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What's in the container?

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  • PepsiCan
    dBpoweramp Enthusiast
    • Apr 2014
    • 106

    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!
  • Spoon
    Administrator
    • Apr 2002
    • 44080

    #2
    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).
    Spoon
    www.dbpoweramp.com

    Comment

    • Michael Sargent
      dBpoweramp Enthusiast
      • Dec 2009
      • 134

      #3
      Re: What's in the container?

      Does this help?

      A free, open source codec for lossless audio compression and decompression


      Mike

      Comment

      • PepsiCan
        dBpoweramp Enthusiast
        • Apr 2014
        • 106

        #4
        Re: What's in the container?

        Originally posted by Michael Sargent
        Does this help?

        A free, open source codec for lossless audio compression and decompression


        Mike
        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.

        Comment

        • PepsiCan
          dBpoweramp Enthusiast
          • Apr 2014
          • 106

          #5
          Re: What's in the container?

          Originally posted by PepsiCan
          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?

          Comment

          • Spoon
            Administrator
            • Apr 2002
            • 44080

            #6
            Re: What's in the container?

            RIFF is not used in flac to store audio.
            Spoon
            www.dbpoweramp.com

            Comment

            • PepsiCan
              dBpoweramp Enthusiast
              • Apr 2014
              • 106

              #7
              Re: What's in the container?

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

              Comment

              • garym
                dBpoweramp Guru
                • Nov 2007
                • 5763

                #8
                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)

                Comment

                • AndrewFG
                  dBpoweramp Enthusiast
                  • May 2010
                  • 59

                  #9
                  Re: What's in the container?

                  Originally posted by PepsiCan
                  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; April 30, 2014, 10:34 AM.

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