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What Quality are itunes MP4 Audio ?
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30th December 2011
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What Quality are itunes MP4 Audio ?

My dad has a bunch of MP4 songs from itunes and wants to convert them to play on other devices . What audio quality is an MP4 ? Should he just convert them to MP3's ? Are MP4's better quality than an MP3 ?
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My dad has a bunch of MP4 songs from itunes and wants to convert them to play on other devices . What audio quality is an MP4 ? Should he just convert them to MP3's ? Are MP4's better quality than an MP3 ?
MP4 is a container file format that can hold video and audio in a variety of bitrate qualities.

MPEG-4 Part 14 - Wikipedia, the free encyclopedia

AIUI, the MP4 files that iTunes sells are all 256 kbps, and use the AAC (Advanced Audio Codec) which is an arguable advance on the lossy compression technologies embodied in the MP3.

Advanced Audio Coding - Wikipedia, the free encyclopedia

MP3 - Wikipedia, the free encyclopedia
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I wouldn't convert them to mp3, as it's going to sound crap. You don't want to convert an already compressed audio format into another compressed audio format that's worse than the source which you started with.
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"Ok; but that's a promotional message. Thankfully the Internet has more information and more detailed analysis and advice: Marc Heijligers' Encoding Observations are extensive and offers good analysis of the different formats and bitrates. From his analysis, a 160 kbps AAC file is similar in quality to a 192 kbps VBR MP3 file (with the AAC file weighing in at less than 90% of the equivalent MP3 file size) and that does seem to support Apple's claims about AAC quality. The participants in this discussion over at iPodLounge seem to agree... "


"AIUI, the MP4 files that iTunes sells are all 256 kbps"

So converting all those AAC itunes files to MP3 320 kbps , VBR , would be the way to go . Since they will be about the same quality .
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You don't want to convert an already compressed audio format into another compressed audio format that's worse than the source which you started with.
Yeah but from what the previous posts show is that "a 160 kbps AAC file is similar in quality to a 192 kbps VBR MP3 file " .

If itunes are 256 kbps , than a 320 kbps VBR, MP3 will be at least the same as the AAC file .
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"Ok; but that's a promotional message. Thankfully the Internet has more information and more detailed analysis and advice: Marc Heijligers' Encoding Observations are extensive and offers good analysis of the different formats and bitrates. From his analysis, a 160 kbps AAC file is similar in quality to a 192 kbps VBR MP3 file (with the AAC file weighing in at less than 90% of the equivalent MP3 file size) and that does seem to support Apple's claims about AAC quality. The participants in this discussion over at iPodLounge seem to agree... "


"AIUI, the MP4 files that iTunes sells are all 256 kbps"

So converting all those AAC itunes files to MP3 320 kbps , VBR , would be the way to go . Since they will be about the same quality .
That sounds like a common sense compromise -- as long as the devices you want to play the resulting MP3's all support VBR! Hopefully, more do now. But, for instance, my mom's ~2005 Toyota Avalon's CD player doesn't play VBR MP3's. (Car tech tends to lag, of course.)

Re-rendering lossy-compressed files into a different -- even higher -- lossy-compression format is never a first-choice option, seems to me. But if you have a format that's frozen out of some players, what other choice is there?
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If itunes are 256 kbps , than a 320 kbps VBR, MP3 will be at least the same as the AAC file .
If they were both being ripped from the same source (from CD), then perhaps. But in your case, you're not going to be doing that.

You're converting an already converted file into another lossy format. You can try it on a few songs, and if the quality is acceptable to you, then I guess all is good. It's kind of like making a cassette copy of a cassette, each generation will be worse sounding than the previous and less of the original will be there and more artifacts introduced.
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If they were both being ripped from the same source (from CD), then perhaps. But in your case, you're not going to be doing that.

You're converting an already converted file into another lossy format. You can try it on a few songs, and if the quality is acceptable to you, then I guess all is good. It's kind of like making a cassette copy of a cassette, each generation will be worse sounding than the previous and less of the original will be there and more artifacts introduced.
Well that sucks .

Whats the best file to convert it to then ? WAV ? But then won't it will be a large file of whats really only 256 kbps . Kinda like recording a VHS tape onto a DVD . Yeah its on a DVD but its still looks like a VHS tape .
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I would never use vbr anymore.

I used to use vbr for my own songs and I would always send them to a friend of mine, he always said they sounded ok.. One day I was over his house and played one of the mp3's I sent him and to my shock it sounded like crap, his mp3 player was showing some were encoded at 116 kbps others seems to be encoded around 64 kbps and so on. You can't count on someones player being updated and supporting vbr, so go 320 or 256 or even 192 and play it safe. It may not be the best but at least they're more reliable than vbr.

that's my story anyway..
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Well that sucks .

Whats the best file to convert it to then ? WAV ? But then won't it will be a large file of whats really only 256 kbps . Kinda like recording a VHS tape onto a DVD . Yeah its on a DVD but its still looks like a VHS tape .
Yes, converting it to WAV or any other non-lossy format would basically be a waste of space, as the quality would never be better than the source, which is a 256kbps AAC file.

Your VHS tape to DVD analogy is correct, that's what it would be like converting an AAC into a WAV. And to further expand on the analogy, converting an AAC into MP3 is like recording a VHS tape onto another VHS tape.

I assume that you have some MP3 player that doesn't play AAC? Without buying different hardware that actually plays back AAC, I guess that you probably don't have many other choices available to you besides converting the AAC files to MP3, and hope that the quality is acceptable for listening purposes.
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Well that sucks .

Whats the best file to convert it to then ? WAV ? But then won't it will be a large file of whats really only 256 kbps . Kinda like recording a VHS tape onto a DVD . Yeah its on a DVD but its still looks like a VHS tape .
I'd go with the 320 kbps mp3 CBR (assuming all the players in question will play that -- some older players would top out at 128 kbps (!) or maybe somewhat higher rates but not play even 256 or 320 CBR.)


I'll bet the degradation isn't too noticeable, particularly with consumer-grade converters like those in a car, phone, media pod, etc.

(When I was using a subscription service that had media in what I estimated to be 128-168 kbps quality range, it didn't seem to matter whether I listened over my motherboard built-in (SigmaTel) audio or my outboard MOTU box. When I switched to MOG's all-320 kbps streams, the difference between converters was 'suddenly' noticeable -- so noticeable that if I forget to switch, I'll typically find myself thinking, wait, things sound kind of dull, here... Of course, that's the other way around from your situation -- but it highlights the fact that differences in media files may not matter much unless the output converters are up to a certain quality level.)
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Alright thanks guys for helping figure this out . Looks like is probably gonna be 320 kbps mp3 CBR (instead of VBR) .
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Yes, converting it to WAV or any other non-lossy format would basically be a waste of space, as the quality would never be better than the source, which is a 256kbps AAC file.

Your VHS tape to DVD analogy is correct, that's what it would be like converting an AAC into a WAV. And to further expand on the analogy, converting an AAC into MP3 is like recording a VHS tape onto another VHS tape.

I assume that you have some MP3 player that doesn't play AAC? Without buying different hardware that actually plays back AAC, I guess that you probably don't have many other choices available to you besides converting the AAC files to MP3, and hope that the quality is acceptable for listening purposes.
Well the problem is he has a bunch of music downloaded from itunes but the new player he got is not an ipod , I forget what it is , but it won't play stuff from itunes , because of the DRM I guess embedded in the files . So hes gotta convert it to something else so the player can play these songs downloaded from itunes . Also just get them in a format that can play on pretty much anything .
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