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Audio on Import yields incorrect duration

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Nemr Abou Nassar
Audio on Import yields incorrect duration
on May 24, 2010 at 10:48:36 am


I have a strange problem :S

When I import audio into my project in final cut pro 7 it imports it with a seven second difference in the duration, instead of 1:58:30:56 it is 1:58:23:00 approx and I have tried EVERYTHING.

I read in all the threads to adjust easy setup to PAL, didn't work, deleted files followed everything to the letter reimported, same result. I tried virtually easy set up with every format available to no avail.

I am saving the files originally on a windows based machine using Sony Sound Forge to master the audio track then importing it into Final Cut Pro.

I have opened the file, which I saved at 48khz 16 bit aiff, in Itunes preview and Quicktime and all display the correct duration, compressor displays the correct duration as well. Everything BUT Final Cut Pro reads the file correctly!

I tried saving the file as mp3, wav, and aiff with 48khz AND 44.1 khz setting just for the hell of it, no success :S

I am completely stumped and I am already behind on a deadline because of this, does anyone have any idea what I can do?

The fact that the duration is incorrect is causing me to be unable to have a audio track I can sync with my video track :S They should be perfectly synced and the audio just drifts in and out of sync with this.

I understand from other threads and posts this is something to do with NTSC and PAL import but like I said I tried the easy setup solution and to no avail.

My project is in PAL and my footage is all in ProRes 422 format. I tried importing footage in that and a new project all yielding same results.

I am on a mac book pro 2.86ghz 4gb ram if that helps any...

Thank you.

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Michael Gissing
Re: Audio on Import yields incorrect duration
on May 25, 2010 at 1:28:16 am

I do this almost every week. My aif file is also 16 bit 48khz from a Fairlight into ProRes 50i.

I have never had drift but I have read lots of posts that talk about drift with wav files and it usually turns out to be timecode DF or NDF or the file was imported when the easy setup was on the wrong timecode type or frame rate.

Take your aif file and load it into Compressor. As it read the duration correctly, export a new audio file with aif, 16 bit 48khz set and see if that imports into your project. Firstly make sure your easy Setup and project settings are correct.

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David Burch
Re: Audio on Import yields incorrect duration
on Aug 27, 2010 at 11:27:31 pm

I am having the exact same issue, except my audio files are 44.1k 24 bit. No matter what I try with sequence presets, the duration is always incorrect when imported into FCP. Soundtrack Pro reads the file correctly, as does the Mac OS. Any help would be appreciated.

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Kees Veling
Re: Audio on Import yields incorrect duration
on Sep 11, 2012 at 10:34:31 am

From the FCP manual:

quick fix: add the audio to a video clip in the right frame rate in quicktime 7 pro. Export as reference movie. Import into FCP. Tadaa! audio is of correct lenth

Drop Frame Indicators in Broadcast Wave Files

There is no ratified standard to indicate or detect whether a BWF file was recorded with drop frame or non-drop frame timecode. Although there are several de facto ways this information is stored, Final Cut Pro does not support reading this information. Instead, Final Cut Pro always calculates non-drop frame timecode for BWF files. You can enforce drop frame timecode during import or by using the Modify Timecode command. For more information, see Importing Broadcast Wave Files.

Mapping Audio Samples to Video Frames

Timecode is calculated for digital audio files by mapping a certain number of audio samples to each video frame. When the sample rate is an integer multiple of the video frame rate, the timecode count can be accurately mapped to the sample count. For example, if the audio sample rate is 48,000 Hz and the video rate is 25 fps, every 1920 audio samples is equivalent to one video frame.

However, with NTSC-related video rates, there is no simple relationship between the number of audio samples per second and video frames per second. To avoid ambiguity, the Society of Motion Picture and Television Engineers (SMPTE) specifies how many audio samples should be mapped to each video frame. The number of audio samples per frame is varied on a frame-by-frame basis to form a consistent pattern. Instead of an exact number of samples per frame, a consistent pattern of varying samples is spread over several frames.

When you import a BWF file, Final Cut Pro calculates timecode based on two parameters:

The editing timebase (frame rate) of the currently selected sequence preset

The audio sample rate of the imported BWF file

When the sequence preset frame rate is 29.97 fps and the sample rate of the BWF file is defined in the SMPTE specification, Final Cut Pro uses the repeating frame pattern defined in the SMPTE specification.

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