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Hello all,
I have a question regarding how audio in a QuickTime file is read in Compressor. Recently, there has been word that QT files are being rejected from one of our vendors because of "the audio codec identified incorrectly as '32-bit float'".
Now, opening the file in dumpsters shows: 'trak' > 'mdia' > 'minf' > 'stbl' > 'stsd' > dataFormat = in24
A quick search of the QT-Users mailing list provided some insight on in24: "Technically speaking, 'in24' isn't a compressed format, so it requires no audio codec to decompress. It's the old Sound Manager way of specifying 24-bit linear pcm audio. Endianness (big or little endian) is specified as a sound description." - Brad Ford (ni24 audio in mov files - 10/26/09)
Anyway, when I export from QT Pro and use LPCM as the audio codec and select a sample size of 24-bit, then it seems Dumpster shows the following: 'trak' > 'mdia' > 'minf' > 'stbl' > 'stsd' > dataFormat = lpcm
Here is the thing, the only application that they (our vendor) is using to validate the sample size is Compressor, and this is the only application that is displaying in24 as 32-bit float in the Inspector > A/V attributes.
Every other application we are using (Dumpster, QT Pro, MediaInfo Mac, Final Cut Pro) is correctly displaying 24-bit integer as the sample size for audio.
The 32-bit float QT files are being produced by us using FCP. Interestingly enough, Page 324 of the FCP users manual (Choosing Sequence Bit Depth) states that sequence audio is always mixed using 32-bit floating-point values.
We are thinking that Compressor is somehow reading the sample size incorrectly and therefore our vendor is unnecessarily exporting the audio from QT Pro to properly display the sample size in Compressor.
Obviously we have done some extensive testing and find that only Compressor is reporting a 24-bit integer file as 32-bit float.
Finally, our vendor has stressed that only version 3.0x of Compressor is to be used, not 3.5x or for that matter, anything in FCS 3.
Any insight would be greatly appreciated. -- Michael Magallon
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