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Topic: freeformat- how I can create mp3 @ 384kbps? (Read 2162 times) previous topic - next topic - Topic derived from freeformat at 640 kbp...
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Re: freeformat- how I can create mp3 @ 384kbps?

Reply #25 –
The only way for a stream parser to recognize Free Format properly is to blindly search ahead for the sync word, since there is no other way to detect the length of a packet, other than completely parsing it.
 

Re: freeformat- how I can create mp3 @ 384kbps?

Reply #26 –
Quote from: kode54 on
The only way for a stream parser to recognize Free Format properly is to blindly search ahead for the sync word, since there is no other way to detect the length of a packet, other than completely parsing it.
Theoretically, if we store it in a proper container such as mp4, each frame can be externally delimited on the container side.
Quote from: ajp9 on
ffmpeg recognizes and decodes all of the free format MP3s. Really, player decoders are behind on this. I expected more from MPC-HC.
Well, which version of ffmpeg have you tried?
I just tried with lame --freeformat -b 384, but ffmpeg (version 4.1.4) cannot decode the resulting file.
According to a comment in the libavcodec source (mpegaudio_template.c), they are aware of the free format.
However, when bitrate_index in the frame header is zero, decode_frame() of the decoder just returns an error.
Since this check is in the decoder, ffmpeg won't be able to handle freeformat mp3 even when stored in containers such as mp4.

Re: freeformat- how I can create mp3 @ 384kbps?

Reply #27 –
Huh. I was under the impression that it was ffmpeg under Audacity that loaded free format.

Through process of elimination, and checking the source code, it appears that Audacity's built-in MP3 decoder(s) is handling it.
 
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