4 Replies Latest reply on Mar 5, 2010 7:12 AM by the_wine_snob

    Frustrating audio sync problem with MJPG clips!

    GusFields

      I make short films from our family trips, using the jpg:s and mjpg clips made with our Canon compact digital camera. This has worked fine (since PE 2). Now I often get a frustrating audio problem on SOME of the MJPG:s, SOMETIMES.

       

      When I play the clip in PE7, after 0.5 - 1 sec the audio jumps back to start, before it continues to the end along with the video. This makes the audio out of sync with the video (lagging 0,5 – 1 seconds).

       

      The only way to fix this is to separate the audio track from the video, cut the start of the audio (to where it jumps back to the start) and then move the audio track to make it in sync. Besides being a tedious way to do on all clips, the audio track is not possible to extend “in the other end”, so I have to cut the video at the end as well…

       

      However, this is not happing on all MJPG clips but only on some.

      Also, the clip looks fine in other programs, e.g. wmp or windows movie maker.

       

      I have tried other MJPG decoders but that does not make any difference (so it’s obviously no problem with the video). The audio is PCM Audio 44100Hz, 706 kb/s mono.

       

      Now, when I tried repairing the PE7 installation, updating DirectX, removing all caches in the project directory, rebooting, it worked! The clip I was testing was in sync!

       

      But, the next day I noticed the sync problem again on a lot of other clips… I then thought I should try to force PE to reanalyze the video again, so I remove the cache-directories (did not help) and moved the project file to another directory (this did not help, but on the other hand, I didn’t see PE7 analyzing the video again, so maybe there is a cache somewhere else??)

       

      I noticed (looking at properties on the clip in the preview window in PE7), that the original audio is 44100Hz mono, but PE7 converts it to 48000Hz mono. Don’t know if there is some problem there, but it should not be any difference on different clips from the same source… (and the “jump back” in audio is 0,5-1 seconds regardless of clip length, and not the 9% that the difference in frequency would suggest + the audio plays in “normal speed”).

       

      I’ve run out of ideas!!

       

      Please, does anybody have any constructive ideas or tips on what to try? Are there more caches to clear? Are there conflicts with another program, like wmp?

       

      (I use PE 7.0 on a 4Gb, quadcore system running Windows Vista Home Premium 64 bit.)

       

      // G

        • 1. Re: Frustrating audio sync problem with MJPG clips!
          nealeh Level 5

          GusFields wrote:

           

          I make short films from our family trips, using the jpg:s and mjpg clips made with our Canon compact digital camera. ... I noticed (looking at properties on the clip in the preview window in PE7), that the original audio is 44100Hz mono, but PE7 converts it to 48000Hz mono. ... but it should not be any difference on different clips from the same source…

          PRE does not work well editing video from digital photo cameras.

          The 48000Hz audio conversion is normal.

          Re Clips from the same source please run one working and one not working through the application GSpot and post screen captures here.

           

          Ideally convert the footage to DV-AVI before loading to PRE. See What tools can I use to convert my video to DV-AVI?

           

          Cheers,
          --
          Neale
          Insanity is hereditary, you get it from your children

          • 2. Re: Frustrating audio sync problem with MJPG clips!
            Steve Grisetti Adobe Community Professional

            I definitely agree with Neale.

             

            Most people find success converting MJPEG-AVIs to DV-AVIs with Windows MovieMaker, using the steps in the link Neale posted.

            • 3. Re: Frustrating audio sync problem with MJPG clips!
              GusFields Level 1

              Thanks, I suppose I can start batch-converting my mjpg movies before importing them inte PE7, if that would make this problem disappear. I'll try that (I have FormatFactory installed, but VirtualDub seems like a nice tool if that is better), although that would make the process a bit more long-winded...

               

              Regarding GSPOT info on a file that works and one doesn't, there are typically no difference between them (except length and content, of course). In fact, as I mentioned above, the same movie did not work until I did some reinstalling, clearing caches etc. Then the same movie suddenly worked OK again.

               

              I attach the GSPOT info on that file.

               

              MVI_1895_gspot.jpg

               

              (I never had this problem on my older XP system that run PE2...).

               

              I will try converting to see if the problem disappears.

               

              Thanks!

               

              // G

              • 4. Re: Frustrating audio sync problem with MJPG clips!
                the_wine_snob Level 9

                The 44.1KHz mono should not be a problem. Yes, internally, PrE will first Conform that to 48KHz 32-bit Floating Point for editing, but as 44.1KHz is a standard (THE standard for CD Audio), Adobe programs can read that, and Conform fine - in most cases.

                 

                I am a big fan of batch converting, and since I only do SD Projects, will always choose DV-AVI Type II w/ 48KHz 16-bit PCM/WAV Audio. I use a shareware converter, because it offers me rapid batch conversion, and never fails me with some really odd footage, but there are several freeware programs, that get high marks from users here.

                 

                Recently, I had a handful of WMV's, and got lazy. PrE will Import most WMV's, so I just loaded them up. Bad move! Things took so very long, even on a very fast system. Minutes stretched into hours. When finally done, I did the same edit with the WMV's converted to DV-AVI's and it was 5x faster with the same exact quality. For the time it would take to have a big cup of coffee, during the batch conversion, I could have saved many hours of processing time. I knew the proper workflow, as I espouse it here all of the time to others. I broke my "golden rule," and paid the price, 'cause I got lazy. I think that I posted the exact times in a thread I started, to re-enforce the benefit of converting outside of the NLE, so that others could learn from my error.

                 

                Good luck,

                 

                Hunt