MP3 audio in Perian-decoded files exports as silence in QuickTime 7.5

[tylerl]

In QuickTime Player 7.5 (and various other QuickTime framework-using programs, though not all), exporting a file decoded by Perian 1.1 that contains MP3 audio (.avi and .flv containers tested) results in a file with a silent audio track.

Here is a sample .avi file with MPEG-4 video and MP3 audio:  http://homepage.mac.com/tylerl82/test.avi

Steps in QuickTime Player (Pro required): File -> Export... Export format: "Sound to Wave" is the quickest, though "Movie to MPEG-4" and "Movie to QuickTime Movie" also demonstrate the same problem. The resulting file will have a fully-formed audio track, though it will be silent.

The same original file saved/flattened as a QuickTime .mov reacts identically, though strangely enough, iTunes will convert the .mov version with full sound.

[astrange]

Hm, Perian doesn't have an MP3 decoder.

[tylerl]

"MP3 audio track inside container format supported by Perian QuickTime component" is probably a more accurate phrase.

[gbooker]

Sounds like yet another bug in QuickTime. There is nothing different as far as Perian is concerned between playback and export. The only differences are within Quicktime itself.

Try reporting it to them and see what they tell you:  http://bugreport.apple.com

[tylerl]

 rdar://problem/6043662

For what it's worth, with the DivX plugin installed, affected AVI files export with intact audio. For kicks, I made flattened .mov versions of test.avi - one with Perian installed, one with DivX installed. Curiously, after uninstalling DivX and re-installing Perian (or even if neither are installed), the DivX-flattened file will export with intact audio. A similarly-flattened file from while Perian was exclusively installed will not play audio or export audio when only DivX is installed.

 http://homepage.mac.com/tylerl82/testperian.mov  http://homepage.mac.com/tylerl82/testdivx.mov

[tylerl]

...got the standard "not our problem" response from Apple:

This is a follow-up to Bug ID# 6043662.

Engineering has determined that this issue originates with Perian product. Please feel free to contact Perian regarding this issue to help alert them of its importance. (On our test machines with QT 7.4.5 and 7.5 GM which do not have Perian installed, the audio plays fine in QT Player.)

We consider this issue closed. Thank you for taking the time to notify us of this issue.

[gbooker]

Replying to tylerl:

Engineering has determined that this issue originates with Perian product. Please feel free to contact Perian regarding this issue to help alert them of its importance.

Questions for them: Why does it playback, but not export? What could Perian possibly do that affect this difference? Both convert the mp3 in the container to PCM, and then QT handles it from there.

(On our test machines with QT 7.4.5 and 7.5 GM which do not have Perian installed, the audio plays fine in QT Player.)

Gee, that's interesting. I removed Perian on my machine, open the .avi file, and no audio plays! Furthermore, there's no audio there at all!

It would really help if Apple were to document this stuff. Obviously something isn't being done exactly the way they want, so what is it? Tell us and we will be happy to make the change.

[esetleges]

Same story: Perian version: 1.1.3 QT version: 7.6 OS version: 10.5.6

Import: .avi with mp3 audio Export: .mp4 (video decoder apple mpeg4 or xvid or x264) audio: aac or mpeg 4 Delay AAC Bug: silent audio track after export

Audio track works correct with DivX encoder.

[astrange]

On which AVI? And did you mean DivX decoder (which the encoder installs) or did you specifically use the encoder for something?

I forgot to mention that all three files (test.avi, testdivx.mov, testperian.mov) export with sound for me using SVN and no other decoders.

[astrange]

…but the values in perian's audio SampleDescription? are obviously wrong (samplesPerPacket = 1 instead of 1152). bytesPerPacket and bytesPerFrame are different across Perian/DivX/opening the mp3 by itself, so those probably don't matter.

[astrange]

Improved in r1042. Note that this part of QT seems buggy (it copies mFramesPerPacket (576) into the SampleDescription? when it should be 1152).