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Old February 1st, 2010, 04:29 PM   #1
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Join Date: Mar 2005
Location: Portland, Oregon
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m4v, quicktime and VLC gamma question

I'm wondering if someone could help me check my work flow.

I have to deliver a m4v file to a client.

720 30p HDV project. Right now I'm rendering out as uncompressed .avi from Vegas with the studio rgb to computer rgb gamma preset added. Then rendering to a m4v web file in Quicktime pro. Everything is working fine but I'm getting different gamma/audio sync results depending on the player.

If I play the file in quicktime, which will be the default player for most I'm guessing, the gamma looks correct but the audio sync looks a little off.

If I play back in VLC the gamma looks too dark but the audio is right on.

Should I not be adding the studio rgb to computer rgb preset to my uncompressed render? In my testing this made the file look to washed out when played in the quicktime player but right on the money in VLC.

Which player should I trust here? Any info on the sync issue?

Any help much appreciated!
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Old February 9th, 2010, 05:07 PM   #2
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Join Date: Jun 2004
Location: Northern Virginia, USA
Posts: 34

Quicktime is right, with the RGB conversion, VLC is wrong.

As for the audio sync, I couldn't tell you one way or another, but I always use MEGUI to produce my .mp4 deliveries. (.m4v is basically the same container format.)

Here is some background on the studio/computer rgb issue in vegas, it is not a simple matter:
Color spaces and levels in Sony Vegas 9

Basically, you should only add the studio to computer rgb on your individual events, if it's needed. As it really depends on what levels your output codec is expecting and how vegas is going to treat your event (for example -- Vegas keeps the studioRGB for AVCHD, which makes the preview window wrong).

My workflow is this: Make sure everything on the timeline is computerRGB (this makes the preview window correct), output to losslessly compressed Lagarith, which expects computerRGB levels. Convert to mp4 with megui.

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