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Topic: Possible to convert MPEG2 AAC to MPEG4 AAC (Read 11880 times) previous topic - next topic
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Possible to convert MPEG2 AAC to MPEG4 AAC

I'd like to take a collection of MPEG2 LC-AAC files and convert them to MPEG4 LC-AAC files before wrapping them in an MP4 container.  My understanding is that the difference is a bit more header info on the MPEG4 AAC, so I was hoping to use something like MP4Box to losslessly pack them into an MP4 container for compatibility with my iPod, rather than transcoding.

Unfortunately, iPods can't play MPEG2 and packing the MPEG2 AAC file using MP4Box didn't magically make the whole thing an MPEG4 stream as I had hoped.

Has anyone else had any luck doing this?  What tools did you use?

Thanks!

EDIT:  I should add, I've tried to use aacpatch and received the error: "Failed (sync bits not found)...exiting!"

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #1 –
Unless I'm completely misunderstanding your question, I don't know if it's possible to do that at all.

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #2 –
I tried searching around and couldn't come up with anything.  I don't know if mpeg-2 AAC works in the same way as mpeg-4 AAC.  With mpeg-4 AAC, you can extract the raw AAC audio out of the mpeg-4 container and do whatever you want with it.  I don't know if mpeg-2 AAC works the same way or not.  They are different audio formats though, header info is the tip of the iceberg in terms of how different mpeg-4 and mpeg-2 are.

I just don't think mpeg-2 AAC works the same way as mpeg-4 AAC.  I see no reason why it wouldn't but then again, I am not an expert on the mpeg-2 audio format.

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #3 –
There's a tool on RareWares' AAC section called "Nic's AAC patch" that "Converts MPEG2 AAC files to MPEG4 AAC files, and vice versa."

here's the linky (scroll to the bottom)
we was young an' full of beans

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #4 –
Quote from: skelly831 on
There's a tool on RareWares' AAC section called "Nic's AAC patch" that "Converts MPEG2 AAC files to MPEG4 AAC files, and vice versa."

here's the linky (scroll to the bottom)


Yeah, that app is what originally got my hopes up after I read this post: HERE

Unfortunately, when I run that I get the error message: "Failed (sync bits not found)...exiting!"  I'm not sure what it's looking for there, and several prayers to google yielded no light.  It looks like others are seeing the same error message, but I haven't read a description of what's going on or any possible solutions.

Thanks!

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #5 –
Quote from: octbit on
Quote from: skelly831 on

There's a tool on RareWares' AAC section called "Nic's AAC patch" that "Converts MPEG2 AAC files to MPEG4 AAC files, and vice versa."

here's the linky (scroll to the bottom)


Yeah, that app is what originally got my hopes up after I read this post: HERE

Unfortunately, when I run that I get the error message: "Failed (sync bits not found)...exiting!"  I'm not sure what it's looking for there, and several prayers to google yielded no light.  It looks like others are seeing the same error message, but I haven't read a description of what's going on or any possible solutions.

Thanks!


The tool is probably expecting ADTS AAC headers, instead of raw AAC files.

As far as I know, if you manage to convert the files to raw AAC, then there is no difference between MPEG2 and MPEG4 from the aspect of the player.




Quote from: kornchild2002 on
They are different audio formats though, header info is the tip of the iceberg in terms of how different mpeg-4 and mpeg-2 are.


The only difference in LC-AAC is that MPEG-4 LC-AAC can contain PNS and MPEG-2 LC-AAC can not. The ADTS headers have a bit to signal which one it is.

Note that the iPod does not properly support PNS, so it supports MPEG-2 LC-AAC only, not MPEG-4, but it needs it's MPEG-2 LC-AAC signalled as MPEG-4 LC-AAC. Lovely, isn't it?

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #6 –
@octbit: try the last MP4Box build...

Code: [Select]
MP4Box -add input.aac:mpeg4 output.m4a

Possible to convert MPEG2 AAC to MPEG4 AAC

Reply #8 –
This is ridiculously simple! I had an ADTS AAC and wanted to be able to play it on my iPhone. MP4Box did the job so smoothly! Thank you!