Niku
Level 2 (305 points)
Mac OS X

Q: Identifying audio formats

I once thought that the distinctions between the different audio formats were simple, No more. The more I read, the more confused I become, so I'm hoping that it is not really necessary to know ALL of the details to make intelligent choices.

 

"Container formats. concatenated, prepended with ADTS headers, raw, codecs, ID3 tags, encapsulators, AAC, M4A, MPEG-4, etc". Maybe I don't need to know all that stuff. What I really want to know is what format is on my CD. After mounting it on my desktop, I get two different readings from two different tools. Media-Info says the following (condensed): Size 45.0 MB, Format QuickTime/MPEG...JPEG 2000format, Meta info>Type audio, codec aac,  fourCC  mp4a.

Right-clicking on the CD icon produces the following: Format CD audio, Capacity 268.4MB, Available 2.5MB, Used 265.9MB on disk.

 

I don't know what format "CD audio" is. If it has a meaning that everyone agrees with, that would be helpful. Also, how can it be that Media-info says the CD size is 45.0MB while the right-click says 265.9MB?

iPad (4th gen) Wi-Fi, iOS 9.3.1, null

Posted on Sep 7, 2016 4:01 PM

by dialabrain,Solvedanswer
dialabrain dialabrain
Level 5 (5,935 points)
Mac App Store
A:

Yes, it can be very confusing.

Posted on Sep 7, 2016 4:07 PM

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Niku

Q: Identifying audio formats

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  • by dialabrain,Solvedanswer

    dialabrain dialabrain Sep 7, 2016 4:07 PM in response to Niku
    Level 5 (5,935 points)
    Mac App Store
    Sep 7, 2016 4:07 PM in response to Niku

    Yes, it can be very confusing.

  • by Niku,

    Niku Niku Sep 7, 2016 4:34 PM in response to dialabrain
    Level 2 (305 points)
    Mac OS X
    Sep 7, 2016 4:34 PM in response to dialabrain

    My understanding is that AAC, M4A, And MPEG-4 (more?) are kinda, sort of, in-a-way, the same, but that there are some differences. I also believe that the differences,in most cases, are not of importance to someone who is not a technician. So, until someone straightens-me-out, I'm going to any that AAC=M4A=MPEG-4. However, I would still like to know what format my CD contains and how large the audio file is.

  • by dialabrain,Helpful

    dialabrain dialabrain Sep 7, 2016 4:56 PM in response to Niku
    Level 5 (5,935 points)
    Mac App Store
    Sep 7, 2016 4:56 PM in response to Niku

    One is giving you the capacity of the CD and telling you it's a CD Audio disk, the other is the size of the audio file on the CD and what its format is.

  • by Niku,

    Niku Niku Sep 7, 2016 4:45 PM in response to Niku
    Level 2 (305 points)
    Mac OS X
    Sep 7, 2016 4:45 PM in response to Niku

    I also just noticed that Media-info says the CD contains a kind of MPEG, aac, and MP4A (a variety or synonym for M4A?). Well, that's all of them. So my Cd has variants of all three formats?

  • by dialabrain,

    dialabrain dialabrain Sep 7, 2016 4:51 PM in response to Niku
    Level 5 (5,935 points)
    Mac App Store
    Sep 7, 2016 4:51 PM in response to Niku

    No, your CD has one file and one format. You should look up MPEG, AAC and M4a.

  • by Niku,

    Niku Niku Sep 7, 2016 4:56 PM in response to dialabrain
    Level 2 (305 points)
    Mac OS X
    Sep 7, 2016 4:56 PM in response to dialabrain

    Hmm. I guess the two tools give different readings because Media-info is telling you about the RECORDING on the CD, while the right-clicking is providing information about the physical characteristics of the CD. The latter information would be more useful for someone who was planning to record something into the CD. Maybe that's it, because I can think of no other reason why anyone would want to know the capacity of the CD. I'd have to say that the right-click does not provide sufficient information. If you're recording something from a CD, you want to know how big the file on the CD is, not the capacity of the CD. If I'm overlooking something, please let me know. Anyway, I'm glad that I now have Media-info.

  • by Niku,

    Niku Niku Sep 7, 2016 5:03 PM in response to dialabrain
    Level 2 (305 points)
    Mac OS X
    Sep 7, 2016 5:03 PM in response to dialabrain

    Looking up that subject leads to confusion. I've done it. I'm done doing that. However, I would like you to read what Media-info says. It mentions three formats. I suppose they are all variants of AAC but that they somehow play different roles. The confusion disappears if you're willing to accept that AAC=MPEG-4=M4A=MP4A=Who knows what else?

  • by Niku,

    Niku Niku Sep 7, 2016 6:28 PM in response to Niku
    Level 2 (305 points)
    Mac OS X
    Sep 7, 2016 6:28 PM in response to Niku

    Well, I guess it's up to me. So, I'll have to say that, for all practical purposes, my CD uses the  AAC (actually CD audio) format and the file on it is 45MB. That's  not what I had expected when I had the CD made from my vinyl record, but I didn't know any better. I had expected the recording to be in an uncompressed format so that I could better use it to edit the recording. So, when I was told that it would be in the AAC format, I assumed that AAC was an uncompressed format. That was wrong. AAC is compressed. It is AIFF and WAV that are uncompressed. Anyway, not all is lost. I think it is possible to edit (delete clicks and pops) from AAC/CD audio files, but if that is  not possible, I will create a WAV or AIFF file from my vinyl record myself. I might even do it regardless of the AAC/CD audio results for the experience.