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Audio Video underuns in Avid Xpress

Converting Sample Rates with Avid Xpress or Media Composer

If you are receiving any of the following error messages it is probably because you are using mismatched sample rates within you Avid Xpress project.

AdmAdm Overrun error
AMDConsumer error
Audio Underrun
Video Underrun

Audio files directly from a CD have a sample rate of 44.1. The most common sample rate used for DV media is 48k, or 32k. To keep things simple I suggest always setting your camera to record audio at the 32k sample rate. In your camera, it may give choices for 12 bit audio or 16 bit audio.

12 bit equals 32k audio
16 bit equals 48k audio

If the Avid lets you record more than 2 tracks of audio, then you know your tape has 12 bit or 32k audio recorded on it. The DV format allows you to record 4 channels of audio. It does this be reducing the quality of the audio so four tracks can be recorded on the tape. I recommend that you double deck your camera settings and always record at the 16 bit or 48k audio setting.

In Avid Xpress, an indicator of mismatched sample rates are grey waveforms (sample plots). If you see this, it is a warning that you may have problems. The sample plots should always be black, not grey.

32K_sample_plot.jpg


To avoid audio underrun problems with Avid Xpress, you need to make sure you have the following settings set up correctly. First, double click on the audio project settings within the Avid Xpress project window.

avid_audio_settings.gif

Next, set the audio project sample rate to 48K. If you have mismatched sample rates within a project, the computer may have a hard time transcoding sample rates on the fly. This causes audio under-run errors. Fortunately, the newer versions of Avid Xpress allow you to change the sample rates of audio files without having to re-import the audio files.

change_sample_rate_48k.jpg

To do this, highlight your bin, and select the audiofiles and-or media that contains the wrong sample rate.

highlight_sequences_in_bin.jpg

Next, navigate to the bin menu and select ‘change sample rate’. Change the sample rate to 48k..

change_sample_rate.jpg

choose_48k.jpg

To avoid having mismatched sample rates in the future, make sure you set the Avid Xpress software up so that it will automatically convert your imported audio files to 48k, instead of their default sample rate. This can be done within the import settings. Turn off all the options.


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Avid Express/Composer Definitions was the previous entry in this blog.

Photoshop for Video Creating Glass Bug is the next entry in this blog.

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