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S.Lundin
Inspiring
August 12, 2024
Question

Audio sync using external dig recorder

  • August 12, 2024
  • 2 replies
  • 1037 views

Hi,
I use a Nikon Z7ii and a Zoom H1e digital recorder.
About one in five of my cam audio files will not synchronize(Premiere Pro synchronize fuction) with the audio WAV from the H1e digital recorder.
In every case there are obvious sync patterns in the audio amplitude plots and I manually sync them.
But this adds a lot of time to my work.

ffprobe34 reports the camera audio as:
Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 256 kb/s (default)
It reports the H1e audio WAV as:
Stream #0:0: Audio: pcm_f32le ([3][0][0][0] / 0x0003), 96000 Hz, 2 channels, flt, 6144 kb/s

I have studied the Premiers Pro manual and looked at too many youtube and forum posts with no answer.
It is a requirement for me to use the H1e audio. It is significantly better than the camera. The camera does not have any options to set audio sample rate or bit rate.
I've looked into possible timecode issues but don't understand the language used in the manual about timecodes.
The camera does have the timecode generation option set. It starts at zero for each clip.
When I manuall sync the dig recorder I find that I have to unset the snap magnet and slip the audio by amounts less than a frame.
Any thoughts, reference links or suggestions are appreciated.

Hapy Trails

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    2 replies

    P
    PaulMurphy
    Community Expert
    August 12, 2024

    Is Premiere able to find sync using Clip > Create Multi-camera Source Sequence?

      S
      S.LundinAuthor
      Inspiring
      August 14, 2024

      Thanks Paul and Neil. I tried to use Create Multi-cam... but it failed.  That was not easy as Create-Multi... only works on video with audio; not audio by itself. The menus were greyed out.  But all this got me thinking. What I have found is the Premiere is clipping my 32bit floats when it reads them in.  I used an old tool of mine (CoolEdit 2000) to normalized it to -3dB (based on exmination of the max dB) the 32 float before putiing it into Premiere. I just did my first test and the WAV 32bit float that was normalized before reading into Premiere synchronized as I would expect.  When I examined the previous 32 float inputs in Premiere I could see they are being clipped at 0dB.  My files are typically going to +3dB.  I need to test some more of my older files but this may be my new workflow. (FYI, CoolEdit 2000 was purchased by Adobe and became Audition).   If the peaks are the most significant part of the sync algorithm then that may be why it is failing.  I have some interesting images of the wave forms but am low on time for a few days.  I'll try to make another post showing what I have seen.  First, I need to go back to some files from spring and early summer to verify this is a fix.

      Happy Trails

       

      S
      S.LundinAuthor
      Inspiring
      August 15, 2024

      Audition can process the clips as well, but you can also quickly normalize audio directly in Premiere.

      Go to Clip > Audio Options > Gain, then choose Normalize All Peaks to -3 dB.


      Audition should have all that is in my old CoolEdit and more. I think it would do work. I am still looking at older files to see if the normalizing is the panacea.  When I look at the wave forms they look very different.  One mic is one the stage floor at the edge between the audience and the other is on my camers wherevery I may be (5-20ft back). I'll get 20-30 more tests is the next four days.  I stuck on this for now and can't just stop.  Now I'm questioning the differences in 'normalization' techniques.  They are not normal.

      R Neil Haugen
      R Neil Haugen
      Brainiac
      August 12, 2024

      If the levels between the two files are significantly different Premiere will struggle. For the ones not matching, select and hit G (gain) and maybe set to -6dB max peak.

      Everyone's mileage always varies ...
      S
      S.LundinAuthor
      Inspiring
      August 12, 2024

      Thanks for the tip. I tried to noralize (several times for peak and all) the external recorder and the video sound track but Premiere still has trouble with the 32bit float file from the H1e.  But that got me thinking about the H1e file.  I converted the H1e file (32 bit 96kHz) to 32 bit 48kHz with ffmpeg. That file will synch to the video sound track every time.  At max zoom-in the 96k and 48k audio tracks do look very different. My eye can sync them but the 'synchronize' code must have troubles with the differences. The 32 bit float is new for me and Adobe may need time to catchup with it.

      Happy Trails

      R Neil Haugen
      R Neil Haugen
      Brainiac
      August 12, 2024

      Yes ... 32 bit float audio is a bit of a challenge yet. Although we're told that Premiere works with it natively just fine, many users do report difficulties in a fair number of things. Including multicam work and syncing audio at the top of the list.

       

      Hoping we do get better practical results with 32 bit audio in the future.

      Everyone's mileage always varies ...
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