5 Replies Latest reply on Nov 17, 2014 9:35 PM by fastnoc

    Can someone explain two pass encoding and tell me why i would use it?

    fastnoc Level 1

      I'm somewhat new to AE, Been using it only for about 1.4 years, however I've produced around 200 videos (short effects clips).


      I don't understand some things, and one of them is the two pass encoding option.

       

      Clearly there's a reason for it but I did a search and I don't find much explaining why i would use it.

       

      Can someone help a relative newbie?

        • 1. Re: Can someone explain two pass encoding and tell me why i would use it?
          fastnoc Level 1

          By the way, I did find this:?

           

          VBR, 2 Pass

          Variable bitrate, with the encoder making two passes through the file, from beginning to end, and then from end to beginning. The second pass prolongs the process, but it ensures greater encoding efficiency, and often a higher-quality output.

           

          But i don't understand how it would ensure greater efficiency? if I understand it right it renders forward then backwards. How does that help?

          • 2. Re: Can someone explain two pass encoding and tell me why i would use it?
            Rick Gerard Adobe Community Professional & MVP

            Two pass encoding doesn't render frontwards and then backwards. Codecs that use multiple pass rendering deliver the video as a series of full frames that have all of the data mixed with frames that only contain the best guess of which pixels change between the full frames. The first pass makes a pretty good guess at the partial frames and then the partial frames are compared with the originals one more time checking on both sides of the partial frames to see if better calculations can be made. This improves the accuracy of the calculations, reduces the data rate, smooths out color and motion artifacts, and increases perceived sharpness in the stream. The quality is always better. The playback is easier on the CPU because the data is packed in a more efficient package for decoding. Multiple pass rendering does take more time to render so the efficiencies are in the playback, data rate and perceived perception of higher quality video. I never deliver single pass rendering to a client.

             

            I hope that explanation helps. It's just like any other system of making mathematical projections. The more times and the more ways you look at the data the more accurate the result.

            • 3. Re: Can someone explain two pass encoding and tell me why i would use it?
              fastnoc Level 1

              hrm, not sure what you mean it doesn't go front to back, that's what the definition says. Maybe I'm understanding it wrong.


              Whatever the case, this is a pretty enlightening answer, and I'm going to take some time and use this. I wonder if this would mean I could lower the bit rate a touch because I've been raising that to gain clarity.

               

              Thank you very much for that answer Rick, that's exactly what i was wanting to know.

              • 4. Re: Re: Can someone explain two pass encoding and tell me why i would use it?
                fastnoc Level 1

                OK while we're on this subject, let me ask you one other thing.

                 

                When rendering for vimeo or youtube do you have suggestions on optimization? both of them stomp so hard on my videos they look bad. Well, not 'bad' but they aren't crisp and clean.

                 

                Now I've seen other videos up there that are nice, so what could I be doing wrong? is there a way to improve output for those sites?

                 

                here's an example I just uploaded. Notice how it's OK, but it's NOT crystal clear, and it sure is in the original. FYI I did upgrade this to 1080p

                 

                EDIT: Wow I just noticed an error. in scene 3 it says 'a video effects presentation'. for one, it's too low, but i also seem to have duplicated the word 'a'. ugh...l now I wish i'd rendered this as a sequence so i could fix it. but now I spose I'll have to fix it, and render out just that scene and splice it in.. ugh

                 

                 

                 

                direct link: Vide link on Vimeo

                • 5. Re: Re: Can someone explain two pass encoding and tell me why i would use it?
                  fastnoc Level 1

                  Actually i think I replied to myself I mean to reply to you (above)