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TOPIC: Audio spike at a cut

Re: Audio spike at a cut 1 year, 10 months ago #125179

  • donkpow
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Sonic Visualizer.

What are the source audio tracks? AAC, Mp3, wav, ...? The screen grab shows 3 audio sources, correct?
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Re: Audio spike at a cut 1 year, 10 months ago #125181

  • hugly
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I see 4 Audio channels, I guess (!) two stereo streams, one stream for the music and one for voiceover. A3,A4 is grouped, A1,A2 isn't.


EDIT:
I don't know about the source formats. I guess A1,A2 aac linked with the video, A3,A4 seperately imported from compressed media (which would mean wav in Lightworks). This is only wild speculation.
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Last Edit: 1 year, 10 months ago by hugly.

Re: Audio spike at a cut 1 year, 10 months ago #125182

  • donkpow
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hugly wrote:
I see 4 Audio channels, I guess (!) two stereo streams, one stream for the music and one for voiceover. A3,A4 is grouped, A1,A2 isn't.


EDIT:
I don't know about the source formats. I guess A1,A2 aac linked with the video, A3,A4 seperately imported from compressed media (which would mean wav in Lightworks). This is only wild speculation.
Okay, my bad. There is a language barrier here. I say "track", it means complete recording with 1,2,3,4,5,6,... channels. I see one mono track and two 2-channel stereo tracks.

My thinking at this point is the root of the problem is with decoding/encoding the edited streams. It's a pure guess.
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Last Edit: 1 year, 10 months ago by donkpow. Reason: spelling

Re: Audio spike at a cut 1 year, 10 months ago #125183

  • donkpow
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Never mind, I was looking at V1 as an audio track. We have 3 audio recordings, each 2 channel stereo. One voice, one music, and the third looks like ambiance.

I would extend the ambiance track, if that is what it is, into the music track with a cross fade. Also, I would put the music on it's own set of tracks. Not on the same tracks as voice over.

It's really important not to mix formats. If the music is Mp3, get out of it. Use pcm wav for that. Same with the ambiance loop. I understand your screen recording software probably records mp4 with aac. You may get away with aac and wav on the same timeline but aac and mp3 is likely to create problems.
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Re: Audio spike at a cut 1 year, 10 months ago #125184

  • hugly
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I think we did a lot so far. Without knowing sources and OP's support we can't find out what's going on.

Let's see if real interest arrises.
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Last Edit: 1 year, 10 months ago by hugly.

Re: Audio spike at a cut 1 year, 10 months ago #125188

  • donkpow
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Yes. You can eliminate the possibility that the noise is recorded sound and the idea that it is completely digitally created. An interesting fact is that the amplitude ramps corresponding to the waveform and that there are time differences between the left and right channels.


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Re: Audio spike at a cut 1 year, 10 months ago #125190

  • hugly
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If this is induced, which is obvioulsy possible, where is it from?
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Last Edit: 1 year, 10 months ago by hugly.

Re: Audio spike at a cut 1 year, 10 months ago #125194

  • donkpow
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Multiple formats, decode/encode edited streams.
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Re: Audio spike at a cut 1 year, 10 months ago #125209

  • hugly
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Yeah, and maybe some drugs involved too?



>> <<
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Last Edit: 1 year, 10 months ago by hugly.

Re: Audio spike at a cut 1 year, 10 months ago #125214

  • RWAV
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Should stay off them really. What we do know about this 'spike' is that it exists in the original file - so it is not LW generated - and so is of only passing interest.

It would be very good to know which quality version of the original @hugly downloaded - you may recall I declared that I downloaded the 60fps 720p HD version. Hugly's information may add some new depth to this conversation.
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Re: Audio spike at a cut 1 year, 10 months ago #125215

  • hugly
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General
Complete name               : M:\Flohmarkt Funde Pokemon TCG #5 SPECIAL_ Gefälschte Karten_Holo- und Reverse Holo-Karten - YouTube [720p].mp4
Format                      : MPEG-4
Format profile              : Base Media / Version 2
Codec ID                    : mp42 (isom/mp42)
File size                   : 194 MiB
Duration                    : 10mn 44s
Overall bit rate mode       : Variable
Overall bit rate            : 2 528 Kbps
Encoded date                : UTC 2016-09-11 17:13:01
Tagged date                 : UTC 2016-09-11 17:13:01
gsst                        : 0
gstd                        : 644260

Video
ID                          : 1
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : High@L3.1
Format settings, CABAC      : Yes
Format settings, ReFrames   : 1 frame
Format settings, GOP        : M=1, N=60
Codec ID                    : avc1
Codec ID/Info               : Advanced Video Coding
Duration                    : 10mn 44s
Bit rate                    : 2 334 Kbps
Maximum bit rate            : 4 575 Kbps
Width                       : 1 280 pixels
Height                      : 720 pixels
Display aspect ratio        : 16:9
Frame rate mode             : Variable
Frame rate                  : 29.970 (30000/1001) fps
Minimum frame rate          : 29.970 fps
Maximum frame rate          : 30.273 fps
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Progressive
Bits/(Pixel*Frame)          : 0.084
Stream size                 : 179 MiB (92%)
Tagged date                 : UTC 2016-09-11 17:13:08
Color range                 : Limited
Color primaries             : BT.709
Transfer characteristics    : BT.709
Matrix coefficients         : BT.709

Audio
ID                          : 2
Format                      : AAC
Format/Info                 : Advanced Audio Codec
Format profile              : LC
Codec ID                    : 40
Duration                    : 10mn 44s
Bit rate mode               : Variable
Bit rate                    : 192 Kbps
Maximum bit rate            : 201 Kbps
Channel(s)                  : 2 channels
Channel positions           : Front: L R
Sampling rate               : 44.1 KHz
Frame rate                  : 43.066 fps (1024 spf)
Compression mode            : Lossy
Stream size                 : 14.7 MiB (8%)
Title                       : IsoMedia File Produced by Google, 5-11-2011
Language                    : English
Encoded date                : UTC 2016-09-11 17:13:06
Tagged date                 : UTC 2016-09-11 17:13:08

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Re: Audio spike at a cut 1 year, 10 months ago #125218

  • RWAV
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When I listened to donkpow's file late last night - it seems to have a metallic sound - having heard metallic-compression-artefacts often enough I thought perhaps additional audio compression - but no it was just my late night confusion with the snippet of incoming sound after the 'spike'. Shame really - if it had been thus would have kept us busy head-butting for a week or two.

Anyway as in the information below - our file parameters are spookily similar - make one wonder what exactly the YouTube 60fps transcode is - other than a bit of different metadata.
:pinch: Warning: Spoiler!


This morning I loaded into LW donkpow's file and audio extracted as .wav via QT Pro from my download - virtually identical - donkpow's level is a tad higher than the QT Export - that's all. Please see the attached.

To satisfy my curiosity I also download a number of resolutions of that same file from YouTube - I did not expect to see there is virtually no difference in audio compression - to the extent that in my original download audio occupies 5% of file size - in the lowest resolution audio is 54% of the file.
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Re: Audio spike at a cut 1 year, 10 months ago #125221

  • donkpow
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It is my understanding the noise is 'not' in the source file and 'not' apparent in the edit. It only shows up in the export, essentially rendered and compressed file from Lightworks.

That "metallic" sound is electronically generated music. It gave me pause, too, but I wanted to include both sides of the cut.
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Re: Audio spike at a cut 1 year, 10 months ago #125223

  • RWAV
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If we are talking about the noise you described in this topic - then I can hear the noise in the source file playing in FootageStudio4k, VLC and QTPro - at this stage LW has not touched the file. I can hear and see the noise in LW - as illustrated in my post - and which seems to be in exactly the same place and exactly the same noise as in your post. Not sure if I've missed something so far.

1. Have just exported the entire shot in an edit with the LW YouTube setting - still the same noise - no new ones I can detect.
2. Have made an edit where each 30 seconds I insert a cut by deleting 15 seconds of the shot - exported that - a total of 13 cuts - and after than the original 'noise' is still in the edit but there are no 'noises' on any of the cuts points.

Importing the export - and jumping 900 frames - the distance between cuts - on close examination and careful listening across each cued 900 frame point I can neither see nor hear any new noises. The original noise is still there.

Yes the metallic sound did confuse me last night. On reflection - I think the fact the YouTube - which would not give away bandwidth if it wasn't absolutely necessary - does not apply any additional compression to already compressed sound - as described in my earlier post - is possibly an indication of what YouTube thinks of that process. Perhaps LW users might consider that.
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Re: Audio spike at a cut 1 year, 10 months ago #125228

  • hugly
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The ongoing discussion inspired me to check all known facts again.

It is my understanding the noise is 'not' in the source file and 'not' apparent in the edit.

Yes, with the information we have so far I think donkpow is right.

The "spike" shown in OP's screengrab of his edit is also present in the export. The clearly audible spike to the left we analysed above is artificially added. The cause is unknown so far and maybe only reproducible and explainable with the help of OP.
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Last Edit: 1 year, 10 months ago by hugly.
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