13 Replies Latest reply: May 28, 2014 7:25 PM by Nanda_KP RSS

    Use Previews - to use them or not for final export

    Nanda_KP Community Member

      First off, I have read through the forum hits typing 'Use Previews' and clicking Ask Now.

      I've read an article by Todd Kopriva that says it is NOT recommended to use previews for final export stating it can result in lower quality final output

      I've read this thread, which says the same thing: "does using "use previews" button is recommended?ended"

       

      I'm a little confused.

       

      I have Neat Video and RGB curves effects applied to AVCHD footage - and this shows a red bar on the time line. I obviously can't playback in real time.

      So what I've chosen is

      - Render Effects in Work Area, on all the clips, with not modifying the Sequence settings, i.e with using full resolution etc.

      - export the timeline with checking Use Previews

       

      since my previews are rendered using same resolution as source, using them in Export, should result in no loss of resolution, as per my understanding. Is that correct?

       

      I am applying those effects to 3 camera angles spanning about 3 hours (sorry, I know) and I wanted to do a multicam sequence final output.

       

      So I thought about these 2 approaches:

       

      approach 1:

      - tune the effects on the clips to my satisfaction

      - disable them on source timeline (resulting in green/no render bar which will allow me to playback in RT without issues)

      - create multicam sequence from them

      - go to each clip in multicam sequence and re-enable the effects and then kick off the Export on the multicam sequence

       

      approach 2:

      - tune the effects on the clips to my satisfaction on each clip and render them using full resolution and frame size (to allow RT playback in multicam sequence)

      - create multicam sequence from the clips

      - then kick off the Export on the multicam sequence

       

      With both approaches, I ran into issues with CS6, in that after I closed the project and reopened it, PPro lost link to the render files - as a result the timelines went back to red and there is no way I can re-link the preview files.

      (I posted this on the forum here)

       

      so, I came up with approach 3:

      - tune the effects on the clips to my satisfaction on each clip and render them using full resolution and frame size (to allow RT playback in multicam sequence)

      - export each clip using source settings.

      - reimport the final clips into new sequence and then create a multicam sequence from them

      - then kick off the Export on the multicam sequence

       

      When I play the preview files, obviously I don't see any loss in quality even at full screen, since I rendered them without modifying the sequence settings.

       

      So, my conclusion is that using previews for Export is not recommended IF the previews were creating using either lesser resolution or bit depth than the source.

       

      Appreciate anyone confirming my thoughts about or correcting them.

        • 1. Re: Use Previews - to use them or not for final export
          Nanda_KP Community Member

          Small correction:

           

          so, I came up with approach 3:

          - tune the effects on the clips to my satisfaction on each clip and render them using full resolution and frame size (to allow RT playback in multicam sequence)

          - export each clip using source settings with selecting Use Previews

          - reimport the final clips into new sequence and then create a multicam sequence from them

          - then kick off the Export on the multicam sequence

          • 3. Re: Use Previews - to use them or not for final export
            Richard M Knight Community Member

            Although the bit depth and resolution of the preview files will be the same as your sequence in most cases the codec used will not be lossless. Some sequence types will let you change the codec to a 'better' one but the ones I use for Sony Excam are fixed as I-frame only Mpeg.

            • 4. Re: Use Previews - to use them or not for final export
              Ann Bens CommunityMVP

              If the preview codec is I-frame only Mpeg then dont use the previews as they are of lower quality and dont use match sequence settings.

               

              Neat Video is not GPU supported hence the red bar.

              • 5. Re: Use Previews - to use them or not for final export
                Nanda_KP Community Member

                @Richard, @Ann, other members

                 

                Thank you for your responses.

                 

                I looked further based on your comments:

                 

                source clip 1

                - is from Matrox capture

                - it is 8-bit 4:2:2 MPEG-2 I-Frame HD

                - overall bitrate is 100Mbps

                - 1920x1080 frame size

                -

                 

                source clips 2

                - is AVCHD (.mts)

                - format is Advanced Video Codec (BDAV)

                - overall bitrate is 273 Mbps (I doubt this from MEdiainfo)

                - maximum overall bit rate is 18Mbps

                - 1920x1080 frame size

                - 8-bit

                 

                source clip 3

                - is AVCHD (.mts)

                - format is Advanced Video Codec (BDAV)

                - overall bitrate is 12Mbps

                - maximum overall bit rate is 18Mbps

                - 1440x1080 frame size

                - 8-bit

                 

                When I examined the rendered previews for all the above clips (I rendered each clip on different days, so I could determine which previews belonged to which clips) using MediaInfo

                - they all show up as M701 codec files (Matrox AVI) with 1920x1080 size.

                - The writing application for all previews is Matrox DSX AVI file.

                - overall Bit rate for all of them is ~100Mbps.

                 

                I did not change any sequence settings for any of the clips before doing Render Effects In W

                 

                So, again I am not so sure that using previews in this case for final export would lead to lower quality output... please let me know if you agree with my thoughts or have other comments.

                 

                Also, if you have any suggestions on my 3 approaches, I'd be happy to receive them.

                 

                @Ann,

                 

                Neatvideo 3.0 and later provides support for GPU and CPU and it is significantly faster than previous versions which couldn't take advantage of GPU.

                • 6. Re: Use Previews - to use them or not for final export
                  Ann Bens CommunityMVP

                  In your case I would not use the preview files for final render.

                  Premiere does not see Neat Video as a GPU accelerated effect.

                  • 7. Re: Use Previews - to use them or not for final export
                    Nanda_KP Community Member

                    Can you provide a reason for not advising to use preview files for final export to H.264, given that the data on the preview files indicates that they are at least as good as the source clips?

                    I am just a little confused then about what would be the 'right' way to create a final version of the multicam sequence:

                     

                    Since you comments do not approve either approach 2 or 3, I assume approach 1 is what you would use:

                    approach 1:

                    - tune the effects on the clips to my satisfaction

                    - disable them on source timeline (resulting in green/no render bar which will allow me to playback in RT without issues)

                    - create multicam sequence from them

                    - go to each clip in multicam sequence and re-enable the effects and then kick off the Export on the multicam sequence

                     

                    The final export will be to H.264 for Bluray.

                     

                    Regd. Neat Video:

                    Correct, Premiere does not see NeatVideo as a GPU accelerated effect

                    - however, it is a fact that NeatVideo does use GPU: Neat Video :: features,    Neat Video :: overview

                    • 8. Re: Use Previews - to use them or not for final export
                      Ann Bens CommunityMVP

                      When using avchd most of the time the preview codec will be i frame only mpeg.

                      • 9. Re: Use Previews - to use them or not for final export
                        Nanda_KP Community Member

                        Thank you - I'll keep that in mind.

                        But I was told that MPEG-2 I-Frame and ProRes are quite similar in terms of edit friendliness and lossyness (can survive generational loss)

                        • 10. Re: Use Previews - to use them or not for final export
                          JSS1138 CommunityMVP

                          ProRes will likely withstand generation loss much better than MPEG, even I-frame.

                          • 11. Re: Use Previews - to use them or not for final export
                            R Neil Haugen Community Member

                            You are mixing playback and export codecs & use ... two very different things. PrPro is a "non-destructive editing" program like Lightroom ... it creates previews ONLY with the intent to give you something that shows the original image AS MODIFIED by the instruction set of the choices you've made in editing/grading/fx. It does NOT create previews of the entire sequence, there is no file created that you are watching on the playback monitor ... and it only creates previews for those bits of timeline you specifically request it to do so. The entire "preview" process is just designed to get you through playback while editing as smoothly as possible. Nothing more.

                             

                            PrPro does not create "full" files for previews, as those above have stated ... it uses highly compressed but fast-computed codecs for making previews in a render-work-area situation as those previews are assumed to be used ONLY for playback while editing. There is no intent in the design of the program to use out-put style codecs as previews. About the only time the previews might actually be usable is if you are outputting DPX files, and have previews set for that  HUGE space-hog format (I think that's an example from somewhere). Well, or if you're outputting to a very small frame-size anyway.

                             

                            So ... basic "data" of the preview files might not be too bad, as far as bit-rate/file-size and all ... but the actual images are not going to be of the higher quality you'll need for a final export render-out for use. Do NOT confuse quick & dirty preview codecs for playback purposes with sit-down to a 52" TV & watch output codecs.

                            • 12. Re: Use Previews - to use them or not for final export
                              Ann Bens CommunityMVP

                              The only time when preview files are usefull is when you want to make a quick export (say for review) where quality is not an issue.

                              • 13. Re: Use Previews - to use them or not for final export
                                Nanda_KP Community Member

                                Thank you all for your comments. that answers my questions.