Audio length mismatch

bobthevideoman wrote on 12/2/2018, 5:52 AM

I have a problem matching the lengths of video audio with separate audio that was used and recorded at the same time.

My project is a musical show, I always record the video with audio from a mike, then in edit dub over the CD audio for quality reasons. The trouble is this time (I have done it his way for years using Magix) the CD audio will not match the length of the recorded video even though the CD audio was played at the time of recording.

My recorded video properties are = MP4 3840x2160 50 FPS 8bit 4:2:0 - Audio 16 bit 48000 I have imported this video (with sound) into my project which the Magix project properties are = PAL HDTV 1920x1080i 16:9 25FPS

Then I have imported audio via CD. This CD audio was used at the time of recording the video at the show. BUT, after importing, the CD audio track is 7 seconds shorter than the video audio.

Audio import methods:-

The audio was imported to a file on my computer (saved properties = MP3 192 kbps 44100 16 bit)

AND using Magix (Import audio CD Tracks) (saved properties = 44100 16 bit WAV)

Both imported files (MP3 and WAV) are exactly the same length.

I realise that the samples per second are different, but not sure it matters ? If they are how do I import so that they match ?

This has never happened before and I am at a loss to fix it. Please can anyone help ??

Magix Pro X 16.0.2.304

Computer specs:-

i7-4770K

16GB ram

NVIDIA GeForce GTX760

Win 7 64 bit

Comments

Michal-MST wrote on 12/2/2018, 7:50 AM

Try to use AudaCity to convert mp3 to wav. Export values set the same as you have in the video Audio 16 bit 48000

In general, mp3 is a bad way to record sound. As well as the variable bitrate, we ask for trouble. As we record an additional audio track, the sound recording parameters should be identical to those in the camera.

RogerGunkel wrote on 12/2/2018, 8:00 AM

Hi Bob,

The immediate solution that springs to mind is to highlight the CD audio track on the timeline, then right click on it and select the timestretch/pitch option. You should then be able to move the central grid marker to stretch the audio back to the length of the audio on the video track. The difference in speed is unlikely to be noticeable at all.

Roger

bobthevideoman wrote on 12/2/2018, 9:15 AM

Try to use AudaCity to convert mp3 to wav. Export values set the same as you have in the video Audio 16 bit 48000

In general, mp3 is a bad way to record sound. As well as the variable bitrate, we ask for trouble. As we record an additional audio track, the sound recording parameters should be identical to those in the camera.

Thank you Rodger

I tried Audacity, but the converted WAV file is exactly the same length as the original MP3

Bob

bobthevideoman wrote on 12/2/2018, 9:18 AM

Hi Bob,

The immediate solution that springs to mind is to highlight the CD audio track on the timeline, then right click on it and select the timestretch/pitch option. You should then be able to move the central grid marker to stretch the audio back to the length of the audio on the video track. The difference in speed is unlikely to be noticeable at all.

Roger

Thank you Rodger

I shall try your stretch method and let you know how I get on

Bob

bobthevideoman wrote on 12/2/2018, 3:22 PM

Hi Bob,

The immediate solution that springs to mind is to highlight the CD audio track on the timeline, then right click on it and select the timestretch/pitch option. You should then be able to move the central grid marker to stretch the audio back to the length of the audio on the video track. The difference in speed is unlikely to be noticeable at all.

Roger

Thank you Rodger

I shall try your stretch method and let you know how I get on

Bob

Thanks Roger

I did use time stretch and it worked well, you really cant tell the difference.

I am bothered though that I have used the CD method of dubbing many times and never had a problem till now. I have just updated Magix but I dont think it could be that ??

Also, sorry I spelt your name wrong, bit stressed today !!!

emmrecs wrote on 12/3/2018, 3:46 AM

@bobthevideoman

I am bothered though that I have used the CD method of dubbing many times and never had a problem till now

A possible reason: how long, in total playing time, was the original footage? I ask, because I see your separate audio recording you describe as being a "CD", recorded at 44.1 kHz, 16 bit, i.e. "Red Book" (CD) standard. The audio of your video will almost certainly have been recorded at 48 kHz, 16 bit.

When you inserted your CD recording to your VPX timeline, it would have been played back at 48 kHz. Because each second of your CD audio has only 44,100 samples per second and VPX wants 48,000 samples per second, each second your audio is, effectively, getting a little "ahead" of your video because it is taking those extra samples from the "next" second. The longer the overall playback time, the greater that difference will become.

I hope that makes sense!

I'm glad Roger's method worked for you but, personally, I would do as suggested in an earlier post, I would sample-convert the 44.1 kHz audio to 48 kHz before importing it to the VPX timeline. And I would also agree with @Michal-MST that use of an .mp3 version of the audio is best avoided!

HTH

Jeff

bobthevideoman wrote on 12/3/2018, 7:14 AM

@bobthevideoman

I am bothered though that I have used the CD method of dubbing many times and never had a problem till now

A possible reason: how long, in total playing time, was the original footage? I ask, because I see your separate audio recording you describe as being a "CD", recorded at 44.1 kHz, 16 bit, i.e. "Red Book" (CD) standard. The audio of your video will almost certainly have been recorded at 48 kHz, 16 bit.

When you inserted your CD recording to your VPX timeline, it would have been played back at 48 kHz. Because each second of your CD audio has only 44,100 samples per second and VPX wants 48,000 samples per second, each second your audio is, effectively, getting a little "ahead" of your video because it is taking those extra samples from the "next" second. The longer the overall playback time, the greater that difference will become.

I hope that makes sense!

I'm glad Roger's method worked for you but, personally, I would do as suggested in an earlier post, I would sample-convert the 44.1 kHz audio to 48 kHz before importing it to the VPX timeline. And I would also agree with @Michal-MST that use of an .mp3 version of the audio is best avoided!

HTH

Jeff

Thanks Jeff

The track is 5 mins long and was just over 7 seconds too short compared to the video/audio track

Yes, you are right about the sample rates and it makes sense now about how this affects the final import.

I shall try now to convert all tracks to WAV / 48000 kHz

Cheers

Bob

RogerGunkel wrote on 12/3/2018, 4:54 PM

Hi Bob,

Glad my suggestion worked and probably quicker than having to convert the files etc in this instance. However. using the same sample rates for all audio at source as suggested is the best solution for preventing a problem in the first place.

Regards,

Roger

Scenestealer wrote on 12/3/2018, 6:22 PM

Not sure on this one guys........MEP / VPX being an "open timeline" should be able to cope with different sample rates the same as it copes with different fps rates.

As Bob stated in his original post "This has never happened before and I am at a loss to fix it".

Peter

bobthevideoman wrote on 12/4/2018, 12:37 AM

Not sure on this one guys........MEP / VPX being an "open timeline" should be able to cope with different sample rates the same as it copes with different fps rates.

As Bob stated in his original post "This has never happened before and I am at a loss to fix it".

Peter

Yes, the solutions above do work, but I am now convinced that the problem is the result of the recent update. Especially as editing is now very sluggish with usually a 5 second delay between pressing any command and the action being carried out.

Thanks guys

RogerGunkel wrote on 12/4/2018, 3:45 AM

I am inclined to agree with Peter, as I have mixed sampling rates for years with no problems, although using the same at source is clearly the safest option. Having said that, most of my work is weddings, sometimes 2-3 per week and I use Sony voice recorders in mp3 for what can sometimes be a continuous ceremony up to an hour long. Apart from some slight drift over that length, I never have a problem synching sound with the occasional adjustment.

I haven't done the recent update though due to some adverse reports.

Roger