Hi there. This is working fine for me on Windows 10 (thanks!) but I was hoping there'd be a way to change the bitrate? I'd like to increase it but don't know how.
use arguments with ffmpeg (-ab 192k -ar 44100) to improve the bitrate must do cmd line option instead of gui
aaxtomp3 -i book.aax| ffmpeg -i pipe:0 -ab 192k -ar 44100 "book.mp3"
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Cool thank you, I have created a simple batch script and added it to my 'Sent To' folder - I can just right click an audioable book and choose to convert it at higher rate.
Hey guys.
I am also concerned about the bitrate. But I think, what you're doing is a workaround with a pretty strong disadvantage:
All aax files I have are encoded with 64kbit/s (simply calculated by filesize/runtime). So in thereoy reencoding these files with 64kbit/s aac should result in the best quality possible.
If you're converting the files to 192kbit/s mp3, you'll still have 64kbit/s woth of data in a file, which is three times as big as it should be. So you'll end up with a file, which is 2/3 nothing but data waste.
Still, I understand your problem:
If you convert an aax file to 64kbit aac, it sounds not nearly as good, as it should.
The question is: why?
If my information is correct, AAX is nothing but encrypted AAC, so converting to aac should result in no quality loss. But for some reason, it does.
Id did some experiments using WinRAR:
First I encodede the same AAX file (actually only one chapter) to different bitrates using the AAX2MP3 converter. Then I put them into a WinRAR archive. This way I could determine, how much "redundant" information the files contain.
The results can be seen in the attachment (2nd column is the unpacked file size, 3rd column is the packed file size using WinRAR and "best" compression).
If you go from 64kbit to 128kbit, you nearly double the file size, but only get 70% more of real information. If you go higher, it get's even worse. Above ~200kbit, you'll get no more information out.
There should be a way to convert the file "bit perfect", so exactly the same amout of information with the exact same filesize. Can someone with more knowledge of audio encoding pls jump in and tell us, either how to achieve that or why it is not possible?
PLEASE!
All files I have (wether they are called "Audible AAX" or "Audible enhanced audio") do have a data rate of pretty precisely 64kbit (filesize times 8 divided by runtime in sec).
Are you suggesting they are encoding 128kbit or even 192kbit audio to a data rate of only 64kbit?
In that case I'd like to know what encoder they are using to get that sort of compression without quality losses.
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I am suggesting nothing. I havent looked at a file or performed a calculation.
I simply read documentation which stated format 4 was supposed to be 64kpb and enhanced was supposed to be 128kpb or higher. simply having documentation neither implies it is neither current nor accurate.
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After talking with some other ppl, who are more familiar with audio encoding, I am sure it is just about the encoder.
The encoder in the ffmpeg.exe ist just not the best one, especially not for MPEG4/AAC.
When converting to AAC, you should use twice the input bitrate as output bitrate.
The MP3 encoder however is much better. But still at 64kbit, its pretty bad. For me MP3 and 128kbit/s ist die best solution, granted the Input file has 128kbit or less. In that case I can't hear the slightest difference between a file encoded with 128kbit and a file encodede with higher bitrate (192-320kbit). I am using an Asus Xonar STX soundcard either on AKG headphones or on my HiFi System and still there is simply no difference hearable.
So my advice:
If the AAX file is 64kbit or 128kbit --> go for MP3 and 128kbit
If the AAX file is 192kbit --> go for MP3 and 192kbit
(To find out, what bitrate you AAX file is: just divide the Filesize by runtime in seconds and multiply by 8)
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I am wondering about this as well, the bitrate quality is rather low - any way to increase it or is this limitation of audible ?
use arguments with ffmpeg (-ab 192k -ar 44100) to improve the bitrate
must do cmd line option instead of gui
aaxtomp3 -i book.aax| ffmpeg -i pipe:0 -ab 192k -ar 44100 "book.mp3"
Cool thank you, I have created a simple batch script and added it to my 'Sent To' folder - I can just right click an audioable book and choose to convert it at higher rate.
AxxToMp3 (192k bitrate).bat
Thanks for the 'Send To' idea. Works great.
Here is a sample bat file you could use to do a whole directory (e.g batfile.bat *.aax)
FOR /f %%a in ('dir /b *.aax') DO (AaxToMp3.exe -i %%~nxa | ffmpeg.exe -i pipe:0 -ab 64k -ar 44100 %%~na.mp3)
Last edit: M A 2016-01-03
Hey guys.
I am also concerned about the bitrate. But I think, what you're doing is a workaround with a pretty strong disadvantage:
All aax files I have are encoded with 64kbit/s (simply calculated by filesize/runtime). So in thereoy reencoding these files with 64kbit/s aac should result in the best quality possible.
If you're converting the files to 192kbit/s mp3, you'll still have 64kbit/s woth of data in a file, which is three times as big as it should be. So you'll end up with a file, which is 2/3 nothing but data waste.
Still, I understand your problem:
If you convert an aax file to 64kbit aac, it sounds not nearly as good, as it should.
The question is: why?
If my information is correct, AAX is nothing but encrypted AAC, so converting to aac should result in no quality loss. But for some reason, it does.
Id did some experiments using WinRAR:
First I encodede the same AAX file (actually only one chapter) to different bitrates using the AAX2MP3 converter. Then I put them into a WinRAR archive. This way I could determine, how much "redundant" information the files contain.
The results can be seen in the attachment (2nd column is the unpacked file size, 3rd column is the packed file size using WinRAR and "best" compression).
If you go from 64kbit to 128kbit, you nearly double the file size, but only get 70% more of real information. If you go higher, it get's even worse. Above ~200kbit, you'll get no more information out.
There should be a way to convert the file "bit perfect", so exactly the same amout of information with the exact same filesize. Can someone with more knowledge of audio encoding pls jump in and tell us, either how to achieve that or why it is not possible?
PLEASE!
Last edit: Stefan Erkens 2015-11-15
from the documentation I read, as long as you are using enhanced files they are either 128kb or 192kb and 44.10kHz
Last edit: scott obrien 2015-11-16
All files I have (wether they are called "Audible AAX" or "Audible enhanced audio") do have a data rate of pretty precisely 64kbit (filesize times 8 divided by runtime in sec).
Are you suggesting they are encoding 128kbit or even 192kbit audio to a data rate of only 64kbit?
In that case I'd like to know what encoder they are using to get that sort of compression without quality losses.
I am suggesting nothing. I havent looked at a file or performed a calculation.
I simply read documentation which stated format 4 was supposed to be 64kpb and enhanced was supposed to be 128kpb or higher. simply having documentation neither implies it is neither current nor accurate.
After talking with some other ppl, who are more familiar with audio encoding, I am sure it is just about the encoder.
The encoder in the ffmpeg.exe ist just not the best one, especially not for MPEG4/AAC.
When converting to AAC, you should use twice the input bitrate as output bitrate.
The MP3 encoder however is much better. But still at 64kbit, its pretty bad. For me MP3 and 128kbit/s ist die best solution, granted the Input file has 128kbit or less. In that case I can't hear the slightest difference between a file encoded with 128kbit and a file encodede with higher bitrate (192-320kbit). I am using an Asus Xonar STX soundcard either on AKG headphones or on my HiFi System and still there is simply no difference hearable.
So my advice:
If the AAX file is 64kbit or 128kbit --> go for MP3 and 128kbit
If the AAX file is 192kbit --> go for MP3 and 192kbit
(To find out, what bitrate you AAX file is: just divide the Filesize by runtime in seconds and multiply by 8)
How did you encode into aac?
How did you guys get this to work in Win10? Mine's in Dutch or asks for a dll I don't have.