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-   -   Is AVCHD lossy when editing? (https://www.dvinfo.net/forum/avchd-format-discussion/238960-avchd-lossy-when-editing.html)

Paul Cascio July 13th, 2009 09:23 AM

Is AVCHD lossy when editing?
 
I would think it is very lossy, but I'm not sure. If this is so, why should we edit AVCHD without transcoding, assuming you're doing more than simple cuts?

Perrone Ford July 13th, 2009 10:24 AM

Quote:

Originally Posted by Paul Cascio (Post 1171151)
I would think it is very lossy, but I'm not sure. If this is so, why should we edit AVCHD without transcoding, assuming you're doing more than simple cuts?

Yes it is lossy. Not sure why you'd edit it on the timeline. I certainly wouldn't.

Paul Cascio July 13th, 2009 11:42 AM

Thanks Perrone - so much attention has been focused on the hardware need to cruch AVCHD, but even if you can edit it, there's no reason usually to want to without transcoding.

Perrone Ford July 13th, 2009 12:06 PM

People do a great many things that mystify me. You read stuff every day about people beating their head against walls and I just wonder why. The more I read about the offline/online workflow for film, the more it made sense to me.

Cutting SD sized video on todays machines even with multiple layers, color corrections, etc. is an absolute breeze. Why on earth would I want to spend big money just so I can edit native uncompressed 1080 on the timeline? I can see rendering portions for color check and other things, but especially for just editorial, who needs HD?

I'd MUCH rather cut in SD at 5 times the speed, do a basic color grade, lock the audio, etc., then conform my footage.

I have worked with cutting HD on the timeline in Cineform, DNxHD, and even Jpeg2000. In the end, I was never happy with any of them for cutting. I have a new octo core PC with a lot of RAM and one of the hottest graphics cards around, but I'll still cut SD most likely.

Cris Hendrix July 13th, 2009 01:54 PM

Well personally I'm making a low budget movie and SD simply doesn't look that great on a 52" lcd hd screen which is what I use as a testing source. I can't understand editing AVCHD natively when Cineform, Voltaic, CoreAVC, etc.. are available. Convert it to an hd avi or intermediate format and you can edit it on pretty much any editor you want on a moderately powered machine

Perrone Ford July 13th, 2009 02:18 PM

Quote:

Originally Posted by Cris Hendrix (Post 1171286)
Well personally I'm making a low budget movie and SD simply doesn't look that great on a 52" lcd hd screen which is what I use as a testing source. I can't understand editing AVCHD natively when Cineform, Voltaic, CoreAVC, etc.. are available. Convert it to an hd avi or intermediate format and you can edit it on pretty much any editor you want on a moderately powered machine

I think you missed my point. But maybe your editing workflow is different than mine. Here's what I do on long form projects.

1. Copy all media into a folder called project\HD
2. Open NLE and place all that media on the timeline
3. Save that project file
4. Render that timeline to HD in best format available (best codec)
5. Render that timeline to SD file
6. Start edit on the SD file. All cuts, transitions, audio, etc are done here.
7. Once everything is a lock, conform the HD version. There are a number of ways to do this. In Vegas, it's as easy as changing the name of the SD file to temp, and then naming the HD file what the SD one was named. Now you have a full HD copy with all your edits.
8. Do color correction and grading, titles, etc.
9. Render final.

This can be more tricky for multi-scene projects, but I just did a 6 month long project using HD intermediate (DNxHD 36) and will work in SD next time.

Everyone has preferences and a different way of working. So if this doesn't work for you, no biggie. Just think about what you need to do, and get it done... :)

Brian Boyko July 13th, 2009 03:23 PM

AVCHD is lossy, yes, but editing it on the timeline shouldn't introduce <i>more</i> loss. (Compared to transcoding to an intermediate format.)

Where you introduce additional loss is by rendering out to AVCHD and then re-inputting that output back into the footage - for things like compositing effects. Then, I render out to Cineform for those particular cuts, but the majority of my timeline is still AVCHD.

I know everyone talks about how you need a super-fast computer to render AVCHD, and that may be true, but have you priced super-fast computers lately? You can build a quad-core for less than $800, probably even less if you cannibalize your old system.

Brian Boyko July 13th, 2009 03:24 PM

Quote:

Originally Posted by Perrone Ford (Post 1171291)
I think you missed my point. But maybe your editing workflow is different than mine. Here's what I do on long form projects.

1. Copy all media into a folder called project\HD
2. Open NLE and place all that media on the timeline
3. Save that project file
4. Render that timeline to HD in best format available (best codec)
5. Render that timeline to SD file
6. Start edit on the SD file. All cuts, transitions, audio, etc are done here.
7. Once everything is a lock, conform the HD version. There are a number of ways to do this. In Vegas, it's as easy as changing the name of the SD file to temp, and then naming the HD file what the SD one was named. Now you have a full HD copy with all your edits.
8. Do color correction and grading, titles, etc.
9. Render final.

This can be more tricky for multi-scene projects, but I just did a 6 month long project using HD intermediate (DNxHD 36) and will work in SD next time.

Everyone has preferences and a different way of working. So if this doesn't work for you, no biggie. Just think about what you need to do, and get it done... :)

Ooh, this is AWESOME. I'm going to try that next project!

Tripp Woelfel July 13th, 2009 06:37 PM

Quote:

Originally Posted by Perrone Ford (Post 1171174)
Not sure why you'd edit it on the timeline.

If you're doing cuts only with no color correction there will be virtually no loss in quality with AVCHD if you go from there to a lossless or the final delivery codec. Now, different NLEs might or might not make a hash of things doing this but Premier Pro does not. I put AVCHD on timelines all the time using the guidelines I stated above with great results.

That said, if you're using transitions, effect and color correction an intermediate codec is preferable as any highly compressed codec in a 4:2:0 color space (which I think is what AVCHD is) can quickly end up looking like the dog's dinner.

Cris Hendrix July 13th, 2009 09:19 PM

Quote:

Originally Posted by Perrone Ford (Post 1171291)
I think you missed my point. But maybe your editing workflow is different than mine. Here's what I do on long form projects.

1. Copy all media into a folder called project\HD
2. Open NLE and place all that media on the timeline
3. Save that project file
4. Render that timeline to HD in best format available (best codec)
5. Render that timeline to SD file
6. Start edit on the SD file. All cuts, transitions, audio, etc are done here.
7. Once everything is a lock, conform the HD version. There are a number of ways to do this. In Vegas, it's as easy as changing the name of the SD file to temp, and then naming the HD file what the SD one was named. Now you have a full HD copy with all your edits.
8. Do color correction and grading, titles, etc.
9. Render final.

This can be more tricky for multi-scene projects, but I just did a 6 month long project using HD intermediate (DNxHD 36) and will work in SD next time.

Everyone has preferences and a different way of working. So if this doesn't work for you, no biggie. Just think about what you need to do, and get it done... :)

No problem I didn't know you were talking about using intermediates or proxies I thought you were actually outputting in SD

Noa Put July 14th, 2009 05:44 AM

Quote:

Originally Posted by Perrone Ford (Post 1171291)
Just think about what you need to do, and get it done... :)

That's the first time I hear about this way of working and you got me really interested. So if I understand you right when you start editing on the sd file, you are doing this from within the HD project file?
I tried the workflow as you described in premiere cs3 by creating a hdv project file, the only "problem" I saw was that the sd file was a lot smaller in the preview window as it was expecting a 1440x1080 file so I had to magnify it a bit.
Renaming the HD file back to SD file name also worked without a problem in CS3 as it would immediately ask were the "missing" file was and conform it again.

Also is there a reason why you color correct after you conformed to the hd file, is that not something you can do on the sd file as well?

The reason why this interests me is that I"m using a sony hvr-dr60 ext harddrive and can end up to 200-300 small MT2 files that I need to drag in my project file in their native size. If I'm scrolling the timeline Premiere and my int harddrive have a hard time keeping up as it needs to access all those files almost instantly to give me a live preview. Rendering it into a big HD file and editing it in one big SD file would mean that premiere only needs to read from one SD file on my int drive and that would be real easy. Another problem I have is that Premiere takes ages opening a project when it has over 200 small files in it, your workflow also means I could remove the 200-300 small files from the project after I have rendered to a large HD and SD file, right? That would be a big timesaver.

Perrone Ford July 14th, 2009 06:35 AM

I think you are missing something. Let's say I am about to begin a project. I create my folders:

\Project
\Project\source files (where I keep the original clips, HD big file and SD big file)
\Project\asset files (any audio or other stuff to add)

I open the editor, drag everything onto the HD timeline that I intend to use and render HD_timeline.mov or HD_timeline.avi.

I then change the project settings to SD size and re-render the exact same timeline to working_project.avi.

I then begin editing the SD version. All cuts, transitions, audio, a basic color grade, etc. are done here. Then I save the file. Exit the editor.

Rename working_project.avi to sd_timeline.avi. Rename HD_Timeline.avi to working_project.avi then reopen the editor. I am now looking at an HD version of my project with all cuts, transitions, color grade, and audio. It is a frame-for-frame copy of what I have been working on.

Now I just do my basic tweaks of color, add titles, and do my final renders.


Ok?

Quote:

Originally Posted by Noa Put (Post 1171543)
That's the first time I hear about this way of working and you got me really interested. So if I understand you right when you start editing on the sd file, you are doing this from within the HD project file?
I tried the workflow as you described in premiere cs3 by creating a hdv project file, the only "problem" I saw was that the sd file was a lot smaller in the preview window as it was expecting a 1440x1080 file so I had to magnify it a bit.
Renaming the HD file back to SD file name also worked without a problem in CS3 as it would immediately ask were the "missing" file was and conform it again.

Also is there a reason why you color correct after you conformed to the hd file, is that not something you can do on the sd file as well?

The reason why this interests me is that I"m using a sony hvr-dr60 ext harddrive and can end up to 200-300 small MT2 files that I need to drag in my project file in their native size. If I'm scrolling the timeline Premiere and my int harddrive have a hard time keeping up as it needs to access all those files almost instantly to give me a live preview. Rendering it into a big HD file and editing it in one big SD file would mean that premiere only needs to read from one SD file on my int drive and that would be real easy. Another problem I have is that Premiere takes ages opening a project when it has over 200 small files in it, your workflow also means I could remove the 200-300 small files from the project after I have rendered to a large HD and SD file, right? That would be a big timesaver.


Noa Put July 14th, 2009 07:09 AM

Thanks Perrone for your time to explain this, problem with premiere is that you can't change the project settings anymore once it has been set, once saved all project settings are light grey and not possible to change. guess that Vegas can handle this in a different way.

You said that when you are done editing the sd file you save and close the editor. After you renamed the files and reopen that same project, does vegas then automaticly set the project setting from SD back to HD?

Since I"m not able to change these settings I guess the workflow I described for Premiere would be the only way to deal with this, not ideal but still not bad, maybe it's time to change to Vegas :)

Robert Young July 15th, 2009 01:22 AM

Quote:

Originally Posted by Noa Put (Post 1171566)
Since I"m not able to change these settings I guess the workflow I described for Premiere would be the only way to deal with this, not ideal but still not bad, maybe it's time to change to Vegas :)

To use this workflow in Premiere CS3 try this:
1) save your finished SD proxy project
2) rename the large HD & SD files as described
3) open a new project in CS3 with the appropriate HD settings- name it "Final HD Edit", etc.
4) import the SD proxy project into the new HD project, double click it & it should open up on an HD timeline using the large HD file to give you the final edited project in HD.

Kevin Zibart July 15th, 2009 12:21 PM

What about panning, cropping and track motion? Does Vegas Pro reapply those correctly to the HD file even though they were originally created against an SD file? In Vegas Movie Studio, it appears to represent everything as absolute values relative to the source video's resolution. So I wouldn't think they would be applied correctly if the underlying source video's size changed.


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