David Esp Video Technical Blog

UpdateL

• {See my later post on this, at http://blog.davidesp.com/archives/923}

Context:

• I’m producing a video of a progressive rock band (Panic Room) playing at a party on-board a lightship…
• The video has been edited in Adobe Premiere, initially in version CS6 and then in CC7.0 (105), the latter via opening the CS6 project-file.
• The Premiere project structure is: [ Master_Sequence > Multicam_Sequence  > Sync_Sequence > Raw_Footage (XDCAM-EX) ].

Problem:

• While previewing a complete draft of the video, that had been Exported from Premiere CC, I noticed a repeat, after 2 seconds, of the “big finish” of one of the band’s songs.  The repeat is quieter than the “real” (wanted) one.

Investigations:

• The problem occurs when editing, but only at the Master_Sequence level.  It does not occur at the Multicam_Sequence level.
• In the Multicam_Sequence, near to the problem part of the audio. is a Crossfade transition.  If I delete that Crossfade (leaving the audio transition to be a plain Cut) then the problem (at Master_Sequence level) no longer occurs.
• The repeated element of audio is not that within the Crossfade transition, it is instead from a (short) clip (resulting from multicam editing) almost immediately preceding the transition.
  • This is suggestive of a memory issue, such as cache (RAM or file) or buffer (presumably RAM).
• It feels to me like this is a bug in Premiere CC, broadly similar to something I once encountered (in a different project) in Premiere CS6.
• I often encounter bugs when I go “off-piste” as compared to most people’s editing procedure, presumably due to programmers/testers not having thought similarly “off-piste”.
• The only potentially (?) unusual thing I did in the edit of the Multicam Sequence was at certain places to cut just the audio track (via [C-Razor] tool, having selected only the audio part via [Alt-LeftClick].
  • The reason I did that was to separate the end of a song from the following applause etc., which was much quieter, to allow Clip:[Audio Gain > Normalize] to be carried out separately on that applause.  Then I added [Crossfade > Constant Power] in order to smooth the join to the applause.
  • I used this approach rather than Volume envelope because:
    • Audio Gain can increase gain by any amount, whereas Volume Envelope’s maximum gain appears to be 6dB.
      • Possibly the 6dB limit might be configurable in Preferences (I just saw a setting suggestive of that but haven’t tried it),
    • It is very convenient and less “messy” than fiddling about with Envelopes and Track Width etc.
• Experiments:
  • As stated earlier, if I delete that [Crossfade > Constant Power] (leaving the audio transition to be a plain Cut) then the problem (at Master_Sequence level) no longer occurs.
  • If I replace the crossfade with [Crossfade > Constant Gain] then it makes no difference (the problem remains).
  • If I delete the multicam sequence element (audio & video) penultimately preceding the transition, i.e. the element containing the “big finish”, leaving a gap (black silence) then when I play the Master Sequence, the gap faithfully appears as expected but then the “repeat” (of the “big finish”) nevertheless happens.
    • By “penultimately” I mean not the clip that is the left-hand part of the transition, but the clip before that (which is not therefore any part of the transition).
  • If instead I delete only the audio part and then drag the previous audio (only) part forwards (in time) to fill the gap, then when I play Master Sequence, the “repeat” now comes from the end of what is now a different “previous clip” (the one that was prior to the one I just deleted).
  • This tells us the repeat comes from whatever clip is penultimate to the Crossfade audio transition, it does not happen only for one clip in particular.
  • …to be continued… (sadly)

WebSearch:

• e.g. Google:[adobe premiere audio repeating], [adobe forum]
  • http://forums.adobe.com/community/premiere
    • (nothing relevant found, and today {and next few days} was unable to sign-in, presumably due to Adobe web system maintenance)
    • {BUT see my later post on this: http://blog.davidesp.com/archives/923}
      • Solution that worked:
        • Open the Cut-Sequence, i.e. the one where I cut between various multicam angles etc.
        • Menu:[Sequence > Render Audio]
          • This was extremely fast, almost instantaneous, worth doing on a regular basis in future…
  • http://helpx.adobe.com/premiere-pro/kb/audio-video-glitches-avchd.html
    • Covers a number of issues but not mine.
    • Recommends sufficiently powerful CPU and in the case of spanned file-structure footage (like AVCHD or presumably XDCAM-EX), transcoding to a straight format like DNxHD or UT.
  • http://forums.adobe.com/thread/1047591
    • Strange audio problem in Premiere Pro CS6 (Aug 10, 2012)
    • Problem: All material has been shot on the Sony FS 100 camera – imported into PP with the Media Browser. In one interview the last part of a clip has corrupted audio. At one point on the timeline the audio stops playing, and it sounds like a scratch on a vinyl record – two words repeating themselves to the end of the clip (See screenshot of timeline). The images are as they should.
      • Sounds very similar to my problem.
    • Solution: (Delete) everything within both the /Media Cache and /Media Cache Files folders…
      • BUT when I tried that, in my case it made no difference…
  • http://blog.flickharrison.com/2012/04/problem-solving-in-adobe-premiere-audio-glitches-and-sync/
    • Problem-Solving in Adobe Premiere: Audio Glitches and Sync (Apr 7, 2012)
    • Problem:
      • I imported a few camera cards full of AVCAM / AVCHD footage from my HMC-150 and edited for a few days.  Then I clicked on one imported clip and found that the audio was wrong.  Glitches, skips, out of sync, weird things happening – all nice sounding, but not in the right places.  I checked the original MTS files on my HD using VLC player.  Sound was fine, everything was in sync.
    • Solution:
      • For each imported clip in .mts format, Premiere adds a file with the same name with .xmp as the extension in the same folder.  Feeling bold, I quit Premiere then deleted all these the .xmp files for that card – though i didn’t empty my trash yet.  I re-opened Premiere and double-clicked that file.  It was dead silent, as clips often are when first imported to Premiere.  It does some meta-data-ing… and then the sound was all back in proper order, problem solved.
      • The XMP files had been re-produced in that folder, although this time, apparently, without glitches.
      • {The poster of this solution appeared slightly concerned, at least initially, about the addition of [.xmp] (sidecar) files into the file-structure, as indeed I had reported e.g. at http://blog.davidesp.com/archives/901, but (like me) didn’t do anything about it, just bore the fact in mind}
    • {Doubts:
      • In my case, the file itself plays fine in Premiere, it’s only when nested that the problem arises, hence I doubt the same solution would fix my problem
        }
  • ??