[Ffmpeg-devel] [BUG] garbled sound when playing 8kHz MP3s

Stefan Gehrer stefan.gehrer
Wed Nov 15 23:11:12 CET 2006


Michael Niedermayer wrote:
> Hi
>
> On Wed, Nov 15, 2006 at 10:10:15PM +0100, Stefan Gehrer wrote:
>   
>> Hi list,
>>
>> I found that 8kHz mp3 files sound a bit garbled when decoded with ffmpeg.
>> I also get error messages like
>>
>> foo at bar:~$ ./ffplay ../s8000.mp3
>> invalid new backstep 95
>> overread, skip -7 enddists: -1 -1
>> overread, skip -7 enddists: -5 -5
>> overread, skip -7 enddists: -1 -1
>> overread, skip -6 enddists: -4 -4
>> invalid new backstep 130
>> overread, skip -6 enddists: -1 -1
>> overread, skip -7 enddists: -6 -6
>> overread, skip -9 enddists: -7 -7
>>
>> The same happens when playing back in mplayer or mpg123, but the error 
>> message are different:
>>
>> mpg123: Can't rewind stream by 5 bits!1%
>> mpg123: Can't rewind stream by 144 bits!
>> mpg123: Can't rewind stream by 3 bits!1%
>> mpg123: Can't rewind stream by 22 bits!%
>> mpg123: Can't rewind stream by 46 bits!%
>>
>> But if I decode the file with lame, it sounds OK.
>> To reproduce, it should be sufficient to encode your favorite piece of music
>> with 'lame --resample 8' (note that this is not a general recommendation to
>> encode good music at 8kHz :) ).
>> But if anybody is interested I can upload a sample where this happens.
>>     
>
> is there any decoder besides lame which can decode it? if no then i would
> guess that the bug is in lame though thats just a guess (1 buggy program vs.
> 2 buggy programs)
>
> [...]
>   
Actually yes, there is. It is just not publicly available. But I 
recently had to test
an embedded decoder solution and compared it with open source decoders.
The decoder under test and lame succeeded, ffplay/mplayer/mpg123 failed
on the (lame-encoded) 8kHz sample. And I can assure you that the decoder
under test did not have any code common with lame.
I also came across this recently with a file from the Internet, I will 
see if I can
dig out a link. Of course I would not know if this was lame-encoded or not.

Regards
Stefan Gehrer




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