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Thread: .m4a to mp3 and bitrates?

  1. #1

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    .m4a to mp3 and bitrates?

    i have some music in .m4a format at 192kbps that i want to convert to mp3. i have the codec for it. my question is this-what bit rate should i convert the mp3's to? 192 bit like the m4a source? i realize you cant get more quality out of something than what it has, but when i do convert it to 192 bit the file is slightly smaller than the original. Just wondering what to do. thanx

  2. #2
    dBpoweramp Guru ChristinaS's Avatar
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    Re: .m4a to mp3 and bitrates?

    Stay at the same bitrate. The mp3 file size may be a bit smaller than the m4a one, simply dure to differences in encoding method - and maybe size of tag information too. The bitrate determines the quality. Don't go to a higher bitrate as that's useless.

  3. #3
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    Re: .m4a to mp3 and bitrates?

    But if you're transcoding from a lossy format to a different lossy format, wouldn't you want to pick at least the next higher preset bitrate so as not to lose that much quality?

  4. #4
    dBpoweramp Guru xoas's Avatar
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    Re: .m4a to mp3 and bitrates?

    I think that Neil's opinion is valid-sometimes.

    The theory is this:
    Any audio file is always its own best copy. In thhis case the m4a file cannot be improved. It can be duplicated through Windows. You can make a lossless copy (which will be much largeer in size). Or you can convert it to a different lossy format, in this case mp3. The mp3 file will never be as good as the 192 kbs m4a file.

    This being said, it should be obvious that mp3 copies of the m4a made at different bitrates will themselves vary in quality. Say you convert the m4a file to mp3 at 64 kbs and at 160 kbs. You should expect to find a difference and you will. Likewise, if you convert the m4a file to mp3 at 320 kbs, you should expect to find a better copy of the m4a file than the two other mp3 files (at 64 kbs and at 160 kbs). It will not be a better file than the original 192 kbs m4a file. The other drawback of the 320 kbs mp3 file will be again that it is much larger than the m4a file (although not as large as a lossless copy would be).

    So there might be some advantage to converting the m4a file to a higher quality mp3 file. The question raised by Kada20 is whether there is indeed an advantage to this and if so, what would be the optimal bitrate. Here I have two ideas to offer for this type of situation.

    The first relies on a certain amount of experience and theory. It is accepted that wma files encoded at a (especially) low bitrate (say 64 kbs.) is equivalent in quality to the same audio encoded to mp3 at 96 kbs. So if I wanted this degree of quality when encoding, but I want to use mp3, I would be advised to encode the audio directly to mp3 at 96 kbs. If I started out with the wma file at 64 kbs and I wanted to convert it to mp3, my feeling is that I would want to convert the 64 kbs wma file to mp3 at 96 kbs.

    Likewise, my hunch is that if you ripped audio to m4a at 192 kbs. and to also mp3 at different bitrate setting, you might find the m4a superior to 192 kbs mp3 but that as you increase the quality of the mp3 encoding there will be a point where the encoded mp3 file is roughly equal to the m4a file at 192 kbs and that by the time you get the mp3 encoding to 320 kbs the mp3 file will sound better. My guess is that mp3 will start sounding roughly equal to 192 kbs m4a when the mp3 is encoded around 220-240 kbs. This is an estimate on my part because I have not done the listening comparison to confirm this. But assuming this estimate is correct, my suggestion would be to convert the 192 kbs m4a file to around 220 to 240 kbs mp3.

    The other idea is that not every theoretical difference is an important difference. If Kada were to take m4a files ripped at 192 kbs with mp3 files ripped from the same sources at 192 kbs, Kada might find no significant difference between the two. If that is the case, there is no particular reason for Kada to convert to mp3 higher than 192 kbs. and I would be in agreement with Christina. If the original sources for the m4a files is unavailable, then I would recommend that Kada try converting a few m4a files at 192 kbs to mp3 at 192 kbs, at around 220 kbs and around 240 kbs, and maybe at 160 kbs. Then Kada's task would be to compare these various copies primarily to try to find either the point where there is no discernable difference from increasing the mp3 bitrate, or finding the lowest mp3 bitrate with the best fit for the original m4a file.

    So I think it is up to Kada to decide whether it would be more Kada-licious to convert to a the same bitrate (as Christina suggests) or at a slightly higher bitrate (as Neil suggests). I'd be interested in knowing what Kada ends up deciding.

    Best wishes,
    Bill

  5. #5
    dBpoweramp Guru ChristinaS's Avatar
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    Re: .m4a to mp3 and bitrates?

    Well, that would give one a false sense of having improved the quality when in fact no such thing has been achieved. There's always extra loss when going from lossy to lossy. Best it is to judge each case separately. Some files can take several transcodings quite OK, others will have been transcoded so many times that the end even at a higher bitrate will sound quite poor. The thing is if you have to convert to another format you have to balance the need with the want. It all comes down to space vs quality. To keep the best quality you can have only convert once to a lossless format compatible with the device and leave it so.


    LOL! I took so long to write this profound paragraph :p that Bill had the time to give a truly logical explanation :D
    Last edited by ChristinaS; 08-22-2005 at 11:44 PM.

  6. #6

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    Re: .m4a to mp3 and bitrates?

    First off, thanx for all your fast replies and help. I think i will take the advice of maybe converting to the 220 range. I did do some conversion at the 320 level but couldnt really discern any noticable difference either good or bad and since i want to cram as much as possible on one disk, the 220 range sounds like a good compromise. :smile2:

  7. #7

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    Kbs?

    Hello all
    Can someone please let me know if it is better to have more or less KBS?

  8. #8
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    Re: Kbs?

    More if you have the disk space.

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