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I have shot some videos in a camcorders.
They are huge.
I used the internal feature of the camcorder (panasonic v720) to convert to MP4 and the quality was reduced very much.
What is the best practice to compress MTS videos.
What is the recommended format (avi, mp4 ?).

My targets are just to consume less disk space and upload to youtube (and have 1080p there ) with the least quality damage.
Thanks.

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2 Answers

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What is your definition of huge and what is your definition of high quality? Size is directly related to compression and compression is directly inversely related to quality for the most part.

Some amount of compression can be had for free using lossless compression or near free with more efficient pattern finding for lossy compression, but for the most part, there is a direct relationships between size and quality.

In fact, you generally have to actually increase the size to maintain the quality when re-encoding a lossy file as information that was already lost by the first can't be recovered, but other information may be lost due to the encoding process running again, so the combined error requires a higher data rate to avoid losing more.

MTS files are already generally based on H.264 (MPEG4) and are generally relatively small. It should be possible to extract the MPEG4 from the container and repackage without any loss, but to reduce size would pretty much require a reduction in quality.

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Thanks. my camera had written a few minutes of MTS file as 2 GB file. I know that this can be saved to a much smaller file (with a tiny quality compensation) since I have a few MKVs videos that hold 2 hrs 1080p/60fps on 6 GB. Excellent quality (Bluray like). Now my camera writes 6 minutes to 2 GB... –  rails Oct 23 '13 at 13:40
    
The camera you have may not be capable of capturing high enough quality to notice, but I assure you there is a huge amount of quality loss between an H.264 feed at a rate of a few MB a second vs one that is using a few MB per minute. There is even a substantial difference between a 1080p 60fps video at 2 hours in 6GB vs a bluray disk (which would take about 50 or more using the same compression). The thing is that most of that loss is covered up because it isn't the same from frame to frame, so you don't notice as much when it is playing. –  AJ Henderson Oct 23 '13 at 13:44
    
If you know what to look for though, you will see artifacts all over the place in such a lossy compression. Bluray formats (at 10 to 25 GB per hour on average are already too low for doing post production work on and then re-encoding due to the second generation loss described previously. –  AJ Henderson Oct 23 '13 at 13:47
    
If you are ok with the quality level, then the simple answer is to simply re-encode as H.264. Use any decent trans-coding application. If you are reasonably technical, you can try FFMPEG for free or you can buy a software package that will be more user friendly. To get maximum quality for the data rate you select, always choose two pass variable bit rate (2-pass VBR). This will generate the fewest artifacts and make the best use of the data rate you select, just be aware that you are in fact losing a lot shrinking it so severely. –  AJ Henderson Oct 23 '13 at 13:49
    
Do make sure that if you want to do any editing with your videos, you do it before shrinking them as they are already pretty close to as small as you can reliably work with for video editing purposes without significant second generation loss (or third as the case would be). –  AJ Henderson Oct 23 '13 at 13:51
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For YouTube you should use H.264 video format (aka AVC) in MP4 container. Full YouTube specifications you can find here

p.s. there a lot of various video converters that can do the trick

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Can you elaborate please. Do I need to convert to a *.avc file? to avi? mp4? Thanks. –  rails Oct 23 '13 at 12:44
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