[FFmpeg-user] MP4s (and M4As) for music

[Mark Filipak]

On 08/06/2025 13.51, Paul B Mahol wrote:
> On Sun, Jun 8, 2025 at 5:42 PM Mark Filipak <
> markfilipak.imdb-at-gmail.com at ffmpeg.org> wrote:
> 
>> ffmpeg^
>>    -i "c:\chapters.txt"^
>>    -i c:\01.WAV^
>>    -i c:\02.WAV^
>>    -i c:\03.WAV^
>>    -i c:\04.WAV^
>>    -i c:\05.WAV^
>>    -i c:\06.WAV^
>>    -i c:\07.WAV^
>>    -i c:\08.WAV^
>>    -filter_complex
>> "[1:0][2:0][3:0][4:0][5:0][6:0][7:0][8:0]concat=n=8:v=0:a=1[out]"^
>>    -map_metadata 0 -map "[out]"^
>>    -c aac -b:a 657.6k^
>>    "c:\Ashra, Belle Alliance [1980].m4a"
>>
>>
>> *****
>> The script above provoked this: "Too many bits 15269.442177 > 12288 per
>> frame requested, clamping to
>> max". Of course, I have no idea what that's about. Do you? "Too many bits"?
>> *****
>>
>> How did FFmpeg (or AAC) compute "15269.442177 > 12288". What are those
>> numbers? Why does the
>> complaint say "bits ... per frame requested" when there's _no_video_,
>> _no_frames_?
>>
> 
> https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/aacenc.c#L1243

Thank you, but I can't read that. Is there documentation in English?

Can you tell me why FFmpeg (or AAC) says "15269.442177" when I submitted "-b:a 657.6k"?