Author Topic: Poor Audio Cuts?  (Read 624 times)

BatmanLoko9

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Poor Audio Cuts?
« on: October 09, 2018, 05:52:22 AM »
Hi, I've been using and liking Avidemux for quite a while, but something I've noticed is the program often gives imprecise and imperfect cuts of audio, where things don't really line up as they should.

Here's what I mean. This is the clip in Avidemux, pay close attention to the end audio:
https://youtu.be/cWrvT_wc-6I
These are the exact same frames but edited in Premiere Pro:
https://youtu.be/MYszxgSq1h0

In Premiere Pro, you get the full audio. It doesn't cut off early like Avidemux. Why is this? Am I doing something wrong? My encode settings are
video: mpeg4 ASP (ff)
Audio: AAC (lav)
Output: mp4v2

I have tried all different audio formats and none were as clean as Premiere Pro, even "copy". Could anyone test this out by trying to get precise cuts of their own? I have encountered this many times across different videos. It's like Avidemux mutes the very end but I don't understand why. Please move this to the right section if I've posted it in the wrong one.

Thank you
« Last Edit: October 09, 2018, 09:56:20 PM by BatmanLoko9 »

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #1 on: October 09, 2018, 06:19:40 AM »
This might be related to A/V sync. Did you try the latest nightly? Why DivX? This codec is ancient. Please try the Mp4 muxer, not mp4v2 for better comparison.

https://avidemux.org/nightly/
« Last Edit: October 09, 2018, 06:21:48 AM by eumagga0x2a »

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #2 on: October 09, 2018, 07:40:59 AM »
This might be related to A/V sync. Did you try the latest nightly? Why DivX? This codec is ancient. Please try the Mp4 muxer, not mp4v2 for better comparison.

https://avidemux.org/nightly/

Thank you very much for the response. I actually use Avidemux 2.6.21. I have some issues with 2.7. For instance, when I resume playback, I always get a green screen that flashes first. The cut points also work differently in 2.7, in previous versions you'd have to go the next frame and then choose that as the cut off point, 2.7 has you select the last frame you want as the cut off point, which I don't really like.

Regardless, I downloaded the latest nightly as you suggested and used the same settings, except this time had the Output Format set to MP4. Unfortunately, I got the same result. Avidemux 2.7 also seems to have a bug where the beginning of the video has a little audio blip, so it doesn't seem too suitable for my use.  You can hear it here, as well as see that the audio still cuts off poorly:
https://www.youtube.com/watch?v=ttZDmzSCamI


Any ideas? Are others able to replicate this when aiming for precise cuts? I am using Windows 7, but I have previously had these issues on Windows 10 also

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #3 on: October 09, 2018, 08:24:22 AM »
Also, I'm not sure how much this helps, but here's the ending audio tracks for both
Top two are the Avidemux 2.7 mp4 encode
Bottom two are Premiere Pro

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #4 on: October 09, 2018, 12:39:41 PM »
Of course, you must ensure that A/V sync is correct. You could try if disabling B-frames makes the problem disappear.

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #5 on: October 09, 2018, 04:22:21 PM »
The possibly relevant location in code would be the part of the muxerFFmpeg::saveLoop function following avidemux_core/ADM_coreMuxer/src/ADM_coreMuxerFfmpeg.cpp:556.

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For instance, when I resume playback, I always get a green screen that flashes first.

This is pure cosmetics, isn't it? Might be related to the DXVA2 video accel.

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The cut points also work differently in 2.7, in previous versions you'd have to go the next frame and then choose that as the cut off point, 2.7 has you select the last frame you want as the cut off point, which I don't really like.

Well, I see it other way round, so WONTFIX. You could become an important Avidemux contributor, then modify the behaviour to your liking.

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Avidemux 2.7 also seems to have a bug where the beginning of the video has a little audio blip, so it doesn't seem too suitable for my use.

I strongly doubt that this issue (I tried to locate and to solve it, yet without success) is specific to 2.7.x. It is a small amount of previously decoded audio in a buffer, so if the last thing you played in Avidemux was silent, you would avoid this audio blip.

All fixes go only into 2.7.x and later, obviously. So staying at 2.6.21 is not a solution.

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #6 on: October 09, 2018, 06:27:35 PM »
I hope, the tentative fix doesn't break stuff. As to my brief testing, it solves the issue with last bits of audio in the saved video missing when the video stream contains B-frames for libavformat based muxers (Mp4, Matroska, not mp4v2).

Once a new nightly gets generated and uploaded, please test and report back.

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #7 on: October 09, 2018, 09:04:05 PM »
Of course, you must ensure that A/V sync is correct. You could try if disabling B-frames makes the problem disappear.

Sorry, I'm not really sure how to do this, or how to modify the code. 

The possibly relevant location in code would be the part of the muxerFFmpeg::saveLoop function following avidemux_core/ADM_coreMuxer/src/ADM_coreMuxerFfmpeg.cpp:556.

This is pure cosmetics, isn't it? Might be related to the DXVA2 video accel.

Yeah, it just effects playback, not the output but it seems worse in 2.7 than it was in 2.6

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Well, I see it other way round, so WONTFIX. You could become an important Avidemux contributor, then modify the behaviour to your liking.

I completely understand that, I didn't mean to be disrespectful, I was just stating my preferences. Unfortunately I don't know enough to learn how to do that, this is just a program I've enjoyed using for a long time but have had these issues I never understood. I will move on to updated versions eventually, but at the moment for me, 2.7 doesn't offer more than 2.6.

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I strongly doubt that this issue (I tried to locate and to solve it, yet without success) is specific to 2.7.x. It is a small amount of previously decoded audio in a buffer, so if the last thing you played in Avidemux was silent, you would avoid this audio blip.

All fixes go only into 2.7.x and later, obviously. So staying at 2.6.21 is not a solution.

The issue does seem specific to 2.7. I have uploaded 3 more clips to demonstrate the problem.

Here is the clip from Avidemux 2.6:
https://youtu.be/1EggraTCgIw

Here is the same clip but in Avidemux 2.7:
https://youtu.be/2sHpk28Q7oY

And here is the same clip but cut in Premiere Pro:
https://youtu.be/_YgF61Dkk1Y

As you can hear, in 2.7 there is a little audio hitch in the beginning, which isn't present in the other 2 cuts despite starting and ending on the exact same frames. It doesn't happen all the time, sometimes 2.7 behaves fine, but other times I have issues like this.
Also, as before, Premiere Pro gets the full, complete audio, whereas Avidemux seems to cut off early. Is there anything I can really do to fix this, and get precise cuts? I uploaded the audio tracks above if they're of any help.

I really do like Avidemux, it's a brilliant program but I just can't wrap my head round this issue and would like to solve it somehow.

Thanks for all the help

« Last Edit: October 09, 2018, 09:11:43 PM by BatmanLoko9 »

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #8 on: October 09, 2018, 09:10:41 PM »
I hope, the tentative fix doesn't break stuff. As to my brief testing, it solves the issue with last bits of audio in the saved video missing when the video stream contains B-frames for libavformat based muxers (Mp4, Matroska, not mp4v2).

Once a new nightly gets generated and uploaded, please test and report back.

Ah, sorry, I didn't see this post before making my previous one. Should I just wait for the next nightly and see if that works?

I do however want to bring attention to some of the other issues I mentioned with 2.7 in my previous post though, such as the initial audio blip that occurs in some cuts and is present in the video I posted above. The flashing green screen for playback is also problematic, as 2.6 seemed to handle this better, but it is not a major issue.
Have you been able to replicate them, or know of a fix?

Apologies if it sounds like I'm complaining too much, Avidemux has actually served me very well and like I said, I really do like it

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #9 on: October 10, 2018, 09:21:44 AM »
Absolutely no problem with complaining, thank you for raising the question. I actually wanted to encourage to "get hands dirty" and start contributing to shape things to one's liking, at least this is how it worked in my case.

By the way, the only notable change in Avidemux behaviour since the old 2.6.x days when deleting a portion of video was inclusion of the picture matching the B marker (the end point) if it happend to be the last picture of the video. Apart from that, a few changes were made to keep the current position in the video (the currently displayed picture) during editing operations as good as possible to follow the principle of least surprise.

The audio blip is a small portion of the previously decoded audio. I tried to fix it, but it turned out to be quite a difficult task. As explained above, play a silent passage in Avidemux directly before starting a save operation which includes re-encoding of audio. This will result in the blip consisting of silence and thus not noticeable.

If the green flash bothers you, disable DXVA2 display and use the OpenGL (QtGl) output (or feel encouraged to fix the issue yourself!). I get a brief initial corruption when initializing playback using VDPAU as well, but this doesn't bother me. This stuff is not on my todo list.

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Should I just wait for the next nightly and see if that works?

Yes, exactly.

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #10 on: October 11, 2018, 12:11:44 AM »
Absolutely no problem with complaining, thank you for raising the question. I actually wanted to encourage to "get hands dirty" and start contributing to shape things to one's liking, at least this is how it worked in my case.
It does seem interesting, but all of it seems way above my head! It'd be nice to try and manually restore the older B marker behaviour but I seriously would have no idea how to  ;D
 
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The audio blip is a small portion of the previously decoded audio. I tried to fix it, but it turned out to be quite a difficult task. As explained above, play a silent passage in Avidemux directly before starting a save operation which includes re-encoding of audio. This will result in the blip consisting of silence and thus not noticeable.

Do you have any idea why the audio blip is present in 2.7, but not present in 2.6? Is it related to the changes made to follow the principle of least surprise? It just seems strange to me, and unfortunately my use for Avidemux requires lots of precise cuts like this. Sorry, just to be clear, what do you mean by playing silent passages in Avidemux? Is that something that is easy to do and replicate?
As I said, I use Avidemux for stuff like this constantly, so if I have to use a workaround each time I want to make a new clip, or if that audio blip is going to be present when I make a clip, the newer versions of Avidemux may unfortunately be unsuitable for me.
I do not want this to be the case, as I think the program is truly fantastic, but should the blips persist it wouldn't really allow me to do what I want to and I may have to stop using it  :'(
 
I still look forward to the new nightly, and I'm incredibly appreciative you took the time and effort to not only look into this, but fix it as well, You're great, it's just that the blip doesn't seem like it'd be easy to workaround if I'm making multiple cuts at a time.
 
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If the green flash bothers you, disable DXVA2 display and use the OpenGL (QtGl) output (or feel encouraged to fix the issue yourself!). I get a brief initial corruption when initializing playback using VDPAU as well, but this doesn't bother me. This stuff is not on my todo list.

I'll try this, thanks. It doesn't bother me too much either, it just seems more noticeable on 2.7 than it was on 2.6 so I thought maybe it was something on my end.

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #11 on: October 11, 2018, 07:42:11 AM »
I actually wanted to encourage to "get hands dirty" and start contributing to shape things to one's liking, at least this is how it worked in my case.
It does seem interesting, but all of it seems way above my head!

This is always this way initially.

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It'd be nice to try and manually restore the older B marker behaviour but I seriously would have no idea how to  ;D

Could you please explain what you exactly mean here? There were zero changes WRT markers affecting deletions after 2.6.20/21 you are using. Earlier changes affected only deletion of a portion of video with the marker B at or after the last frame. The old behaviour made it impossible to delete the last frame.
 
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The audio blip is a small portion of the previously decoded audio. I tried to fix it, but it turned out to be quite a difficult task. As explained above, play a silent passage in Avidemux directly before starting a save operation which includes re-encoding of audio. This will result in the blip consisting of silence and thus not noticeable.

Do you have any idea why the audio blip is present in 2.7, but not present in 2.6?

No, I am not that familiar with audio code. I am also not sure it was not present in 2.6. This might depend on audio decoder in use and even the audio output (the latter won't affect the saved video, however).

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Is it related to the changes made to follow the principle of least surprise?

Unlikely.

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Sorry, just to be clear, what do you mean by playing silent passages in Avidemux?

The blip consists of the last audio (about ~50 ms in duration) decoded before stopping playback. If playback was stopped during a loud passage in the video, you might get an audible noise in the saved video. If playback was stopped during an almost silent scene, there shouldn't be any perceptible defect.

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if I have to use a workaround each time I want to make a new clip, or if that audio blip is going to be present when I make a clip, the newer versions of Avidemux may unfortunately be unsuitable for me.
I do not want this to be the case, as I think the program is truly fantastic, but should the blips persist it wouldn't really allow me to do what I want to and I may have to stop using it  :'(

As mentioned before, I tried to fix it and failed so far. If the Author of Avidemux doesn't fix this small problem himself, I plan to return to this bug at a later time, once much more important issues are solved. If you need Avidemux to work exactly as you need without workarounds right now, contribute code which fixes this bug (find and pay a capable developer to do it for you) or use another video editor.
 

BatmanLoko9

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Re: Poor Audio Cuts?
« Reply #12 on: October 12, 2018, 01:29:37 AM »
Why do i get an error when trying to post? It brings up a Forbidden error and tells me to enable javascript, but I have. No add ons running either, it's very strange.
 
This is always this way initially.

Have you past programming experience? Without that it seems like it'd be quite difficult to get into this, no?
 
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Could you please explain what you exactly mean here? There were zero changes WRT markers affecting deletions after 2.6.20/21 you are using. Earlier changes affected only deletion of a portion of video with the marker B at or after the last frame. The old behaviour made it impossible to delete the last frame.
I just meant like I said  in an earlier post:
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The cut points also work differently in 2.7, in previous versions you'd have to go the next frame and then choose that as the cut off point, 2.7 has you select the last frame you want as the cut off point, which I don't really like.
You mentioned this was changed as well
 
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No, I am not that familiar with audio code. I am also not sure it was not present in 2.6. This might depend on audio decoder in use and even the audio output (the latter won't affect the saved video, however).

hmm, what makes you think it was not present in 2.6? I uploaded 2 different clips, both showed the blip in 2.7 but not in 2.6. You do have to listen out for it, but it is noticeable in my opinion.
 
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The blip consists of the last audio (about ~50 ms in duration) decoded before stopping playback. If playback was stopped during a loud passage in the video, you might get an audible noise in the saved video. If playback was stopped during an almost silent scene, there shouldn't be any perceptible defect.
Ah I understand what you mean now. Unfortunately like I said my use means I do this quite a bit so can't really hope for quiet scenes.
 
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As mentioned before, I tried to fix it and failed so far. If the Author of Avidemux doesn't fix this small problem himself, I plan to return to this bug at a later time, once much more important issues are solved. If you need Avidemux to work exactly as you need without workarounds right now, contribute code which fixes this bug (find and pay a capable developer to do it for you) or use another video editor.
Yes, I'm very grateful you took the time to look into it and try to fix it, that was really nice of you. I understand your point though, I just came here wondering if I was doing something wrong or if there was a workaround, since i couldn't seem to find mention of the issues elsewhere. I have learnt a bit more as well, so it was very nice of you to take the time to discuss this.  Thanks for all the help, I'll still look out for the next nightly
« Last Edit: October 12, 2018, 01:32:32 AM by BatmanLoko9 »

eumagga0x2a

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Re: Poor Audio Cuts?
« Reply #13 on: October 12, 2018, 07:55:38 PM »
Have you past programming experience?

No past coding experience whatsoever.
 
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I just meant like I said  in an earlier post:
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The cut points also work differently in 2.7, in previous versions you'd have to go the next frame and then choose that as the cut off point, 2.7 has you select the last frame you want as the cut off point, which I don't really like.
You mentioned this was changed as well

If it ever were this way, I would classify this as a clearly buggy behaviour. Usually, one sets the B cut point to a keyframe using UP/DOWN arrow keys. In copy mode (which is the default), we can't drop B, it must stay. The way you wish the delete operation to work, one would have to make an additional step just to avoid a corrupted video (and a menacing warning popping out) in the most common use case.

The behaviour was changed only for B at or past the last frame of the video – and for a good reason.
 
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I just came here wondering if I was doing something wrong or if there was a workaround

There is a workaround for the blip :-)

The issue will be tackled one day – maybe.

BatmanLoko10

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Re: Poor Audio Cuts?
« Reply #14 on: November 17, 2018, 11:10:38 AM »
It's me again, I have created a new account as I wanted to update this thread. I think there was an issue with the email I used for the previous account, so I received constant errors. I attempted to use a different email and even that wasn't accepted but I appear to have the issue sorted out now.

I just wanted to update. I've been testing with the latest Nightly, and it seems the problem has been fixed now!

The audio blip has unfortunately remained. and I have a weird issue when encoding with Mpeg4 ASP (ff). If I encode a video using those settings, and then open the video in certain programs like Premiere Pro, or Windows 10 Media Player, it plays/encodes like this:
https://youtu.be/FEVCIUuu5GA
 
I don't understand why it does this. If I play the clip in VLC, or just upload the clip straight to Youtube, it is absolutely fine. However, in certain programs like Premiere Pro, or Windows own media player, the entire video is distorted.

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Audible in the saved video when played with another video player (e.g. vlc) or audible when played in Avidemux? If the latter, you might be hearing the popping sound from initializing the audio device, not relevant to the actual content of the audio track. If the former, does enabling audio shift and using a bigger and bigger negative value (i.e. advancing audio WRT video) remove the blip?

Sorry, I meant audible in another video player. I will hopefully test using audio shifts later and report back
 
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No, unless I get a good way to reproduce it and there are no tasks with higher priority.
It just seems like strange behaviour. If you wish, I could provide you with the source files, as well as the exact frames where I get this blip if you do want to look into it. Regardless, I appreciate all the help so far even if you can't.
 
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No idea, but if you really have to use an obsolete codec like H.263, you could try whether the Xvid encoder shows better compatibility with non-ffmpeg based decoders.
Do you think it would be better to just use Mpeg4 x264 then? Like I said, I don't know much about video encoding, but way back when I first started using Avidemux, I used to encounter a cut in audio when I'd use x264, which is why I used MPEG4 ASP (ff) encoder. I know that seems strange, given it's the video encoder but it's just the way it was.
I will switch to x264, I assume it's less obsolete and if I encounter the audio cut I will again report back.
Thank you