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Thread: AVCHD to FLV/F4V = hiccups in audio

  1. #1
    Junior Member
    Join Date
    Apr 2002
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    Memphis
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    27

    AVCHD to FLV/F4V = hiccups in audio

    I need some help with a problem that I can’t seem to find any information about.

    First the project - I have a player that I have developed in Flash that reads an audio-only FLV file and uses the FLV’s embedded cue points to load “slide images” as they are needed. The initial video has been shot with a Canon HF20. I am editing the files directly from the camera and from an external eSATA drive with Premiere Pro CS4. In Premiere, I am combining the MTS files and adding the cue points using the video to reference when the presenter changes the slides. The audio sounds perfect in Premiere. I then export the audio as an FLV (I have also tried using F4V to try and fix my problem).

    Now the problem – The audio files, which vary in length from 2 minutes to 2 and a half hours, come out of the Adobe Media Encoder with spots of skipped audio (as if they had been dropped frames when encoding). A couple of times I’ve even had “misplaced” audio – where a second or two of audio from one part of the file plays in another section. Listening to the same file more than once shows the problem is in the file, not a playback error (such as something else being processed in the background causing the skip). Also, AME does not report any compiling errors for these files.

    Here’s the technical stuff -
    Original files are AVCHD from the Canon HF20. Premiere gives the files’ frame rate as 29.97 and audio format as 48000 Hz, compressed, Stereo and the project’s audio format as 48000 Hz, 32 bit floating point, Stereo.
    I am encoding the files as audio only, bitrate 96kbps, Stereo for the FLVs and 44.1kHz, bitrate 96kbps, Stereo, using AAC for the F4Vs.
    My computer’s specs are Pentium 4, 2.8 Ghz with 4 GB of RAM. XPPro with SP3. I am encoding the final FLV’s to an external 1 TB HD connected via eSATA.

    I appreciate any help/advice that anyone might have on this. I know my computer isn’t the best for video editing, but the main reason for this setup was to process the camera’s digital files to audio. If the computer’s processor is what’s causing the hiccups, then I’ll need to upgrade. If you need any more info from me, please let me know. Thanks again!

  2. #2
    Senior Member
    Join Date
    May 2008
    Posts
    332
    Your project description is a little confusing..
    I have a player that I have developed in Flash that reads an audio-only FLV file and uses the FLV’s embedded cue points to load “slide images” as they are needed. The initial video has been shot with a Canon HF20.
    What video? What slide images? I thought this was an audio-only FLV file?
    The audio files, which vary in length from 2 minutes to 2 and a half hours, come out of the Adobe Media Encoder with spots of skipped audio
    So how was the AME used? Did you use it to capture the live audio? If so, what about the Canon HF20, was it fed into the AME or did you use some other audio input? If the audio file was corrupt at that point, how can it possibly get any better?
    the project’s audio format as 48000 Hz, 32 bit floating point, Stereo.
    This doesn't specify the format, just the specs. So was the .flv encoded with mp3 and the .f4v with ACC?
    Since .flv is just a container format, not an audio or video format, you can break the container open anytime and extract the audio or video components and test their integrity. You may need to do that at various points in your project with something like "flv extract". Google for latest version. Then test/play the separate audio and video components.
    So with all the confusion, it seems that the problem is creating a perfect audio file first, and then later, adding cue points. Is that a correct understanding?
    Best wishes,
    Eye for Video
    www.cidigitalmedia.com

  3. #3
    Junior Member
    Join Date
    Jun 2003
    Posts
    27
    Original files are AVCHD from the Canon HF20. Premiere gives the files’ frame rate as 29.97 and audio format as 48000 Hz, compressed, Stereo and the project’s audio format as 48000 Hz, 32 bit floating point, Stereo.
    Sounds like the 48 kHz and the 32-bit floating point are the source of your issues. If this for a video then it is likely a WAV file (If I'm understanding everything correctly). I would try dithering your wav file to 41kHz and 16-bit (using adobe sound canvas- if that would work, or, adobe audition- which I know would work).

    the process would run like this- export audio from Premiere, bring it into audition, save (re-sample) as 16-bit, 41kHz... import this new Wav back into Premiere... delete the original wav file or turn it off. now export as FLV.

    I hope this helps. I'm guessing here!

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