8 Replies Latest reply on Aug 5, 2009 8:40 AM by the_wine_snob

    Popping sounds when transcoding wmv to flv with media encoder

    prifel

      Whenever I use adobe media to transcode a wmv file created in windows media encoder to a flash file, I get pops  in the audio track (similar to hissing bacon). The pops only occur during the begining of the video, when it's quiet and go away once the music or any loud noises begin. I did some research and found that it's a common problem when changing sample rates but the thing is that it doesn't happen on every conversion, and happens across multiple computers. We've tried it on Dell precision m65s (xp pro) as well as a Dell xps (vista 64bit) and a MacBook pro running xp pro in bootcamp. Here are the settings we use in windows media encoder: 1800kbps video 160kbps CBR audio at 48khz 640x360 resolution 29.97 fps keyframe: 8 seconds  And here are the settings we use in AME: flv multiplexing on2 vp6 codec 2 pass vbr at 800kbps "undershoot" at 100% (quality: best) mp3 audio at 160 Kbps we have found that these settings work best for our cdm (brightcove)   Again, it only happens at the begining of a video when it is quiet. Does anyone have any idea what could be causing this? Before anyone asks, the reason we don't capture it directly into flash with live flash media encoder is because the motion in our content causes the processor to peak resulting in dropped frames. When we get better equipment we will switch to live flash media encoder but until then we are stuck with windows media encoder.  Thanks, Peter

        • 1. Re: Popping sounds when transcoding wmv to flv with media encoder
          Jim_Simon Level 8

          Query:  Why are you starting with WMV?  That is normally something you end up with, not something you start with.

          • 2. Re: Popping sounds when transcoding wmv to flv with media encoder
            the_wine_snob Level 9

            Are the .WMV files your source Assets? What are the audio specs of these files?

             

            As Jim asks, why start with .WMV files for anything, as they are heavily compressed and are delviery format files to begin with? Can you not get back to before the processing to .WMV?

             

            I'm also a bit surprised that one can hear much of anything with MP3 Audio. I find that all of the higher (above mid-range) and lower (anything below about 250Hz) is lost in that compression. Your ears must be better than mine to pick up any irregularities with that heavily compressed material.

             

            To determine where the Audio problems were being introduced, I'd listen carefully to the material at each step of you workflow. If it's in the Export to FLV, then another alternative could be to use a program, such as F4V to do the conversion to FLV.

             

            From what I am reading, these problems could come in anywhere in the workflow. A bit more detail, especially the exact, and full specs. of your source material might yield a clue.

             

            Good luck, and hope that someone can spot the exact problem from the answers to the above questions,

             

            Hunt

            • 3. Re: Popping sounds when transcoding wmv to flv with media encoder
              prifel Level 1

              Again, the reason we are capturing with Windows Media Encoder is because we tried using Live Flash Encoder to capture directly into flash but our equipment wasn't fast enough and it was dropping frames all over the place.  We also don't have the space to capture into an uncompressed format because we don't have the available storage, and our events can be 8 hours long or more (each video is about 15 minutes, 20 or more videos)

               

              Ive listened to everything in my workflow and it sounds fine until the outputted FLV file from AME.

               

              WME is capturing at the following specs:

              160kbps 48KHz Windows Media Audio 9.2 codec (stereo) 1 pass CBR

              1800kbps 1 pass CBR video

              29.97 fps

              640x360 resolution

              buffer size: 5 seconds

              key frame interval: 8 seconds

               

              I have verified this with a codec info utility I ran on the wmv files.

               

              AME is encoding with the following specs:

              FLV Multiplexing

              On2 VP6 codec

              620x360 resolution

              800kbps 2 pass VBR

              100% undershoot at best quality

              160kbps stereo MP3 audio

               

              I verified the above with the same codec info utility (gspot 2.70a) and it is all acurate, it also told me that the audio is at 44.1KHz rather than 48 (there was no place to specify this, is this a limitatino of the VP6 codec?)

               

              Yes, these are our source assets.  They're being captured either through an XL2 via firewire, or from an analog program feed converted to firewire via a Canopus converter box.

               

              If anyone has any suggestions on how to get rid of this, or a different encoder (either to capture with rather low cpu resources, or to encode into flash) let me know.  I can provide a sample of the clipping if you need

               

              Thanks,

               

              Peter

              • 4. Re: Popping sounds when transcoding wmv to flv with media encoder
                Harm Millaard Level 7
                Again, the reason we are capturing with Windows Media Encoder is because we tried using Live Flash Encoder to capture directly into flash but our equipment wasn't fast enough and it was dropping frames all over the place.

                 

                This is the first time I have heard anyone trying to capture with WME or Flash. Normally you capture with PR or alternative software. Since this is a first, you are on your own. Just as when you try to copy a book on a shelf into a Word document. Not much chance of success. Chances increase when you get the book off the shelf, put it on a scanner and use text recognition software for import into a .doc file.

                • 5. Re: Popping sounds when transcoding wmv to flv with media encoder
                  prifel Level 1

                  The reason that we've been capturing with WME is because most of the events are also being streamed live using WME through our CDM so we decided to stick with the same software and just use higher bitrates for the capture to be uploaded for On Demand later.  Thanks anyway

                   

                  Does anyone have ideas for other software that can capture into a compressed format?

                  • 6. Re: Popping sounds when transcoding wmv to flv with media encoder
                    the_wine_snob Level 9

                    An odd workflow to me, but what I did not notice was if you were able to pinpoint WHERE the Audio problem was being introduced. Were you able to pinpoint that, by testing the Audio along your path? BTW, the 44.1 to 48KHz upsampling should not be an issue. PrPro normally handles that easily and cleanly.

                     

                    Can you verify that the Audio is squeaky clean, prior to Import into PrPro?

                     

                    Good luck,

                     

                    Hunt

                    • 7. Re: Popping sounds when transcoding wmv to flv with media encoder
                      Jim_Simon Level 8

                      Does anyone have ideas for other software that can capture into a compressed format?

                       

                      OnLocation.  It captures to DV, which really is what you aught to be using if any kind of further editing or transcoding is going on.  Using a Laptop with a mere 300GB drive will do the job perfectly for 8 hour sessions.

                      • 8. Re: Popping sounds when transcoding wmv to flv with media encoder
                        Harm Millaard Level 7

                        CAPTURING is a digital transfer of data as they were recorded on tape. All the recorded 0's and 1's are being transferred as they are. Nothing more, nothing less. From your post it looks like you are using incorrect terms for what you want to accomplish. So help us out by using the proper terminology. Start with correct and exact descriptions, maybe after some basic education in video editing, so you know what the terms mean and we can understand you.