Why am I getting audible pops between audio edits?

Davlon
Davlon Posts: 283 Just Starting Out
edited February 2018 in Post-production techniques

Both in comp shots and on the timeline, I am now getting audible pops between audio edits.

- On the timeline, at the end of one comp shot and the beginning of the next shot, a slight popping noise is clearly audible.   

- While building a comp shot, as I'm editing the narration, when I use the cut tool to add a pause, I hear a definite click or micro-pop sound.

Sometimes I'm able to get rid of it by changing the length of the audio segment a few frames.  Otherwise, this is a new problem. The noise is there, even in the rendered video.

The audio source is a CAD GXL 2400 condenser mic.  I've been using it on many projects and it's never given me a problem.  In several places the talent seems to have  been brushing the mic, so there is mic rumble, but other than that the track is clean.

(For those of you looking for a great mic, this one is worthy of your consideration -- excellent value)

 ---

Okay -- I'm editing my post.  I listened to the track again and cranked up the silence.  The talent's computer fan is raising the noise floor of the track.  But should this cause audio pops?  Do I have to manually add audio fade-outs and fade-ins between cuts? That's a major hassle.  Is there a noise gate filter/setting?

 

 

Comments

  • NormanPCN
    NormanPCN Posts: 4,081 Enthusiast
    edited February 2018

    Hitfilm does not do very good on audio edits, in my experience, if the sound is not really silent on any cut or really fast fade. You get the pops. I does not always happen in all circumstances, but it does happen. I've never done/tested clip cuts in Hitfilm but I have used the volume keyframe bar for fast fasts to duck sound. An abrupt drop/raise of volume like with a cut. Hitfilm needed a few frames, yes frames, on the fade duration to not pop. Contrast this with Vegas which on the same media could do sub frame "quick fades" without pops. There is an old thread on this forum somewhere about pops. Not really on edits, but on quick fades normally used in ducking audio.

    I don't know what Hitfilm does with actual audio clip edits (cuts and such). Vegas always insert a quick fade (user preference duration) when you do a cut. This to avoid pops I assume. You can edit/remove them and you may get pops. The Hitfilm UI does not show such things.  Hitfilm could do such a quick fade of clip cuts under the covers. Who is to say.

  • Davlon
    Davlon Posts: 283 Just Starting Out

    Is this called a bug? It's mighty annoying/completely maddening the more I repeatedly shift the edit points in both cuts to find the golden non-pop microsecond.

    And it's costing me time that I can't bill for, because it's a defect on my end.

    @Triem23 is there a bugs list in addition to a wish list?

  • Triem23
    Triem23 Posts: 20,059 Ambassador

    Nah, it's not a bug. As Norman says, pops  could be fixed by having Hitfilm automatically inserting a 1ms fade in/out at all audio edits. The reason Vegas does the fades is why you have the pops.

    Consider this simple sine wave diagram. 

    https://upload.wikimedia.org/wikipedia/commons/thumb/0/03/Zero_crossing.svg/1200px-Zero_crossing.svg.png

    Note the point marked as a "zero crossing." This is the point in an audio waveform where there is a lull in vibration--a zero amplitude point in the wave. If a waveform isn't sliced at a zero-point there will be a pop. Since Hitfilm (and other NLEs cut at video frame boundaries, you usually miss the zero point. Which is, of course, why Vegas does the 1ms fades. To create zero points.

    So, not a bug. Hitfilm isn't doing anything incorrect or malfunctioning. Just missing a feature it should have--short audio fades at all audio edges. 

    This has all been oversimplified a bit, but it's accurate enough. 

  • Davlon
    Davlon Posts: 283 Just Starting Out
    edited February 2018

    @Triem23   Has the issue been noted?  Has a fix been requested?  

    Clean audio is a pressing need for every production of every sort.  What "@" names do I need to place here to get someone's attention?  We all need this fixed now.

  • NormanPCN
    NormanPCN Posts: 4,081 Enthusiast

    I'll add one slight correction to @Triem23 s post. The Vegas quick fade defaults to 10ms. Not 1ms. It is a user option in preferences.

    @Davlon I don't know about issues with clip trimming reported, but the pops on short fades causing pops was noted by @CedricBonnier in this previous thread. If you have an issue then it is always best to contact support directly. This is a user forum. FxHome staff do monitor and reply at times but don't count on it.

    In a couple of quick test I can't seem to get pops on cuts. I can get a problem with quick volume bar audio raises from ~mute(-60). One frame fades had a problem, three frame was fine. Volume cuts seemed okay in my minor test. I can't tell exactly which media and timecode I showed in that thread. It is publically available media from Hitfilm.

    I tried a few quick cuts on a music file and all seemed fine.

  • CleverTagline
    CleverTagline Posts: 3,315 Ambassador

    @Davlon When editing your original post, you pointed out that "The talent's computer fan is raising the noise floor of the track. But should this cause audio pops?"  Naturally it will.  A raised noise floor means you have a higher level of ambient noise between lines of dialog.  Because you can hear a sound in those gaps (albeit very quiet sound), there's still a waveform.  To avoid pops when cutting such audio, you either have to find zero crossing points to cut at, or you have to manually fade the audio before you cut.

    If you end up with VO that has a high noise floor, you (or your voice talent) can process the audio in a dedicated audio editing program and use what's sometimes referred to as a downward expander.  In short, it's essentially a compressor-like tool that takes quiet stuff and makes it even quieter.  The Mac has a built-in Audio Units effect called AUDynamicsProcessor, which is basically a combination of a compressor and downward expander in one.  I use this for all of my VO tracks, but I'm also super picky during VO editing and often trim the gaps between lines so there's literally no sound there.  The downward expander takes care of the transitions between silence and speech, and my picky editing cleans up the rest.  That way I can cut at any break in the speech and know that there's complete silence there, so pops won't happen.

    Having such tools directly in HitFilm would be nice, but the tools already exist in audio software, so I suggest using what's there to fix any problems, then bringing your clean audio into HitFilm.

    Ultimately, the greatest responsibility for clean audio begins at the source.  Get your VO guy to give you cleaner audio, or find a new guy who will.  :)

  • Davlon
    Davlon Posts: 283 Just Starting Out
    edited February 2018

    @jsbarret

    > Ultimately, the greatest responsibility for clean audio begins at the source.  Get your VO guy to give you cleaner audio, or find a new guy who will. 

    Yep.  I've never had a problem as bad as this before.  And thank you Norman and Mike for your input.

  • Tdiddy
    Tdiddy Posts: 18

    I am not positive this is the same issue I am having but didnt want to start a new thread. I am getting "pops" over audio transitions. It only seems to happen when I have some sort of "cross" transition between cuts, it seems to be at random and I cant quite isolate the cause. It is almost as if the video transitions are being picked up by the audio (if that makes any sense). This has been annoying me for awhile, I will export a transition and link here later for an example...unless someone knows an easy solution.

  • Triem23
    Triem23 Posts: 20,059 Ambassador

    @Tdiddy you have the same issue discussed above with same implications and solutions. 

  • Dharmashivali
    Dharmashivali Posts: 2
    edited August 2018

    I'm adding a comment because i have the same issue, on an audio speech record, sometimes on silence there are some ambient noises, so i look for a good flat silence segment, copy and paste it on every ambient noise, so i can emulate a silence, i don't know if i make myself clear on the solution i use. So the tick or pop appears in the union of these segments of audio, it also appears at the final render. i don't use cross transitions, only copy and paste audio segments moved one next to the other.