12 Replies Latest reply on May 22, 2014 7:32 AM by A.T. Romano

    AVCHD CBR bitrate settings don't match output

    <videoking>

      I had to lifecycle computers at work and to make a long story short, it was much easier for me to switch to PREL 12 than continue to use PPro.  The export/publish & share process is pretty similar, but I have been frustrated by trying to produce an H.264/AAC mp4 with a CBR setting for the video of 5mbps (I have a 50 minute video I'm trying to keep under 2Gb or it would be 6.)  The estimated file size is about 1.9 Gb with these settings but the actual file is closer to 1.2Gb and the property inspector for the file shows a video data rate of 2791 Mbps instead of an even 5.  I'm using the exact same settings I used for export in Pro - 1920x1080, Baseline 4.0 at 29.97fps.   I have mucked about with different profile levels from 4.0 to 5.1, high, main and baseline settings and none of it seems to matter, it won't produce the CBR I've specified - even setting it at 10mbps still only got me to about 3.5 on the actual file.  Anyone have a fix/workaround/suggestion for this?

        • 1. Re: AVCHD CBR bitrate settings don't match output
          A.T. Romano Level 7

          video

           

          Please excuse the questions, but I did not want to take anything for granted.

           

          Please consider if you are really talking about a constant bitrate or the setting of CBR vs VBR.

           

          For example, if you are in Publish+Share/Computer/AVCHD with Presets = MP4 - H.264 1920 x 1080p30, under the Advanced Button/Video Tab, you will find

           

          Bitrate Encoding with 3 choices

          CBR

          VBR, 1 Pass

          VBR, 2 Pass

           

          If I set for CBR and 5 Mbps, then I get an export with bitrate at CBR 5 Mbps. However, in the VBR settings, you are dealing with a variable bitrate with a set Target and Maximum. The end result will depend on the settings and the nature of your video.

           

          So before we go further, please confirm if you are OK with the concepts of CBR and VBR.

           

          http://en.wikipedia.org/wiki/Constant_bitrate

           

          http://en.wikipedia.org/wiki/Variable_bitrate

           

          Thanks.

           

          ATR

          • 2. Re: AVCHD CBR bitrate settings don't match output
            <videoking> Level 1

            Yes, I know the difference between CBR and VBR and the output description does say CBR 5.00.   Have you done this yourself with exactly the parameters I have described and checked the actual output, either by comparing the estimated file size against what is created and/or inspecting file properties?   I did this with files created by Media Exporter (via PPro) using the same settings for dimensions, H.264 profile and bitrate and those files show a video bitrate of exactly 5000 Kbps, whereas the PREL file does not.

            • 3. Re: AVCHD CBR bitrate settings don't match output
              A.T. Romano Level 7

              videoking

               

              Yes. Road tested to verify just in case you asked.

               

              Here is what I did. If you see any modifications in the testing that you would like me to cross check with you, please let me know.

               

              Source was a H.264.mov files (Bitrate 45.8 Mbps, file size 166 MB)

              All properties were reads from MediaInfo (Tree View)

              For the source H.264.mov (file size 166.3 MB)

              OriginalBitrateTest.JPG

               

              Taken Into a Premiere Elements 12 project set a NTSC/DSLR/1080p/DSLR 1080p30.

              Publish+Share

              Computer

              AVCHD with Presets = MP4 - H.264 1920 x 1080p30

              Export Settings Dialog

              ExportSettings.JPG

               

              And, the MediaInfo properties readout for the export (file size 18.2 MB)

              CBRBitrate.JPG

              I did not alter any of the settings under Advanced Button/Audio Tab.

               

              Please review that above and then let me know what supplemental information you need.

               

              Thank you.

               

              ATR

              • 4. Re: AVCHD CBR bitrate settings don't match output
                <videoking> Level 1

                As you can see from the attached screen caps, your results and mine vary. Note the difference between the estimated file size of 1943.04 for a 5 Mbps file (consistent with the size of files I've successfully exported from PPro) and the actual size of the file at 1.107 Mb, and the File Explorer properties description of the file showing a definitely-not-5Mbps bitrate (which accounts for the actual size being smaller than the estimate.)

                 

                PREL export settings.png

                 

                PREL export file info.png

                 

                If you have suggestions on what settings to change to address this issue, let me know, pearing in mind that I have already experimented with different Profile and Level values.

                 

                Thanks,

                 

                John

                • 5. Re: AVCHD CBR bitrate settings don't match output
                  <videoking> Level 1

                  Well, I think I have figured out what is going on, via the MediaInfo panel (thanks clueing me into that app, very handy!)   The video is in fact rendered CBR, but when the mp4 multiplexing happens, it's VBR! That seems super dumb to me and I don't see a way to adjust it, so I may be stuck...

                  • 6. Re: AVCHD CBR bitrate settings don't match output
                    A.T. Romano Level 7

                    videoking

                     

                    Thanks for the follow ups.

                     

                    I went back and re-checked all that I have posted for you so far. For completion, the MP4 H.264 1920 x 1080 p30 default settings remained the same under Advanced Button Audio Tab and Multiplexing Tab. Only the Advanced Button Video Tab settings were adjusted to saw the values already present. The Advanced Button/Multiplexing Tab settings were: Multiplexing = MP4 and Stream Compatibility = Standard. The Video bitrate encoding was again set a CBR and the bitrate set at 5 Mbps. Same 18 MB estimated file size. And, when I looked at the properties of the export same as before. File size 18.2 MB with bitrate 5 Mbps. All per the MediaInfo properties readout. The GSpot readout told me that the file had a bitrate of 5031 kbps (4.91 Mbps) and a file size of 18.2 MB.

                     

                    I do not use the VLC player except on rare occasions and not for a properties readout. But when I saw your VLC properties readout for your file, I decided to give  VLC player's Media Information a look. And, saw what you are probably have been looking at under Input Bitrate...values varying below and above the 5 Mbps bitrate of the file (roughly between 4.8 and 5.6 Mbps). I do not see those types of differences responsible for your 1943.04 to 1.107 MB file sizes (both under the CBR 5 Mbps condition. I have not found a way to control what the VLC player is doing with the file.

                     

                    So, I find it curious why you were not seeing the same things with Premiere Pro VLC Player as compared to Premiere Elements VLC Player. It is this point that causes me to think and re-think your issue.

                     

                    In view of the circumstances, have you posted your question in a VLC player related forum? I suspect that answer is "it is what it is". But nothing is written in stone without more input from the people deeply involved with the VLC player and its offerings.

                     

                    Please check out the above and determine if I have interpreted your issues correctly.

                     

                    Thanks.

                     

                    ATR

                    • 7. Re: AVCHD CBR bitrate settings don't match output
                      <videoking> Level 1

                      That info panel is actually from Windows Explorer, the VLC icon just indicates that it's the default program for playback of that type (.mp4) file.   The actual issue, as I stated in my last message, is that (according to MediaInfo) the mp4 multiplexing of the CBR m4v and aac files is executed as a VBR, not CBR, operation.  PPro doesn't do this and I'm not sure why PREL does but since there isn't a setting to change/adjust that behavior, it's a moot point.  Fortunately I have Production Premium on my home system so if I really want to render this file properly, I have another option, but it just sucks that I can't fix this situation within Elements.

                       

                      Thanks for your interest in this issue - if nothing else I was introduced to MediaInfo because of it!

                      • 8. Re: AVCHD CBR bitrate settings don't match output
                        A.T. Romano Level 7

                        videoking

                         

                        Thanks for the follow ups.

                         

                        You wrote

                        The actual issue, as I stated in my last message, is that (according to MediaInfo) the mp4 multiplexing of the CBR m4v and aac files is executed as a VBR, not CBR, operation.

                        Could you point out to me where in the MediaInfo Tree View properties readout you are finding the information on which to base your conclusion...."executed as a VBR, not CBR, operation".

                         

                        As per the details already provided, I am seeing only an estimated 18 MB file ending up as an actual 18.2 MB file....CBR, Video Bitrate, before and after export 5 Mbps. What am I overlooking in what you are trying to tell me?

                         

                        Thanks.

                         

                        ATR

                        • 9. Re: AVCHD CBR bitrate settings don't match output
                          <videoking> Level 1

                          Sorry, I should have included that screenshot:  PREL mediainfo tree.png

                          • 10. Re: AVCHD CBR bitrate settings don't match output
                            A.T. Romano Level 7

                            videoking

                             

                            That is "wild". I have never run into that combo

                            Bitrate Mode: Constant

                            Bitrate: 2708 Kbps

                            Nominal Bitrate: 5000 Kbps

                             

                            You have already presented a screenshot of your Export Settings under the Advanced Button of the preset = MP4 H.264 1920 x 1080p30. And, it looks like what I have here for my tests. What are the settings under your Multiplexing Tab? Are they the same as I reported in a prior post?

                             

                            If all settings appear to be the same from there to here, any chance of you posting a Dropbox link to a sample in your thread?

                             

                            Thanks.

                             

                            ATR

                            • 11. Re: AVCHD CBR bitrate settings don't match output
                              <videoking> Level 1

                              Our multiplexer settings are the same (really not much to choose from there - i did try "None" instead of mp4 and all that does is not combine the m4v and aac files.)   I have the output file in Dropbox, but I'm not sure how that would be helpful and the input is actually a slideshow of 600 stills set to music.

                               

                              So, thanks for your interest, but I'm not sure there's anything more to be done here.   If you hear of a way to adjust the multiplexing settings, please let me know!

                              • 12. Re: AVCHD CBR bitrate settings don't match output
                                A.T. Romano Level 7

                                videoking

                                 

                                Thanks for the reply.

                                 

                                I still cannot pick up on the difference between your Premiere Elements and Premiere Pro results with regard to your bitrate/file size (estimated and actual) issue. I am not seeing it in the comparable setup that I have used. I wish I could reproduce your results so that I could work on it.

                                 

                                But I understand your thoughts to move on. If any related information develops, I will surely post it in your thread.

                                 

                                We are glad for the opportunity to be of assistance now or in the future.

                                 

                                Best wishes

                                 

                                ATR