LAFCPUG: Audio FAQs

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Revision as of 21:23, 11 June 2008

How do I capture four (or more) tracks of audio at once?

How do I capture four (or more) tracks of audio at once?

Assuming you are capturing via Firewire...

Go to Audio Video Settings> Capture Presets

Click Edit

From the QuickTime Audio Settings > Input

You can choose to :

• Capture the First 2 channels
  
• Capture the Second 2 channels
  
• Capture mix of 4 channels
  

Mixed you can do in one pass and you still wind up with 2 audio tracks mixed down
Two pass you will have all 4 channel on separate tracks, but you would capture the First 2 normally, then change it to Second 2 channels.

Another way

From Martin Baker:
Up to 24 channel audio capture is supported in FCP5. Most capture cards support up to 8 channels of embedded audio through SDI (though Kona 3 offers up to 16 channels of embedded). I'm not aware of any capture cards which offer more than 8 AES or analogue inputs.

So depending on how many channels you want to capture, the other possibility is to use a separate audio interface such as MOTU or RME. If the interface has Core Audio drivers available then it should appear as a device in FCP's Capture Preset Editor. There may be A/V sync issues with this method although if you can genlock the audio interface then I would imagine it would work fine.

I doubt there is anyone who has ever tried this but in theory it would work.

I hear popping & clicking sounds

Q. Why do I hear popping and clicking sounds when I play my timeline?

From Jude Cotter
A. You will hear these sounds if there is a mismatch between the clip audio format and the sequence audio format. Most commonly this happens when attempting to use MP3s. The best thing to do is to convert the files to 48khz AIFFs, and import these to work with in FCP. You can do this either in iTunes or QuickTime.

• In iTunes go to iTunes > Preferences > Advanced > select the ‘Importing’ tab. Then set ‘Import Using’ to ‘AIFF Encoder’, ‘Setting’ to ‘Custom’, ‘Sample Rate’ to 48.000kHz, ‘Sample Size’ to ‘16 bit’ and ‘Channels’ to ‘Stereo’. Find your tracks in the iTunes Library and select ‘Convert’ from the ‘Advanced’ menu.
  

This option is best if you need to batch convert a lot of songs.

• In QuickTime, open the file and choose File > Export. Change the ‘Export’ setting at the bottom of the window to ‘Sound to AIFF’. Click on ‘Options’ and check that the settings are correct. Then save to the location of your choice.

Other things that could help:

• Before you output your sequence to a movie file or to tape, you must perform an Audio Mixdown. This does not mix all your audio tracks to two tracks; it merely serves as an audio render for the entire timeline - it creates a single preview file that is less stressful for the computer to play. You can find this in FCP under Render > Only > Mixdown.

Imported songs from a CD

Q. I imported some songs from a CD and it worked at first, but now the files are missing and won't play.

From Jude Cotter
A. If you import audio files directly from a CD, FCP (on OSX) does not automatically create a file on your hard drive - instead, it makes a "dependent" or "reference" clip to the CD.

This means that once you eject the CD, FCP no longer has access to the audio file. To ensure that you always have access to the file for use in FCP, you must convert any CD tracks to AIFFs and store them in your computer before importing them into FCP.

To do this:

• In iTunes go to iTunes > Preferences > Advanced > select the ‘Importing’ tab. Then set ‘Import Using’ to ‘AIFF Encoder’, ‘Setting’ to ‘Custom’, ‘Sample Rate’ to 48.000kHz, ‘Sample Size’ to ‘16 bit’ and ‘Channels’ to ‘Stereo’.
  
• Find your tracks on the CD and select ‘Convert’ from the ‘Advanced’ menu.
  

This option is best if you need to batch convert a lot of songs.

• In QuickTime, open the file and choose File > Export. Change the ‘Export’ setting at the bottom of the window to ‘Sound to AIFF’. Click on ‘Options’ and check that the settings are correct. Then save to the location of your choice.

Then import the files you have created into FCP.

Other things that it could be:

• If you did all this before importing the files and they‘ve still gone missing, it could be that the name of the files has been changed on the hard drive, so that FCP no longer recognises them as the correct files. Either change the names of the files back to what they were, or reconnect them in FCP by deselecting ‘Matched name only’ in the reconnect dialogue box.

Why do I hear beeping?

Q. Why do I hear a beeping sound when I play my timeline?

From Jude Cotter
A. The beeping noise is the audio render alert. It means that you need to render your audio. A normal render should do this, as long as you have ‘Audio’ checked under Sequence > ‘Render Selection’ and/or ‘Render All’.

From Nick Meyer
B. Increase your Real Time Audio Mixing track allocation in User Preferences to perhaps 16 tracks rather than the default 8.

Some sections of my audio are missing or sputtering

Q. Random sections of my audio appear to be missing. The project used to be fine and now it's getting worse.

From Jude Cotter

• Your computer has reached the limit of what it is able to display in real time. You may find that your video also starts to splutter after a while. What you need to do is to reduce the pressure on the system by doing an 'Audio Mixdown'. This creates a single stereo preview file for FCP to play when you watch your timeline. This is not the same as an audio render.

Doing this does not actually mix all your audio together - all your audio is still separated exactly as you have designed it to be - there is just a single extra file that represents what audio decisions you have made. If you change anything in the audio, you will need to do the Audio mixdown again. Fortunately, this is quite quick.

To do an audio mixdown, go to Render > Only > Audio Mixdown.

Other things that it could be:

• Your audio is actually missing. Check your original files and tapes.
• You have accidentally turned off or deleted a part of your audio. Check that everything appears normal on the timeline.

If the Audio mixdown starts to become too tedious:
You need to reduce the pressure on your system further (or get more RAM, a bigger computer etc). Try exporting sections of your work that are locked-off to self contained Quicktime movies and re-importing them to use in place of the more complicated parts of your timeline.

I'm having sync problems

Q. My sound sync is fine if I just play the tape or watch my clips in QuickTime Player, but the sync is off by a few frames if I'm watching the clips in the FCP viewer or timeline.

From Jude Cotter
A. If you're playing back to an external monitor, you must also listen to the sound with an external playback device. If you're watching the image on the Viewer or Canvas, then you must listen to the sound on the computer's Built-In Audio option under Audio/Video Settings, or by turning View - External Video off (at which point Built-In Audio will kick in). If you're watching external video, for example FireWire from the computer to a deck to a monitor/TV, then you must monitor sound from the deck or the monitor/TV.

Other things that it could be:

• Have you accidentally slipped the sync in the timeline? Check the original clip against the version on the timeline. You may see a small set of red numbers on the out of sync clips. This number is a guide to how far off sync you have moved. To fix this, right click or control-click an out-of-sync indicator to reveal a shortcut menu with several options.

‘Move into Sync’ moves the selected track so that its In point syncs with that of the associated track. Make sure you have enough room on the timeline for the track to move into.

You can also just select the out of sync clip and type the number indicated in the red boxes. Make sure to add a minus if you need the clip to move backwards.

More help/solutions can be found here:

Dropped Frames: Causes and Solutions

No audio from movie file (MPEG) after I import

Q. I don't get audio from a movie file I just imported into FCP. I can hear the audio if I play it in QuickTime Player, but there's no sound when I play the file in FCP. Why?

From Jude Cotter
A. MPEG-1 and some other compressed codecs use ‘muxed’ or ‘multiplexed’ audio, which means that the audio is mixed in with the video. FCP does not like this.
To check for muxing, open the clip in QuickTime Player and press APPLE-J. Check the Sound Track. If you see the words "Muxed Track", the clip needs to be 'demuxed' before it can be used for editing.

You can do this with MPEGStreamclip

Other things that it could be

• If you have external speakers, check that these are turned on and set up correctly. Make sure your mixer, if any, is on and that everything is securely connected.
  
• Try restarting FCP.
  
• If all else fails, try trashing your preferences to restore the factory settings. Instructions on how to do this can be found here.
  

How to trash your preferences

Or you can use Preference Manager a highly recommended and free utility from Digital Rebellion.