8 Replies Latest reply: Aug 21, 2012 4:11 PM by Jay Moore RSS

    SB adds silence to beginning of mp3s when saving

    wcPublish Community Member

      I'm trying to create loops, and I'll notice SB adds silence at the beginning during "Save Loop As"—there will be an audible hiccup. But it seems to happen with smoothing on and off whenever I save out as a mp3. Some of the files are perfectly loopable when they come in as a wav, so it's infuriating that SB is so keen on meddling.

       

      I can trim the beginning and resave, but I know I shouldn't be resaving an mp3. Anyone else having this problem?

       

      "Why Soundbooth, why?!"

        • 1. Re: SB adds silence to beginning of mp3s when saving
          ryclark Community Member

          It's not just Soundbooth, Audition does as well. It is due to the way .mp3s are compressed. They are compressed using blocks of data. If your data doesn't quite fill a block it has to be padded out with zeroes. Hence the gap. mp3 isn't a good compressed format for loops. Ogg or similar work much better if you can't keep the full .wav file.

          • 2. Re: SB adds silence to beginning of mp3s when saving
            _durin_ Employee Hosts

            ryclark nailed it.  The analogy I've used before is trying to fill up a row of glasses with a pitcher of water.  When you get to the last glass, the water only fills it partway, but there's still additional empty volume in the glass.  mp3 encoding is the same - blocks are reserved to hold the data.  if there's enough data to create a new block, but not enough to fill it, the rest is padded with 0's.  Usually, to compensate and minimize this in order to prevent long silences, the 0's are split evenly between the beginning and end.

            • 3. Re: SB adds silence to beginning of mp3s when saving
              wcPublish Community Member

              Thanks to both of you. I no longer blame Sound Booth, but it seems like there is a market for some function that would facilitate easy gapless mp3 loops.

               

              This is for an iphone app, so WAVs are an option. But they're big even when fully compromised. But I've shown my developer the steps from  http://www.compuphase.com/mp3/mp3loops.htm , he's going to have decide what the best practice is.

               

              Or I may have to find all new music that is sparse enough to mask the silence at the transition.

              • 4. Re: SB adds silence to beginning of mp3s when saving
                _durin_ Employee Hosts

                Adobe Audition has supported a format called .CEL which was an mp3 loop with some additional metadata indicating the start and end point in order to skip the silence buffers.  I'll put a feature request in the database to consider adding this support to Soundbooth and Flash as this issue comes up from time to time.  It would be nice to use the solution we already have in one app.

                • 5. Re: SB adds silence to beginning of mp3s when saving
                  Jay Moore Community Member

                  The biggest reason you have silence at the beginning of mp3's is because of encoder delay. Encoders that use a time/frequency domain to store audio data will always have a bit of delay when encoding files. Since the frequency-transforms are done in fixed-size blocks...it's required to add some silence so the audio can be encoded in it's entirety. Generally the beginning is padded so the audio ends on a block, however, without taking this gap in for account, a decoder will treat it as audio. Likewise, when the file is decoded, the decoder can add a bit of delay.

                   

                  The biggest problem with mp3 is the amount of delay will vary encoder to encoder and it makes no standard way of defining the gap. The CEL format as mentioned adds one format of metadata to allow mp3 samples to be gapless, likewise, the LAME encoder can add it's own format of gap information, and no, Audition is not able to read or do anything with the LAME gap metadata.

                  • 6. Re: SB adds silence to beginning of mp3s when saving
                    MyKingdomforaScreenName

                    SBCS5 adds silence to WAVs as well, which are uncompressed. It also adds silence to WMA files. This is unprofessional and unacceptable for software in this price range.

                    For free, you can get Audacity, which can save MP3 files with no added silence in the beginning. Download here: http://audacity-download.org/

                    Why does freeware perform better than your high-priced professional software, Adobe?

                    Sorry for digging up a very old thread in the forum, but SBCS5 still has this problem, so it is relevant.

                    • 7. Re: SB adds silence to beginning of mp3s when saving
                      SarahNorthway Community Member

                      For free, you can get Audacity, which can save MP3 files with no added silence in the beginning.

                       

                      Not true! Audacity DOES add silence to the beginning of MP3 files just like everything else - I just tried it.

                       

                      http://www.compuphase.com/mp3/mp3loops.htm works for most tracks (although it didn't like the extra garbage Audition adds to WAV format, I had to resave in Audacity), but still leaves a (briefer) gap at the beginning of some files. The only way I've found to get perfect looping is to import the wav into Flash Pro and tell it to use MP3 format. This results in compressed mp3 format with no gaps, but you can't produce an MP3 file from it, only SWF or SWC.

                       

                      So why does the Adobe's animation suite get perfect looping mp3s when their professional sound editor doesn't?

                      • 8. Re: SB adds silence to beginning of mp3s when saving
                        Jay Moore Community Member

                        Here's a protip for you guys:

                         

                        *everything*, and I mean *everything* adds a bit of silence to an mp3. It's called pre-delay. It's built in to the mp3 encoders. Some encoders, mostly Lame, are able to write in the tag how much pre-delay is added by the encoder so that software that can read it will know how much to offset.

                         

                        You can not avoid this pre-delay with the mp3 format; in fact, I don't think it's really avoidable with *any* lossy formats; it's just some formats added provisions to mark how long this pre-delay is.

                         

                        The  animation suite probably either reads the track and detects pre-delay, or is able to read the information from the encoder. The point is; the reason the professional sound editors don't are...they're professional sound editors. What a shock. They weren't designed for people who don't know anything about audio; they were designed for professional audio engineers, who are more than  well aware of the pre-delay in mp3 encoders (or should be).

                         

                         

                        As far as silence to wavs...it sounds like you're saving an mp3 as a wav without deleting the gap.