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

Måns Rullgård mru
Wed Nov 15 23:30:25 CET 2006


Stefan Gehrer <stefan.gehrer at gmx.de> writes:

> 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 have a few hardware decoders I might try on those files.

> 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.

Did you look for Lame signatures?  Sometimes they are quite obvious.

-- 
M?ns Rullg?rd
mru at inprovide.com




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