[FFmpeg-trac] #1848(avcodec:new): AMR-NB Q bit ignored

FFmpeg trac at avcodec.org
Fri Oct 26 14:16:26 CEST 2012

#1848: AMR-NB Q bit ignored
             Reporter:  krisha      |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  amrnb       |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |

Comment (by krisha):

 I can not give you a command line or console output for that. This I saw
 inside the code. And since this variable is not READ anywhere I know that
 it is not used. There is also no output logging for this variable.

 Steps to reproduce in case someone wnats to solve it:
 1. Create a AMRNB file with 12.2 kbps and some seconds of silence
 2. Each frame starts with 0x3C and 32 bytes of data, starting directly
 after header
 3. Modify one 0x3C to 0x38 (Q bit cleared) and add change some random bits
 inside the 32 bytes of data.
 4. watch the waveform or listen to it

 Actually it does not matter if the header is 0x3C or 0x38. The frame will
 be played or displayed anyway with the corrupt data. If I understood the
 RFC right, it should not be played back but just used to improve overall

 If someone wants to fix it, I'm here to explain in detail or to provide

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1848#comment:2>
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