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I'm wondering how reliable the Apple Compressor is. I'd like to convert a photo JPG to an MP4 file and am hoping to do it in a fashion that does not "unsync" anything audio/video related.

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Not quite sure what you mean. Are you saying you have a photo and want to add sound to it by converting it to a video? –  Andrew Spitz Mar 18 '11 at 8:15
    
NO no, the movie is in JPEG format –  Chris Mar 18 '11 at 16:56
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4 Answers

up vote 6 down vote accepted

I'm going to assume that you mean you have a Movie in Photo-JPEG codec (yes it IS a valid legacy Quicktime Format), and would like to convert it to MP4. Compressor simply uses the Quicktime Engine, so as far as sync goes it will be no better or worse than anything else (i.e. FFMPEG or anything that uses that specific engine). Like @georgi.m said, stick with common frame rates and sample rates.

Bear in mind that Photo-JPEG is an INTRA frame codec, while MP4 is an INTER frame codec, which means that rather than individually compressing each frame, the movie is compressed in Groups of Pictures (GOP). Essentially the start, middle and end of each GOP is compressed and then the frames in-between are interpolated (oversimplification, but gets the gist). The end result is much lower data rate for a given picture. However the tradeoff is that the CPU (as opposed the the Hard Drive) has to work harder to decode the movie. The other tradeoff is that the Audio and Video streams are decoupled for decode than re-integrated on the playback. In theory this works fine, but in practice, a slow computer or slow connection WILL result in sync being off (it taking longer to decode the video than the audio). This has NOTHING to do with the program used to encode the MP4, and everything to do with the computer playing it back.

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why is photo-jpeg a "legacy" format? –  georgi May 18 '12 at 14:32
    
Because Apple has decided it so! :) Basically Apple is pushing h.264 and ProRes, so they took some of the older codecs that had been around for a while and made them "legacy". They have to be enabled in Quicktime 7 and are missing from QT X entirely (although they can be added back in manually, or by enabling QT 7 on the system) –  Sonsey May 18 '12 at 18:28
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Not sure I am getting you. A jpg is a single frame and doesn't have the ability to put audio track with it. My only idea of what you ay be doing is loading an audio track in Quicktime 7 and attaching a image to it as a poster image and saving it out as a "movie". If you are doing that, then I am not sure.

Regardless compressor is normally fairly reliable in doing conversions. It can be a very powerful way of batching up lots of conversions for different media types and not have issues.

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I do this kind of conversion all the time using Quicktime Pro. It works just fine. So would Compressor. Stick to common frame rates and sample rates for peace of mind on any device.

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Compressor works fine, but we use MPEG Streamclip for all our conversions to mp4. For some reason it has a faster conversion rate with equal quality.

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