Need clarification on AVCHD and rendering

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offbeatbryce

Well-known member
I just upgraded my iMac to 16GB of ram and am now able to edit AVCHD natively in premiere pro CC. My iMac is an i7 quad core with 1TB fusion drive.

If I add any effects to my timeline that has AVCHD footage will the quality decrease every time I render the timeline or only on export? I keep reading that every time I render an effect it will reduce the quality unless transcoded to prores. The issue I have with pro res is the file size is larger and I don't get any quality increase because my camera only allows a maximum of 8bit color depth and the mb per second is lower than prores. I'd rather edit natively.

Thanks

Bryce
 
The reason you lose quality if you edit in/render to AVCHD from AVCHD is that it's a highly-compressed format, so you discard a lot of information. Prores is a more robust codec, so less information is lost.
 
David Jimerson said:
The reason you lose quality if you edit in/render to AVCHD from AVCHD is that it's a highly-compressed format, so you discard a lot of information. Prores is a more robust codec, so less information is lost.
Click to expand...

What happens if I do my basic editing with no effects then render and replace to prores before I add effects color correct? I don't want to transcode the whole SD card when I only need what I edited.
 
Hi Bryce,

The concept to understand is that when you render the timeline to turn red areas green, that is simply creating short temp video files on the hard drive, so that you can smoothly preview those segments from the timeline when the applied effect is too heavy to allow smooth playback. If you look under Sequence > Sequence Settings and check Preview File Format, you will see which codec that temp file is being created with.

When you go to actually Export the timeline for delivery, if you do NOT check the box that says "Use Previews", then the original source video, with effects applied, is rendered directly to the output format you are using. The temp render files are disregarded. There is no additional generational loss - you are going straight from SOURCE to DELIVERY codec, so deliverables are second generation files.

On the other hand, if you did check the Use Previews box, then for those segments that were rendered to green, the output format will be rendered from those TEMP files rather than original source clip, so there is an additional compression layer then. The deliverables would be third generation.

Now, if the preview file format is really good, like ProRes, then that may be just fine. If you had a lot of long renders, maybe you don't want to spend all that time rendering again for output. The default on the PC with older Premiere versions was always just "MPEG" and I would not use that for exporting, however I see now there are many more higher-quality options with latest CC version. Of course being on a Mac, you might have ProRes available where I do not. Also, not positive on how this works, but with *some* codecs there may be some "smart rendering" on export such that depending on source or preview format and export format, some video may be passed through basically without re-rendering. Not an expert on that, but I believe Premiere CC now offers that in certain situations.

All that said, I never render any part of the timeline - unless playback with a certain effect is too choppy for me to gauge the results of my edits. Important to know - unlike FCP, with Premiere there is no requirement that you render the timeline even if red - I often have large red areas that play back perfectly smoothly for me. When I export, it all gets rendered anyway.

Please see this Adobe blog post for good info on render bar colors and their meaning - https://blogs.adobe.com/creativecloud/red-yellow-and-green-render-bars/

Thank you

Jeff Pulera
Safe Harbor Computers
 
DigitalVision said:
Hi Bryce,

The concept to understand is that when you render the timeline to turn red areas green, that is simply creating short temp video files on the hard drive, so that you can smoothly preview those segments from the timeline when the applied effect is too heavy to allow smooth playback. If you look under Sequence > Sequence Settings and check Preview File Format, you will see which codec that temp file is being created with.

When you go to actually Export the timeline for delivery, if you do NOT check the box that says "Use Previews", then the original source video, with effects applied, is rendered directly to the output format you are using. The temp render files are disregarded. There is no additional generational loss - you are going straight from SOURCE to DELIVERY codec, so deliverables are second generation files.

On the other hand, if you did check the Use Previews box, then for those segments that were rendered to green, the output format will be rendered from those TEMP files rather than original source clip, so there is an additional compression layer then. The deliverables would be third generation.

Now, if the preview file format is really good, like ProRes, then that may be just fine. If you had a lot of long renders, maybe you don't want to spend all that time rendering again for output. The default on the PC with older Premiere versions was always just "MPEG" and I would not use that for exporting, however I see now there are many more higher-quality options with latest CC version. Of course being on a Mac, you might have ProRes available where I do not. Also, not positive on how this works, but with *some* codecs there may be some "smart rendering" on export such that depending on source or preview format and export format, some video may be passed through basically without re-rendering. Not an expert on that, but I believe Premiere CC now offers that in certain situations.

All that said, I never render any part of the timeline - unless playback with a certain effect is too choppy for me to gauge the results of my edits. Important to know - unlike FCP, with Premiere there is no requirement that you render the timeline even if red - I often have large red areas that play back perfectly smoothly for me. When I export, it all gets rendered anyway.

Please see this Adobe blog post for good info on render bar colors and their meaning - https://blogs.adobe.com/creativecloud/red-yellow-and-green-render-bars/

Thank you

Jeff Pulera
Safe Harbor Computers
Click to expand...

So you are saying if I leave the use rendered previews box unchecked it will export the timeline quality? If that's correct then why am I getting conflicting responses? I was told on another forum that you should always transcode but I don't see the point if my system is fast enough to edit avchd.
 
offbeatbryce said:
What happens if I do my basic editing with no effects then render and replace to prores before I add effects color correct? I don't want to transcode the whole SD card when I only need what I edited.
Click to expand...

You can. It wouldn't in effect be any different from transcoding before you edit, as long as you really don't add any FX before you do.
 
On what device is the output file going to be watched: youtube, dvd, pc or ........?

Rendering means making preview files to play the timeline in realtime, its non destructive. Does not matter which format is used in the timeline
Using preview files on export depends on the preview codec used in the sequence.
With avchd files as source files you do not use Preview files on export (as the preview files are of lesser quality)
If you use prores in the timeline and have the preview codec set to prores and your export is going to be prores: its ok to use the preview files.
 
Ann Bens said:
On what device is the output file going to be watched: youtube, dvd, pc or ........?

Rendering means making preview files to play the timeline in realtime, its non destructive. Does not matter which format is used in the timeline
Using preview files on export depends on the preview codec used in the sequence.
With avchd files as source files you do not use Preview files on export (as the preview files are of lesser quality)
If you use prores in the timeline and have the preview codec set to prores and your export is going to be prores: its ok to use the preview files.
Click to expand...


What about color correcting? I heard that color correcting in avchd isn't the best.
 
DigitalVision said:
All that said, I never render any part of the timeline - unless playback with a certain effect is too choppy for me to gauge the results of my edits. Important to know - unlike FCP, with Premiere there is no requirement that you render the timeline even if red - I often have large red areas that play back perfectly smoothly for me. When I export, it all gets rendered anyway.
Click to expand...

Just a note, FCP does not require you to render the timeline. You can check the box for 'background render'
on or off in the 'Final Cut Pro' > 'Preferences' > 'Playback' tab. If left off, the timeline will NOT render, but just
like Premiere, you can often play it back perfectly smoothly. I do it with my upgraded 2009 Mac Pro and
my 2013 MacBook Pro all the time.
 
alaskacameradude said:
Just a note, FCP does not require you to render the timeline. You can check the box for 'background render'
on or off in the 'Final Cut Pro' > 'Preferences' > 'Playback' tab. If left off, the timeline will NOT render, but just
like Premiere, you can often play it back perfectly smoothly. I do it with my upgraded 2009 Mac Pro and
my 2013 MacBook Pro all the time.
Click to expand...

What about color correcting? I read that you can't color correct and grade with avchd cause it creates weird artifacts etc. even if I transcode to pro res I'm not really getting a true 10 bit format because my native footage is 8 bit. So I don't understand how transcoding changes or enhances color.
 
Transcoding doesn't change the chroma data of your original, but any adjustments you make to color in the higher quality 10 bit codec will be more refined. If you want to do significant grading and avoid blocking, bleed, and banding artifacts, a DI transcode to Prores standard or HQ will definitely produce a better quality master.
 
Razz16mm said:
Transcoding doesn't change the chroma data of your original, but any adjustments you make to color in the higher quality 10 bit codec will be more refined. If you want to do significant grading and avoid blocking, bleed, and banding artifacts, a DI transcode to Prores standard or HQ will definitely produce a better quality master.
Click to expand...

So should I edit all my footage in avchd and try color correcting it? Cause I don't see any blocking etc in the timeline.
 
offbeatbryce said:
What about color correcting? I heard that color correcting in avchd isn't the best.
Click to expand...

No its not but that is all you have got and you will have to make the most of it.
No point in transcoding to another codec as you wont be adding extra info.
 
I have been very surprised at how far AVCHD can be pushed. I expected it to really fall apart. I have not done extensive color grading, but I have done pretty dramatic color correcting and color matching when things were shot waaaayyyy off white balance and even with different camera models/brands. I've also done some color work with such plugins as Magic Bullet Looks which changes the look of the footage quite a bit. And also some chroma keying (green) and was surprised there as well.

I'm not saying AVCHD is as good as those high bit rate intra frame codecs, but it isn't horrible for a lot of work.

On my 3 year old i7 PC I do not need to render the timeline. It often shows red but usually plays right on through stuff unless it's really heavy on effects.
 
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