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Thread: What's in the container?

  1. #1
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    What's in the container?

    Hi people

    I have the following (technical) question and no matter how hard I google, I can't seem to find the answer.

    - What is inside the FLAC container that stores the sound. My understanding is that WAV holds PCM through the RIFF format.
    - Does what the container contains differ for compressed FLAC versus uncompressed FLAC?
    - Could you store PCM inside the FLAC container?
    - What does DBPoweramp actually put in the FLAC container for both compressed and uncompressed FLAC?

    Yes, probably highly technical but now that I am about to rip my CD collection and replace my CD player with a streamer / DAC combo, I'd like to understand what I am looking at :-)

    Thanks!

  2. #2
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    Re: What's in the container?

    I have never actually looked, all I know is that for flac the compression options can be disabled, however flac might still encode the data differently (in that AIFF and WAVE have different encodings).

  3. #3
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    Re: What's in the container?

    Does this help?

    http://xiph.org/flac/format.html

    Mike

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    Re: What's in the container?

    Quote Originally Posted by Michael Sargent View Post
    Yes and no :D It's interesting but I don't know what it all means and how it compares to the WAV and AIFF containers. Some of it is a bit above my head to be honest.

  5. #5
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    Re: What's in the container?

    Quote Originally Posted by PepsiCan View Post
    Yes and no :D It's interesting but I don't know what it all means and how it compares to the WAV and AIFF containers. Some of it is a bit above my head to be honest.
    I found some more information.

    • It seems FLAC supports RIFF chunks (which is what WAV uses) but no information as to whether this is what Uncompressed FLAC is using and/or whether the RIFF chuncks are compressed or not or whether they are used in uncompressed FLAC only or all FLACs.
    • It seems FLAC supports unencoded LPCM (same as WAV and AIFF use). But no confirmation as to whether this is what is used in uncompressed FLAC or something else.
    • There are tags in the FLAC specification that allow the decoder to bypass the decompression routines (which I assume is the big difference between compressed and uncompressed)
    • Another interesting thing is that FLAC compression level 0 is still significantly smaller than FLAC uncompressed (as per someone else's test that I found via Google)


    Also, it seems that RIFF chunks are handled differently in FLAC than in WAV. With WAV (so I am told by Google) the RIFF chuncks are simply knitted together after the metadata is cut off to form a PCM stream. But with FLAC, because there is more metadata and/or it is attached to the chunks differently, it is less straightforward to combine the chunks to a LPCM. But I have been unable to confirm this.

    Any further ideas or pointers anyone?

  6. #6
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    Re: What's in the container?

    RIFF is not used in flac to store audio.

  7. #7
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    Re: What's in the container?

    Quote Originally Posted by Spoon View Post
    RIFF is not used in flac to store audio.
    Then what is? Is it LPCM chopped up in blocks?

  8. #8
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    Re: What's in the container?

    Seems like the FLAC forum at hydrogenaudio.org would be the perfect place to get technical FLAC questions answered. (not complaining about posting here, just pointing out where an answer may be available)

    http://www.hydrogenaudio.org/forums/...p?showforum=67

  9. #9
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    Re: What's in the container?

    Quote Originally Posted by PepsiCan View Post
    Then what is? Is it LPCM chopped up in blocks?
    If you want a detailed answer, see this http://xiph.org/flac/features.html but if you want a simplistic answer, it consists of PCM samples where redundant information like repetitions is compactly coded (imagine ABCABCABCABC becoming 4xABC)
    Last edited by AndrewFG; 04-30-2014 at 05:34 AM.

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