File Size Limit for m4b?

[Nick Goddard]

I'm trying to convert m4b files 500 minutes plus long to mp3. The result works fine but is only the first hour or so of the original. Any ideas how to fix this??

[LtData]

What size is your .m4b file?

[Spoon]

And what frequency and channels?

[ChristinaS]

A 500 minute audio file will need about 5GB of space for the uncompressed 16-bit PCM wav file I assume is created internally before compression to mp3 actually can take place (10MB per minute). That's assuming 2 channel stereo. Half of that space would be needed for mono.

I'd say you need a lot of ram to do this and a lot of temporary disk space, if it is even meant to work at all. Plus some good processor speed.


That is just my own gut feeling.

Spoon can confirm if an interim wav file is actually created for the entire audio before compression takes place, or not.

If not, then, well, I'm wrong :o

[Spoon]

If using mp3 (Lame) there should be no temp file (assuming no DSP effects).

[Nick Goddard]

The files are around 300Mb, frequency 44100, 2 channels, 64Kbps. Is ther any way to break them into smaller chunks for processing? :(

[Spoon]

There is a splitter utility codec in Codec Central, if the problem lies with reading the m4b file then that will not help either.

[ChristinaS]

Nick, did you try a test Conversion first? It will only analyse the inout file and not actually oerform the conversin at all. If that doesnt work, then you cannot convert the file.

If the .m4b file is protected you cannot convert it. I don't know if the protection it may have woudl have allowed it to work partway as it first did for you though.

If it is protected then you can record it using dMC Auxiliary Input - in real time. It will be a long night.

For the mp3 - what settings had you picked? There's no benefit in picking a higher bitrate than what you start out with, only getting a bigger output file. if using presets you may be using somehtign resulting in higher bitrates, so take a look at what you have.

And as Spoon said, check for DSP effects. They may have been forgotten from some prior conversion or may even be present there from some installation default.

[Nick Goddard]

Trying conversion alone, each file would still stop at the same place regardless of the settings I chose. After some hardware rigging, I have taken Christina's advice and used DMC auxilary input to do the job overnight. I works!

Thanks for the help Christina and Spoon.

[jaminbenjamin]

I am having the exact same problem. I am trying to convert m4b files (around 200-400mb each) into mp3's. Whenever I try to do this, a 242mb 500min m4b file will end up being a 164mb 70min mp3 file.

After trying several different files, they all stop at around the 70min mark. I suspect that the program has problems converting to an mp3 file that is extremely large (bigger than 70min or ~160mb).

Besides trying the Auxilliary input solution, anyone have an easy way to break up m4b files into smaller parts?

[jaminbenjamin]

Sorry, had trouble editing my last post so had to start a new one...

After more investigation, it seems like m4b files have some type of chapter or similar markers. In the particular files that I am trying to work on, these markers happen where one CD would normally end and the next CD begins (whoever created the m4b files combined many CDs into one file). It seems that the converter stops converting whenever it gets to this spot, isntead of continuing until the end of the file.

The only reason I am making any kind of deal out of this is because I actually forked over some money for the program/utility and came across an obvious flaw that will hopefully be remedied.

[ChristinaS]

Oh, this is a bookmarkable file. Audible book!

I found some references on the web that renaming the file to m4a (or perhaps m4p) "may" remove the bookmarks.

I don't know why that should be so and quite possibly this does not work.

But from some past discusison on audible books, it seems yuo can play the file in some player (WMP ???) and "rewind" it so it will remove the bookmark.