14 Replies Latest reply on Jan 1, 2011 5:37 PM by the_wine_snob

    Audio Sync question

    admin@norcalmotocross.com

      I am going to be doing some interviews and will be using an external audio device(not sure what yet), but my question is do I have to worry about getting an audio device that records at the same frame rate as my camera in order to sync them later?  If I am at60fps on my camera, but the audio is recording at 30, is that going to cause issues?

        • 1. Re: Audio Sync question
          the_wine_snob Level 9

          Even if the specs. of your device matches that of your camera (on paper), you will likely have to experiment to get the right tweak to the Audio to match 100%. The audio and camera mfgrs. do not seem able to get crystals that match 100%.

           

          As an example, one trusted user here found that with his external audio recorder, he needed to adjust its output files by 103%, IIRC. That was the difference between the real output from his recorder and his cameras, though they matched "on paper."

           

          Now, with crystal clocks, once you find the correction factor, that should ALWAYS work, so one set of tests, SHOULD be enough.

           

          In the old cine days, we just hooked up the camera and the recorder by wire, and chose to use the crystal in one, to control the other - usually the camera set the frequency for the Nagra, and it would signal when it had received, processed and locked onto the sync of the camera. Obviously, that was THEN, and also required a wired connection.

           

          Good luck,

           

          Hunt

          • 2. Re: Audio Sync question
            Jim_Simon Level 8
            The audio and camera mfgrs. do not seem able to get crystals that match 100%.

             

            Which I still find confusing, because all the camera makers use clocks that sync perfectly.  Even using different brands of DV cameras, they will stay in sync across a full hour of DV tape.  Seems entirely possible for audio device makers to do the same.  It's very frustrating that they don't.

            • 3. Re: Audio Sync question
              norcalmotocross Level 1

              I was afraid it was going to be tough.  The cameras have decent mics on them, maybe I will use a second camera hidden from sight somehow just to record the audio.

               

              I am using GoPro HD heros.  They are not really made for what I am doing, so I will need to improvise and try and deal with in post. 

              • 4. Re: Audio Sync question
                the_wine_snob Level 9

                Though it does not address your question here, this ARTICLE might have some useful tips on the Go-Pro footage. IIRC, the author was dealing with specific G-Pro, and was also editing in PrElements, not PrPro, but still might have a tip, or two?

                 

                Good luck, and looks like a lot of folk ARE using the Go-Pro's.

                 

                Hunt

                • 5. Re: Audio Sync question
                  the_wine_snob Level 9

                  Jim,

                   

                  How far off was I with the "103%" correction?

                   

                  I also agree with you. If my patio clock can "phone home" to Boulder, CO, and set it's time to the atomic clock there, the mfgrs. SHOULD be able to get things to match, 100%. Just does not make sense to me, but then I am old and dumb.

                   

                  Hunt

                  • 6. Re: Audio Sync question
                    Jim_Simon Level 8

                    Clips from my audio device actually require an adjustment of 100.04%.

                     

                    It's a very small adjustment, but over an hour long wedding ceremony, it adds up.

                    • 7. Re: Audio Sync question
                      the_wine_snob Level 9

                      Jim,

                       

                      Thanks for that correction. I will try to remember that number (better, than I obviously did).

                       

                      Appreciated,

                       

                      Hunt

                      • 8. Re: Audio Sync question
                        shooternz Level 6

                        Just for the record

                         

                        Profesional recording devices and recordists have no problem synching double system sound without any fudge workarounds.

                         

                        Suggest the above but do ask why is the camera not suitable for the task and you have chosen to use a separate recoreder?.

                         

                        It does entail more work for the editor.

                        • 9. Re: Audio Sync question
                          norcalmotocross Level 1

                          My original question was more of a research question.  I have to work with the GoPro camera.  That is a self imposed requirement of the project.  The mics dont work that well, but like I posted, I am going to try and hide one off camera slightly or crop in post processing to hide it.  My plan is to put it on the subjects lap.

                           

                          Ill let you know how it goes.

                           

                          Thanks for the ideas.

                          • 10. Re: Audio Sync question
                            Jim_Simon Level 8

                            Profesional recording devices...have no problem synching double system sound without any fudge workarounds.

                             

                            That likely only applies if you change the first word in the sentence to "expensive".  But I don't want to pay as much (or more) for my audio recorder as I did for my camera.  It does a whole lot less than my camera, I should pay a whole lot less (and still get a properly timed recording).  But "reality" doesn't seem to jive with what "should be".

                            • 11. Re: Audio Sync question
                              shooternz Level 6
                                But I don't want to pay as much (or more) for my audio recorder as I did for my camera.

                               

                               

                              Easily fixed .

                               

                              Get an expensive audio recorder...then get an even more expensive camera.

                               

                              The world will be in balance and you will have two things that work properly ... as they should.

                              • 12. Re: Audio Sync question
                                the_wine_snob Level 9

                                You know, I had NOT thought of that approach, but upon a second reading, do see the wisdom...

                                 

                                 

                                 

                                Happy January 12th down there, or is it still the 11th?

                                 

                                Hunt

                                • 13. Re: Audio Sync question
                                  shooternz Level 6

                                  2nd January 2011 down here Bill.

                                   

                                  Happy New Year to you.

                                  • 14. Re: Audio Sync question
                                    the_wine_snob Level 9

                                    Thanks for that. I still can't get my feeble head around it. When booking the aborted flight to Sydney, I almost got blind-sided by the "Arrives 2 days later." Two days later? I'm not sure that I'd live that long.

                                     

                                    Happy New Year, and thanks for the laugh.

                                     

                                    Hunt