Audacity Forum

Hi there,

Got an interesting problem to solve...

I'm in the process of recording screen capture videos which I'll then post online for my clients.

To get better sound quality, I'm using an older Digital Voice Recorder - the Olympus WS-321M.

When I try and add the WMA audio track from the Olympus to the Video that I've recorded, however, it actually ends up being a 3 seconds longer compared to the audio recorded from the onboard macbook pro microphone.

As a result the WMA audio recorded from the Olympus is out of sync with the video.

I did a bit of googling and think the problem is with the Olympus since a few others have mentioned this.

Before I go out and buy another recorder, however, is there a way in Audacity to 'compress' the audio so that it is back in sync with the video? ie. if the video goes for 45 minutes, but the Olympus WMA Audio goes for 45 minutes and 3 seconds, is there a way to squeeze the Olympus WMA audio track down to 45 minutes to match the video?

Thanks for any advice!

Adam

The problem is the format that Olympus use for recording the audio.
Have you tried opening one of the files with Audacity 1.3.12 ? (You will need to install the optional FFMPEG which is linked to on the download page: http://audacityteam.org/download/beta_mac )

Hi Steve,

I've installed Flip4Mac on my machine so I can open the WMA file directly within the screenflow software.

When I place the WMA track side by side with the audio recorded by the laptop microphone I can see the WMA track slowly getting further and further out of sync.

Further information about the WMA track:
Format: Windows Media Audio 9 Standard, Mono, 44.100kHz
Data Size: 10.6Mb
Data Rate: 32.46Kbit/s

I believe the on board microphone records at 48kHz so I've resampled the WMA file (using Audacity of course!) into 48kHz to see if that was the problem. Unfortunately, problem still remains...

Thanks for your thought though - anything else I'm missing?

Adam

Ads wrote:I can see the WMA track slowly getting further and further out of sync.

Could you be more precise about how much out of synch it is?

Video sound is 48000 sample rate. Not 44100.

Did it change at all?

Koz

The audio may not be wrong. Screen Capture software runs at the frame rate of your screen. For an LCD screen, usually around 60 FPS. Television editing (in the US) runs at 59.94. About one frame off lip sync per minute.

Koz

Hi Steve,

After much googling I've found the answer...(I'm not an audiophile so forgive the terminology if I use it incorrectly)...

Apparently the answer lies in the crystals that different devices use to time their sampling. So even if two devices are using the same indicative sampling rate, their timing may still be (slightly) out because of the different crystals...

So after much experimentation in Audacity, I found out that the audio recordings that my olympus ws321m takes need to be sped up by a factor of .298 in order to be perfectly in sync with the macbook pro in built isight microphone.

Interestingly enough, I read that others who also have the same olympus ws321m need to be sped up by a factor of anywhere between .104 and .118. You just need to find your own 'speed up' rate(!).

Once you know the 'speed up rate' of your device, you can continually use the same multiplier factor every time you use the device - so its just a pain the first time to figure out exactly what it is...

The good news is that this means that (assuming you are happy with the sound quality of a lower end voice recorder) you don't need to go out and buy a $600 Edirol since you may still run into the very same problem.

Phew!

Thanks so much for trying to chase this issue down for me.

Adam