Wrappers transcoders codecs headers

-Tom-

-Tom-

Active member
Please someone point me to a tutorial explaining these things. I grew up on "codecs" (avi, mpeg, qt...) but apparently I didn't keep up with the times..now I'm experimenting with Resolve Lite and apparently I need to convert the headers of my MTS file to ProRes - wrap the clip in a new container so Davinci could read it.

I'm lost - please help :D I come from web background, I still confuse web XML (sitemaps) and video editing XML :D
 
Well . . .

AVI and QT aren't codecs, they're wrappers -- containers. The video they contain can be of many codecs.

MTS is a format carrying the AVCHD codec, while ProRes is a codec which needs to be carried in a container -- they are not at all the same thing, so you can't just change the header, or rewrap it. You need to transcode it, and for that, you need transcoding software or other software (like an NLE) which can do it.
 
OK, fair, I get it and I've just read up on wrappers and codecs. Now my question is a bit more specific. My camera (GH2) give me MTS files. The top of the camera read AVCHD. I guess MTS is wrapped into AVCHD?

What do I exactly, technically do to the file (MTS?) when I pass it thru 5D2RGB (im doing that now, for Resolve). I managed to get my MTS files into Resolve by converting (transcoding?) them to H264 via Adobe Media Encoder.

Don't I crush the file quality by doing so? If I need to take MTS originals from the camera to Premiere to cut, then export to 264 for Resolve, I already did 2 convertion to the file, add in Vimeo/YouTube compression...

Or am I talking the wrong way altogether :D
 
No, AVCHD (the codec) is wrapped into MTS (the format).

AVCHD and H.264 are pretty much the same thing (they are variants on the same codec, along with MP4), so you may not have lost any generations or recompressed at all.

What exactly did you do in Adobe Media Encoder?
 
I just encoded the MTS file to H.264 and I was able to put it into DaVinci timeline (by the way, I'm impressed by the elegancy of that program, if I somehow manage to figure out the workflow I'm ready to go full in, I'm literally blown away by some stuff that piece of software can do...)

Now I just finished with my first 5D 2 RGB conversion (APR 422, 709, Full Range)...it converted my 2 GB MTS file (17 minutes RT, 720p 60fps) into a 20 GB MOV.

I can't open the MOV file in Media Player Classic HC, but I can open it in Quick Time. It looks somewhat worse than the original, first thing I've noticed is the red borders in the footage are bleeding. In the original file, opened in MPC-HC (with "video mixing rendered 9", if that makes any difference) the red borders look just fine.

On the other hand, it appears to me that the shadows in the ProRes file are not as crushed as in the original MTS.

What did the 5D to RGB do to the MTS, it's 10x the size but the quality is down a notch...am I supposed to lose info within my pixels like this, or is there a safer workflow?
 
you have to think to codecs as root of signal. But video is more than one signal, usually it contains picture, sound, subtitles and possibly several streams of each.
so that is why you got container like AVI or quicktime (on computers) but also the ones created for cameras (like XDCAM).
Container are not there to describe what is in the box, but more how it is arranged , so the different parts of the contents can be played properly. That's why an AVI file can contain almost anything.
The difference between Wrappers and Containers is subtle, but think Wrappers as not changing content at all (so you can transform an AVI into Quicktime without recompiling the file or even reading it.) . Usually Wrappers are used for application to enforce particular specification. I suspect most companies are using wrappers to pretend to own a format, while usually content is all the same.
Most camera today use AVCHD, but you can hardly interchange them from one camera to another one because different wrapping.
to make thing even more fuzzy, some codecs have enough feature to look like container (like mpeg).
for example, most Mpeg (2 and 4) can implement several combination of audio codecs along with video codec, So from that point of view, AVCHD looks more like a container than a codec.
For example, mpeg2 can exist under different form, depending if it is for recording or for transport. historically, mpeg2 was known under it simple form, until sony and JVC invented HDV. HDV was tweaking a special form intended for transmission ( .TS = Transport Stream)) as recording format. Since it has been a common practice.
Transport codec are a bit different than usual codecs because they introduce 2 additional features. They are clocked and lossy.
These 2 features are necessary to make the stream fault tolerant, so even if there is some bump on the path between the satellite and your dish antenna, you would still be able to enjoy the show.
 
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Think of it like a bunch of jpg or png images inside a zip file or a rar file.

Zip/Rar is the container/wrapper/format, jpg/png is the codec

The header would be a block of information at the start of the container describing what kind of container it is, what kind of codecs are within it, where the video files are stored, where the audio files are stored, etc.. It can be thought of like a foreword and table of contents in a book.

A transcoder is a piece of software that would translate the video/audio from one codec to another, but it doesn't necessarily need to change the container.
 
Thanks for these answers guys!...now I need to figure out what did ProRes conversion did for me :D
 
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