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Topic: .MP4 / .M4A files problem... please help (Read 3299 times) previous topic - next topic
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.MP4 / .M4A files problem... please help

Hello!

I need your advice in the following thing. I have MANY .MP4 files encoded in the following way:
1) encoded by PSYtel with the parameter "-profile 0" (LC profile)
2) converted into .MP3 using: mp4creator -aac-old-file-format -create="in.aac" out.mp4

QuickTime "understands" such files, but there is a problems with iMac/iTunes 4.xx.
It recognises the .mp4 file as "QuickTime movie", not as "AAC Audio file".

Here a message I got from one man:
"I cannot add the album picture until the songs are recognised as AAC. This is funny actually, it is enough to rename the file(s) as .m4a - and it is AAC imediately. Interesting thing: the files hasn't got the datarate of 192kbps, as downloaded, but it writes that it is 187kbps. BUT, iTunes crashes when calculating the sound volume! So I use to take the song in .mp4, copy it to iTunes music library on my hard disk, CONVERT IT TO AAC (converting the selected songs takes as much time as grabbing of AudioCD!!!) and then it is done. The costs of the time is one thing, but I am not satisfied WITH THE CONVERSION, I mean I have to convert compressed file?! I do believe there is a quality loss."

Do you have any advices? How to create a real .M4A files using PSYTel?
Is there any other way to create ".M4A" files from COMMAND LINE? (I use PSYTEL because it is a command line utility).

Thank you.

.MP4 / .M4A files problem... please help

Reply #1
For apple iTunes, the file extension on its MPEG 4 files, are either M4A or M4P. The container difference between an .MP4 extension for the filename created by MP4Creator are no different to the container used by Apple. An MPEG 4 container, is an MPEG 4 Container, if you wish to extract the AAC, or which ever stream inside the MPEG 4 Container, be it an MP4, M4A or whatever, you can also use MP4Creator to extract the tracks. This does not recompress the file, due to the fact that an MPEG 4 Container actually "contains" the AAC bitstream. or WAV file or MP3 file etc.

Simply renaming the files to M4A are sufficient, as iTunes does not accept the MP4 file extension (as yet?)

The difference between 187kbps and 192kbps, is due to the fact that the bit reservior for the pystel encoder, will not always get identical to the 192kbps, its an average bitrate, the 187kbps, is more likely the real bit rate. 192kbps is purely an estimate.

Simply using "ren *.mp4 *.m4a" will change your files from MP4's to M4A's so iTunes will recognise...

Using the latest beta's of Foobar 2000, will also let you tag the mp4 files to the tagging used by iTunes and hence iPod's, making the differences between the implementation of the MPEG 4 Containers even less (bitwise)

Ciao