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Lossless vs M2TS

addiesin

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This thread is for anyone to post questions and hopefully for knowledgeable users to post more accurate answers than I can. This conversation started in a project thread but continuing there would be off topic so this seemed like a good place for it.

My understanding of the matter is limited, so I'm no guru on best practices, I've just picked up information and am trying to share what I understand.

Last Impressions said:
addiesin said:
Last Impressions said:
To add my 2 pennies worth. I use Clone BD which will allow you to rip a completely lossless 1:1  MP4 just for the video

I know it's confusing, but if it's an mp4, even if it is 1:1 identical quality to the Blu-ray, it's not technically lossless.

I imagine that unless we have the original master tapes or negative everything is lossy because the delivery of a file or bluray will always need to be compressed. If an unpacked MP4 file contains an MT2S  file at 25GB then surely you can only extract a 25GB file.

I think this is all correct.

Are you saying that the lagarith codec upgrades and stores/captures more pixel information and even fills in (duplicates) pixel information to enhance the picture quality and this is the reason for the larger file size. Interesting.
I am aware we are hijacking this thread with technical stuff...sorry Declan1974  :)

When you rip your disc you have a true 1:1 copy of the disc file, which was compressed to fit in the disc. If you were to convert to a lossless codec, it won't enhance anything to look better than the already compressed file but will guarantee there is no further loss in quality that comes from encoding. The benefit is avoiding generational loss from working on a compressed file, exporting a compressed "master" file with an additional layer of compression, and perhaps even converting/re-encoding that into yet another smaller file for delivery.

The file size difference comes in because the way video information is stored in compressed files takes less space but more work from software to accurately read it. Converting to lossless takes the software's guesswork away, which is why it's easier/less intensive/less error prone on editing programs, but the trade-off is huge file size.

Try saving an MP3 as a wav file, it's very similar. The new wav isn't higher quality than the mp3 you started with and is much larger, but it's also compatible with software without needing an extra codec to interpret the mp3. Another example could be a small drawing on a standard size piece of paper. You could compress that by cutting the excess paper away from around the drawing, this is not dissimilar from an official Blu-ray (at least in this metaphor). If you tape that cutout to the center of a new standard size piece of paper it doesn't add to the drawing, and yes a lot of the space send empty and wasted, but things like a printer tray, fax machine, or photocopier will only accept paper with those dimensions and shape.

I think this is more relevant if you're concerned about losing quality, or especially with standard definition edits. Personally in the age of low bitrate HD streaming, I feel that a lossless workflow with HD material doesn't benefit me and my potential audience won't notice because no matter what it'll still be better looking than a theatrical film on, for example, Netflix.

Let me know if that makes sense, and to anyone else who understands better than I, please correct me.
 

DigModiFicaTion

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I did HttF using Lossless AVI (350gb+ video file and lossless WAV audio files) and RotR in M2TS & AAC files. Every other edit I've done has taken the 1:1 source approach. I think RotR looks better than HttF and it was easier to create the edit. Perhaps I just don't have the system to notice the difference?
 

Siliconmaster

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I did my Revenge of the Sith: Rebalanced project using a direct .M2TS (straight from the Blu Ray) input through Premiere. Only converted the audio to a .ac3. It ran slow as molasses but it worked.
 

Captain Khajiit

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The discussion in the thread is mostly on the right track, though some might find clarification of the concepts and vocabulary useful.  Files on disc exist in one or more lossy delivery formats.  One converts to an intermediary (intermediate) codec for a smoother and more precise workflow: editing delivery formats is inadvisable because the manner in which the frames are stored makes such editing slow and prone to glitches, decoding errors, and imprecise cuts.  Most intermediary codecs are lossless (or near lossless) so successive renders (arising from taking clips from one to program to another to accomplish various tasks) do not lead to generational loss prior to the inevitable final encoding back to a delivery format:  they are not lossless because they attempt to improve the quality of the source files.

Years ago, we had to convert to intermediary codecs because they are what NLEs (and encoders) accepted; there was less choice, and some of the codecs were only "near lossless" (as your garden-variety file ProRes still is) and had their quirks, but we had to make the best of the situation.  Naturally, as lossless codecs became available, people gravitated toward those.  Nowadays, many NLEs import delivery formats, but if you choose to edit that way, it helps to be aware of the potential pitfalls outlined above, just as it helps to know about the TV/PC levels and color-spaces that can so easily become pitfalls when editing an intermediary codec in a given NLE; otherwise, you end up posting a "Why does my exported video look funny?" thread.

Dragging the source files into an NLE as is and cutting them up seems easier because it is easier, but it's also more limited than using an intermediary codec when it comes to precision, color-correction, compositing, effects work, etc.  For straightforward edits consisting largely of straight cuts, you might get away with the former, but there are reasons that professionals favor the latter (and spend a great deal of time acquiring the knowledge that helps them do the latter well).
 

Siliconmaster

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DigModiFicaTion said:
Do you think that was due to the file or comp specs?
 
Captain Khajiit said:
One converts to an intermediary codec for a smoother and more precise workflow: editing delivery formats is inadvisable because the manner in which the frames are stored makes such editing slow and prone to glitches, decoding errors, and imprecise cuts. 

Definitely the combination of it being a 30GB file plus it being a delivery format. I did only have 16 GB of RAM, but that was not all of the problem. I really should have converted it to an intermediate format for the basic editing process, but while it was aggravating to edit that slowly it did give me an exact representation of what I was working on. To anyone else pondering using a massive source file like that, please convert to a smaller file to do the initial editing with, it will save you some sanity.
 

Captain Khajiit

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The file-size wasn't the issue: it was the nature of the file (more than the hardware) that made it slow to edit.  Conversion to an intermediary codec would have resulted in a video that was far bigger but much easier to edit.
 

Siliconmaster

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Good to know for the future, thanks. I was worried making it even bigger would just make it worse, but it makes sense that an intermediary codec would still work better even at higher file sizes.
 

DigModiFicaTion

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Captain Khajiit said:
The file-size wasn't the issue: it was the nature of the file (more than the hardware) that made it slow to edit.  Conversion to an intermediary codec would have resulted in a video that was far bigger but much easier to edit.

Hmmm, I wonder why it seems to be the opposite for me.
 

Captain Khajiit

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DigModiFicaTion said:
Hmmm, I wonder why it seems to be the opposite for me.

That is strange.  Some codecs are faster others, but any decent (all i-frame) intermediate codec should be faster than a delivery format because it's easier to decode.  Other factors should be relatively minor.
 

Last Impressions

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. To anyone else pondering using a massive source file like that, please convert to a smaller file to do the initial editing with, it will save you some sanity
 Some NLE has the option to proxy a file. This maybe helpful when using the larger files. 16GB of RAM should not be the problem ..issues like processing speed and an inferior video card will be.
 
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