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GoPro to AVCHD Disc?

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GoPro to AVCHD Disc?

Postby gbaldes » Mon Jul 18, 2011 9:39 am

What's the easiest, LOSSLESS way to go from a GoPro .MP4 file (1920x1080) to an AVCHD Disc? I have several video editors (Corel, Pinnacle, Nero, Sony) but I can't figure out how to burn the video onto an AVCHD disc without the software doing a transcode.

Second question: How do I combine GoPro .MP4 clips losslessly (no transcoding).

Thanks in advance for any advice. I've been looking for quite a while now...
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Re: GoPro to AVCHD Disc?

Postby Greg_E » Mon Jul 18, 2011 10:07 am

OK, you need to know a little about how the encoding works for an MPEG IPB datastream.
http://www.pinnaclesys.com/files/MainPa ... epaper.pdf

I tried to find a simple explanation but didn't want to spend too much time finding it. Essentially the B frames look at the previous and the next I frame (or P frame) to determine what they are doing. So you can not splice two separate clips together without some form of re-encoding, but the better editors will "smart" encode only the exact number of frames that are needed to get everything back on track. Exactly how you do this in the mentioned editors is something I don't know, but it should be possible with Sony Vegas to do this and output to Blueray or an mp4 files with a minimum of encoding. I know there is a re-sample option in Vegas that needs to be turned off, but I'm not sure about other settings that need to be changed. It may also be a Vegas Pro only feature, I really haven't spent that much time with it.

Now what I can say is that the paid version of VideoPad (or demo version during the demo period) will do this (or so they claim). I have made some edits that required minimal encoding and output into an mp4 file at the same bit rates as the source. They claim Blueray authoring but I never tested it and stopped using it after the demo expired moving on to other choices that currently require everything to be converted on import.
http://transportcontrols.com
Updated with version 1.
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Re: GoPro to AVCHD Disc?

Postby gbaldes » Mon Jul 18, 2011 2:56 pm

Thanks for the quick response Greg_E. I'm familiar with H.264 and MPEG algorithms in general so I'm aware of the different frame types (I P B). To simplify the issue lets stick with a single .MP4 file straight off the camera. How do I get said file onto an AVCHD DVD without re-encoding? All the software I've been using seems to want to spend lots of time processing, so I know it's not doing just a file container change (like MP4 to M2TS or the like).

I also have a Sony HDR-SR12 camcorder that produces H.264 video clips in .M2TS containers. These clips will burn to an AVCHD disc 100% unchanged with Nero editing software. Not so much with the GoPro video :) Any ideas?
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Re: GoPro to AVCHD Disc?

Postby Greg_E » Mon Jul 18, 2011 3:38 pm

They should go just the same as they are already in a Blueray standard format, but I haven't tried any disk authoring with these files, everything I have done has stayed as a file.
http://transportcontrols.com
Updated with version 1.
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Re: GoPro to AVCHD Disc?

Postby gbaldes » Wed Jul 20, 2011 2:36 pm

OK I've been doing some digging and I think I found my answer. GoPro video (R5) is 1920x1080 29.97fps progressive H.264 video and uses AAC for audio compression. Both of these are wrong for AVCHD DVD's. First off the AVCHD DVD format doesn't like AAC, only AC3 or PCM. Secondly, AVCHD DVD doesn't like 1920x1080 29.97fps progressive video; only 1920x1080 29.97fps interlaced or 1920x1080 23.976fps progressive. So as far as I can see, there's no way to go straight from the camera to an AVCHD DVD. In fact, given that the Blu-ray format is maximum 1920x1080 29.97fps interlaced also, I don't see a way to go straight from the GoPro camera to a Blu-ray disc unconverted either.

Given all this, anyone know the least intrusive way to convert a 1920x1080p stream to a 1920x1080i stream? :)
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