[Ffmpeg-devel] Re: AMR bitrate

[Benjamin Larsson]

Martin skrev:
> Hi,
> 
> gravsten at yahoo.com wrote:
>>>> I have a question regarding encoding and decoding of AMR using
>>>> ffmpeg. To me it seems that the bitrate mode is fixed after
>>>> avcodec_open(). Is that correct (the bitrate mode cannot be changed
>>>> on the fly)?
>>> No the bitrate can't be changed on the fly and user questions
>>> to the user list.
>>
>> Actually, the standard let one negotiation a set of AMR bit rates beforehand,
>> and the transmitter may arbitrarily change bitrate within the agreed set on an
>> AMR frame boundary (20ms).
>>
>> I am unsure whether ffmpeg let you change the bitrate on-the-fly (i.e. without
>> close/open codec), but if not, you should be able to fix this by merely making
>> the AMR codec access a bitrate value in the avctx structure directly (ffmpeg
>> only serves as a proxy to an external AMR library originally from the ITU).
> 
> thanks for clarifying that!
> I tested it and it worked. Would you accept a patch for that? There
> shouldn't be a downside in directly accessing the avctx structure, right?
> 
> Martin

Send the patch for review.

MvH
Benjamin Larsson