Gundlach
post Dec 29 2013, 21:57
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Well if it's space, forget that. 3T drives go on sale for $100. I expect all your files would only make a dent in the space available. 'Unify the quality' implies reducing to the lowest value. Again, why? The typical answer used to be to conserve space but that is no longer an issue.

GaryM suggested standardizing on the tagging which seems a very good idea to me. Having something you can't find is the same as not having it. Get creative with the folder structure as that can speed up finding info too.

Happy New Year



This post has been edited by Glenn Gundlach: Dec 29 2013, 21:59
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Remuss
post Dec 30 2013, 08:09
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Thank you for useful information. Standardizing of tags seems interesting I will do that.

What about 'simple' conversion mono to joint stereo? Do this worse quality too?


This post has been edited by Remuss: Dec 30 2013, 08:46
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A_Man_Eating_Duc...
post Dec 30 2013, 09:26
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Yes quality will worse.

Forget about the different bitrates and just work on your tags and folder structures.


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includemeout
post Dec 30 2013, 09:36
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Again: the zero benefit wouldn't justify the hassle and you might as well end up with files sounding worse than the original ones.

There is no need for this standartization you're after: For your player for instance, these files are only 'horses for courses' and it doesn't make any difference whatsoever.

The bottom line: transcoding from LQ lossy to lossy is, unless extremely necessary, to be avoided as the plague.


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Porcus
post Dec 30 2013, 09:49
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I do agree with others, why try to "unify" all this?


Arguments against:

- Unless you go CBR, all files will have different bitrates anyway.

- If space is no issue -- and it would likely not be for your archive, though maybe for a portable player or a phone -- then repacking by mp3packer (that is lossless!) is not necessary.

- Why care about joint or true stereo?

- So you have different LAME versions displayed. Why care? Your iTunes 4.2 files will forever have gone through iTunes 4.2 even if it does not show if you transcode it through a second processor. (I should add, for the purpose of getting rid of too many "FLAC" entries to scroll past to see if there are mp3's in a selection of multiple items, I did once get rid of all my FLAC 1.1.*'s -- but that is entirely lossless.)

- That "inaccurate" reported length thing: usually a header misstating the actual number of frames. Decoders read through this just fine, usually -- and if not, the error might get permanent if you transcode. It seems to me that you can even lose gapless playback by reencoding.
(This is the reason why foo_bitcompare always reads through the files even if different lengths -- it does not conclude that the files do indeed differ in length until it has actually decoded it and counted.)



What you might possibly care about -- mainly related to compatibility:

- Sampling frequency. You could sometimes get into compatibility issues. I have a DAC that refuses some sampling rates, but I solve that in foobar2000 by foo_dsp_resampler_mod2 ; 11025 and 22050 are resampled on-the-fly upon playback to 44100, while 16000 and 32000 are resampled to 48000.

- VBR/CBR: at worst you may encounter an old obsolete mp3 player which insists on CBR. If not, then do not care. If you do, then mp3packer can losslessly repack a VBR to a CBR (repacking broken files might not be lossless though! "There is no standard way to decode a nonstandard file").

- Size you said? Not for your archive, but maybe for a portable player? mp3packer is your friend again. Use the WinMP3packer frontend. I sometimes repack my new mp3s out of curiosity: what is there really in those 320 CBR files the labels ship around in their samplers? I once got a 320 down to < 192. A "wow!" case.

- Tags yes.

This post has been edited by Porcus: Dec 30 2013, 09:53


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Aleron Ives
post Dec 31 2013, 02:48
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QUOTE (Porcus @ Dec 30 2013, 00:49) *
Why care about joint or true stereo?

To be clear, this seems to imply that joint stereo is somehow "less stereo-ish" than simple stereo, which is not the case. Converting between LR stereo and MS stereo is a lossless procedure that has no impact on the stereo separation, which is why even lossless codecs take advantage of the bitrate savings made possible by joint stereo. I doubt you were trying to suggest such a thing by saying "true" stereo, but it bears clarification, lest Remuss misunderstand your point.
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zipr
post Dec 31 2013, 04:01
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Depending on how you listen to these, what you're playing them back with, and if there is much variety in the volume of the sources, adding Replaygain info or using MP3Gain to normalize the volumes of the files may make for a more pleasant overall listening experience.

This post has been edited by zipr: Dec 31 2013, 04:02
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Remuss
post Jan 5 2014, 19:55
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Thank you again you all for helpful and useful information.
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2Bdecided
post Jan 6 2014, 10:48
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QUOTE (Remuss @ Dec 29 2013, 16:32) *
another question is whether I should do this at all.
No.

However, you might choose to upconvert any ones which cause incompatibility issues. e.g. some players don't like mono files, some players don't like very low sample rate files (don't like = won't play at all or will play very badly). If you're using player(s) which are happy with all these files, there's no point transcoding them.

Cheers,
David.
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includemeout
post Jan 6 2014, 11:22
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Hopefully the message has finally come across now:

It is NOT worth it and it does NOT improve anything!


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