15 Replies Latest reply: Sep 23, 2011 6:07 AM by joe bloe premiere RSS

    RAM preview quality vs. render quality

    joe bloe premiere Community Member

      Is there any difference in image quality between a targa sequence

      output as the result of a saved full resolution RAM preview and

      the same comp rendered to a targa sequence at full resolution

      via the render queue?

       

      I have specified targa sequence as the default format for saving

      RAM previews within the output module template.

       

      I can see no difference.

        • 1. Re: RAM preview quality vs. render quality
          Rick Gerard CommunityMVP

          Just the ability to control the render. You can't change things like the way the alpha is rendered without using the render cue. I don't think it's a very professional workflow and I'd never do it except maybe for a quick, must make the deadline preview for a client.

           

          That would probably be unlikely though because my previews are all web based not and going directly from an AE comp to the Media Encoder to the YouTube of Vimeo HD presets for render would be just as fast if not faster than doing a full project ram preview (even if I had the ram for it), saving the sequence, then compressing it for the web.

          • 2. Re: RAM preview quality vs. render quality
            joe bloe premiere Community Member

            Just the ability to control the render.

            So, there is no image quality difference between the two

            if the export codec is the same?

            You can't change things like the way the alpha is rendered without using the render cue.

            When I specify .tga sequence as the output format for RAM previews, there appears to be

            options in the Output Module Settings dialog for 32-bit, premultiplied and straight.

            • 3. Re: RAM preview quality vs. render quality
              Rick Gerard CommunityMVP

              You're right about setting the options for Ram Preview, which is OK if you remember to do that every time or you always want the same thing. I also never work with targa sequences because it doesn't fit my workflow or delivery pipeline. I think there's better image sequence options.

               

              The biggest reason that I don't use that workflow is that It's too slow. I'll bet that I haven't rendered a full resolution ram preview longer than 10 frames twice in the last 5 years. Most of the time I work at 1/2 or even 1/4 rez in the comp window when previewing because I'm only checking motion. I check the composite a frame at a time most often at 200%. I haven't got time to sit around and wait for 20 or 30 seconds of ram preview at full rez and only a few of the places that I work have a monitor that will show me a full frame full rez preview. Once the project's done I fire it off to the media encoder or cue it up for rendering later and then I start working on something else.

               

              If your workflow is different then that's OK. My workflow is what works best for me and it's only offered as a suggestion. 

              • 4. Re: RAM preview quality vs. render quality
                joe bloe premiere Community Member

                Thanks for your input.

                I have used .tga output of a RAM preview as an example, but

                I use other lossless formats (Lagarith/UT) for outputting RAM

                previews as well depending on the circumstances.

                 

                As part of my standard workflow, I will always view a full resolution

                RAM preview of an AE comp before I consider it finished.

                If there is no quality difference, why not write the frames that are

                already rendered into RAM as an uncompressed image sequence?

                 

                Just to affirm, there is no quality difference, right?

                • 5. Re: RAM preview quality vs. render quality
                  Fuzzy Barsik Community Member

                  Unfortunately, I can't find Todd's explanation quickly...

                  • 6. Re: RAM preview quality vs. render quality
                    joe bloe premiere Community Member

                    I have this from April:

                    Set codec for saved RAM preview?

                     

                    Does anyone know definitively whether or not there is any

                    compromise to image quality if a RAM preview is saved to

                    a lossless codec vs. rendering to the same codec using

                    the render queue?

                    • 7. Re: RAM preview quality vs. render quality
                      Rick Gerard CommunityMVP

                      As far as I know - No difference.

                      • 8. Re: RAM preview quality vs. render quality
                        Dave LaRonde Community Member

                        Just to affirm, there is no quality difference, right?

                         

                        There could be one single deal-breaker:  I believe a rendered targa sequence supports transparency, but a RAM Preview doesn't.  If that's an important consideration, I'd render the targa sequence.

                        • 9. Re: RAM preview quality vs. render quality
                          joe bloe premiere Community Member

                          Thanks for your input, Dave.

                           

                          I have just saved a RAM preview using the Output Module settings below,

                          and the result is a 32bit .tga sequence with premultiplied alpha.

                          RAMpreview.png

                           

                          As I understand it, the only limitation is that a RAM preview doesn’t generate

                          interlaced fields, so this method is only valid for a progressive composition.

                          • 10. Re: RAM preview quality vs. render quality
                            Dave LaRonde Community Member

                            As I understand it, the only limitation is that a RAM preview doesn’t generate

                            interlaced fields, so this method is only valid for a progressive composition.

                             

                            That's my understanding, too.  If you haven't done so already, I also recommend double-checking on the type of alpha channel to be delivered: Premultiplied or Straight.  And I learned something new today as well, so thank you.

                            • 11. Re: RAM preview quality vs. render quality
                              joe bloe premiere Community Member

                              I also recommend double-checking on the type of alpha channel to be delivered: Premultiplied or Straight.

                              This is a method I use internally for DI's... so no delivery concerns.

                              And I learned something new today as well, so thank you.

                              I believe if someone knew everything there is to know about AE,

                              it's likely their head would explode.

                               

                               

                              Thanks again for your input.

                              • 12. Re: RAM preview quality vs. render quality
                                Todd_Kopriva Adobe Employee

                                Sorry to chime in so late. Busy day.

                                 

                                If you're rendering a RAM preview at full frame rate and full resolution from your active camera view, then what's stored in the RAM cache is an uncompressed set of frames that represents the same as what you'd be rendering as the first phase in the rendering process through the render queue. (Note all those caveats, though.)

                                 

                                Note that rendering and exporting throught he render queue involves two phases: rendering (controlled by render settings) and encoding/compression/format-conforming (controlled by output module settings). Saving a RAM preview means that you're skipping the first phase and using what's saved in RAM; but you still need to consider the second phase. You can set up any kind of output module settings that you like for saved RAM previews.

                                 

                                Personally, I never use the ability to save RAM previews. I tend to do RAM previews in pieces or at partial resolution or partial frame rate so much that I never have a full green bar for my entire composition just sitting there waiting to be encoded and exported.

                                • 13. Re: RAM preview quality vs. render quality
                                  joe bloe premiere Community Member

                                  Thank you Todd for the detailed clarification.

                                   

                                  I don't save my RAM previews in all instances... usually linked comps

                                  that I know will slow a final render and export in Premiere if I don't use a DI.

                                  Like you, I would never use the 'Save RAM Preview' function if the render queue

                                  would recognize and utilize the frames that are already rendered into RAM.

                                   

                                  If the 'RAM Preview Options' are identical to the 'Render Settings' in the Render Queue

                                  (i.e. full frame rate, full resolution, active camera view),  the queue should see and use

                                  any frames sitting in RAM, skip to the 'Output Module' and write the file(s) to disk.

                                  Instead, the Render Queue ignores the already rendered frames waiting in RAM,

                                  and starts over rendering every frame again.

                                  For example, if you have rendered every third frame at full resolution as a RAM preview,

                                  the render queue should see those frames and just send them to the Output Module

                                  and only need to render the two in-betweens.

                                   

                                  By setting RAM Preview Options to full frame rate, full resolution, active camera view,

                                  I can essentially skip directly to the Output Module by saving the RAM preview.

                                  The primary benefit is that I can output the same RAM preview to multiple Output Module

                                  settings without re-rendering the frames by using the Output Module Templates dialog

                                  box to choose a different output module template for RAM Preview, and re-exporting.

                                  These differently formatted outputs will utilize the frames waiting in RAM, and do

                                  not require any additional rendering time... only the time to write the file(s) to disk.

                                   

                                  If you send a comp to the Render Queue, choose an Output Module, duplicate the

                                  pending render without changing the Render Settings but change the Output Module,

                                  the queue will render all of the frames twice in order to write to the two outputs.

                                  Saving two RAM previews cuts this time in half.

                                   

                                  Unless I have missed something, I suppose this is a feature request?

                                  • 14. Re: RAM preview quality vs. render quality
                                    TimeRemapper Community Member

                                    Select your queued render item, and choose "Add Output Module" from the Composition menu. You can add as many Output Modules as you want to any queued render item. However, I dig what you're saying about freezing pre-processed frames. It could happen with a more successful disk cache strategy in the future, I would imagine.

                                     

                                    Overall, by adding multiple Output Modules, it seems it would effectively do what you want (process a frame once, but write it X number of times to X number of files), other than using the existing render data used by generating the RAM preview.

                                    • 15. Re: RAM preview quality vs. render quality
                                      joe bloe premiere Community Member

                                      Aha!  So, I did miss something:

                                      Multiple output modules assigned to a single render item.  Thanks for that.

                                       

                                      But... if I take the time to do a RAM preview, those rendered frames are still not

                                      utilized in the final output if I use the render queue instead of a saving a RAM preview.

                                       

                                      I suppose this should be the feature request?

                                      If the 'RAM Preview Options' are identical to the 'Render Settings' in the Render Queue

                                      (i.e. full frame rate, full resolution, active camera view),  the queue should see and use

                                      any frames sitting in RAM, skip to the 'Output Module' and write the file(s) to disk.

                                      For example, if you have rendered every third frame at full resolution as a RAM preview,

                                      the render queue should see those frames and just send them to the Output Module

                                      and only need to render the two in-betweens.