Exporting an already compressed video

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Level 1

11 points

Exporting an already compressed video

Hey guys,

This is the scenario... I have a capture card that records my gameplay from my PS3. It captures in uncompressed video which is pretty much 1GB every 10 seconds for 720p. To preserve hard drive space, I always convert my captured gameplay (that is usually about 10 mins long, which is just over 60GB) to H.264 720p using Wondershare Video Converter Pro. So basically I have my video perfect in size and quality and now just want to record some commentary over the top of my gameplay.

Is it possible to import the already compressed video file into iMovie, record a voiceover and attach that audio that I've just recorded to the video without re-compressing? Basically I don't want to lose any quality through the export process. Anyone know what I mean?

Here's also what I want to know... If I export a movie from iMovie... So I go to Share -> Export Movie and choose HD 720p... And then create a new project, import that movie that I just exported and export it the exact same way again, will there be any quality lost? I tried doing some tests but it's hard to tell...

Thanks for reading. Any input appreciated.

Regards,

Daniel

Mac Pro 3.2GHz Quad-Core Intel Xeon "Nehalem" (Mid 2010), Mac OS X (10.6.4), 12GB 1066MHz DDR3 SDRAM

Posted on Jan 29, 2011 6:14 AM

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Answer 1

Best reply

AppleMan1958

Level 7

27,492 points

Jan 29, 2011 6:22 AM in response to IlMolto

iMovie will recompress.
If you cannot tell the difference, then keep doing what you are doing.

For a slightly better workflow, convert your uncompressed video to Apple Intermediate Codec. This will be much smaller than uncompressed but 4 to 10 times larger than h.264. Then when you export to h.264, you will have more to work with and get better performance.

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Answer 2

IlMolto Author

Level 1

11 points

Jan 29, 2011 10:09 AM in response to AppleMan1958

Interesting. I will keep that in mind. Thanks for the info.

I did some more tests regarding the exporting an already exported video and it seems there is some loss of quality, mainly in the colour. It appears brighter and more washed out if you know what I mean. I guess the less times you compress, the better.

Thanks again, AppleMan 🙂

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Answer 3

IlMolto Author

Level 1

11 points

Feb 1, 2011 8:21 PM in response to AppleMan1958

Hi again AppleMan,

When optimizing a video, will iMovie use the optimized video when exporting, or the original? I feel iMovie runs a lot better when the video is optimized. It scrubs better and plays the video nice and smooth, even when creating a picture-in-picture effect. The question is though, what does it refer to when exporting? As you know, the original files are uncompressed 8-bit YUV. There's a lot more in these files than the Apple Intermediate Codec (which still has a lot in them), but would obviously rather export using the bit rate in the uncompressed files.

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