But extracting the audio separately and adding it to another type of movie file, such as an MPEG-4 or H.264 file, removes any timing information from the audio stream. MPEG decoders can use timing information embedded in each video and audio sample to compensate for corruption and/or the disappearance of parts of the source data. Video/audio stream discrepancies are normally handled transparently by the MPEG standard's advanced timing mechanisms. Synchronization problems are well known to those experienced in re-encoding MPEG-1 and MPEG-2 source files. Essentially this means that an MPEG-1 or MPEG-2 file that you plan to convert may export with excellent audio and video synchronization, but there is really no guarantee. We repeated our tests with several leading video conversion tools and their results ranged from somewhat less successful to slightly more successful than our own success rate. The remaining tests resulted in synchronization issues, unpredictably ranging from slight to very noticeable. During our research we experienced successful audio and video synchronization in over 80% of our test files.
We're pleased to say that by extracting the audio independently of QuickTime ViddyUp! does export both video and audio from most MPEG-1 and MPEG-2 sources.Īudio and video synchronization for these files, however, is hit or miss. This presented a challenge to ViddyUp!, which is based on QuickTime. MPEG-1 and MPEG-2 are not fully supported by QuickTime, which can only export the video from source data in these formats.
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