I've read everything that I think has been written on the subject in the manual, Adobe forums, Creative Cow, etc. etc. Some say they don't even bother with preview files because they are plagued with "issues." Some of these issues are they sometimes magically disappear. Others say they speed up exports, others say they don't. So the jury was out with nothing conclusive.
Well, I have been testing and testing for the last 30 hours to try to streamline my exports that are taking way too long. (2 hours for a 9 minute clip. See this other thread http://forums.adobe.com/thread/882985?tstart=0)
So, in search to find a solution to my slow renders, I have tested this and retested this using many different scenarios. My real-world tests CONCLUSIVELY show that Previews are WORTHLESS for exports. They certainly can help you scrub through a slow timeline, but that's where their usefulness ends.
I rendered out the same 7 minute section of a TV program with the following details.
- This particular section isn't overly complicated in either audio or video.
- I have disabled all dynamic links to AE and replaced them with either a DNxHD encoded clip or a TIFF sequence
- 90% of the footage is from the Sony EX1r camera, the other 10% from the Canon 7D or 5Dm2.
- I rendered out the entire sequence (turned the entire timeline green)
- The sequence is set up to process its renders with Microsoft AVI / Cineform codec, highest resolution settings, 1920x1080p, square pixels.
- I exported the same sequence many different ways. One was doing it like everyone does by exporting your sequence timeline as normal (with all your cuts, etc.). The other way was using THAT export, exported as Cineform .AVI, and dropping THAT .AVI into a new sequence and rendering the .AVI instead of all the cuts. The clips were of the exact same thing, just one was an export of a "real" timeline, and the other was an exported version of that same timeline. I used the following settings with the following export times according to AME logs:
- EXPORTED 7-MINUTE TIMELINE
- 21:54 - Matching sequence settings using previews
- 22:26 - Matching sequence settings not using previews
- 23:03 - Cineform .AVI (not using "Match sequence") with previews
- 23:50 - Cineform .AVI (not using "Match sequence") not using previews
- 21:44 - H.264 Target 15.72, Max 18.61 Mbps using previews
- 22:33 - H.264 Target 15.72, Max 18.61 Mbps not using previews
- CINEFORM .AVI COPY OF TIMELINE
- 3:31 - Matching sequence settings using previews
- 3:39 - Matching sequence settings not using previews
- 3:36- Cineform .AVI (not using "Match sequence") with previews
- 3:39 - Cineform .AVI (not using "Match sequence") not using previews
- 7:07 - H.264 Target 15.72, Max 18.61 Mbps using previews
- 6:58 - H.264 Target 15.72, Max 18.61 Mbps not using previews
To top it all off, I did another test where I took just one long, unedited clip from the Sony EX1. I exported it several different ways to Cineform .AVI.
- 8:00 - to export straight from timeline
- 7:50 - to export using previews
- 1:55 - to re-export using the .AVI made from one of the above
- 1:21 - to export (without audio) the actual preview file made by Premiere (located in the Preview folder)
This clearly shows that "use previews" does absolutely nothing when you export. If it WAS using the preview files (which I have set up as Cineform .AVIs), you would expect to see render times very close to what it takes to render the actual Cineform .AVI exports since that's exactly what the preview files are supposed to be. My testing shows the preview files are being used VERY little, if at all in the final export.
You clearly see that using previews saves just a nominal amount of time off of exports--just seconds. When considering this time difference could be influenced by other factors (e.g. other Windows processes running), the difference between using previews and not is non-existent. Moreover, when you factor in the time you had to take to actually MAKE the rendered preview in the first place, you are far behind using them (other than for more fluid playback).
Someone from Adobe, I think Jeff, told me to test my results. Well, here they are and they are very disappointing.
If someone can find a flaw here, let me know. My post isn't to make Premiere look bad (although this data does), but to make my renders faster. And clearly using preview files isn't part of that solution--at least using Cineform as a codec.