[gst-devel] AMR caps incompatibility between muxer and encoder

[Benoit Fouet]

Daniel Díaz wrote:
> Hello there!
>
>
> On 10/25/06, Benoit Fouet <benoit.fouet at purplelabs.com> wrote:
>   
>> Hi
>>
>> SP GLE wrote:
>>     
>>> Hi,
>>> I'm trying to link an 'amrnbenc' element and a 'ffmux_mov',
>>> amrnbenc SRC caps are
>>>    Capabilities:
>>>       audio/AMR
>>>                    rate: 8000
>>>                channels: 1
>>>
>>> ffmux_mov SINK Caps are
>>>       audio/x-amr-nb
>>>                    rate: [ 8000, 96000 ]
>>>                channels: [ 1, 2 ]
>>>
>>> so linking seems incompatible, how can i link these elements ? Is there
>>> a way to change capabilities ?
>>>
>>> failed negotiation between pads is attached for the following cmd :
>>> GST_DEBUG=4 GST_DEBUG_NO_COLOR=1  gst-launch audiotestsrc !
>>> audioconvert ! amrnbenc ! ffmux_mov ! filesink location=/tmp/f.mov
>>>
>>> Thanks.
>>>
>>>       
>> you have to change the source code of amr decoder, so that it is
>> audio/x-amr-nb too on its sink pad.
>>     
>
> Why was that, again?
>
> As I understand it, audio/x-amr-nb-sh is "MIME-ful" AMR narrow band,
> that is, with a header like this: `echo '#!AMR' > header.amr`.
>
> Then, audio/AMR is "MIME-less" AMR information. Certainly, the output
> of the amrnbenc is lacking such header because it is pure AMR data, no
> MIME header.
>
> That's why amrnbparse takes audio/x-amr-nb-sh and outputs audio/AMR.
>
> See section 8.1 of RFC 3267, where it says that MIME type for AMR is
> precisely audio/AMR, with audio/AMR-WB being used for wide band.
>
> Also, I vaguely recall that one of the de/muxers needed such header
> for AMR, or needed it not when coming from RTP. Or something
> in-between :) But in any case, it is possible to have a complete
> pipeline with those elements without changing the source code.
>
> Hope that makes some sense.
>   
that does :)
indeed, I modified a bit the amrnb- dec/enc stuff a bit here, so that it
handles the amr header.
(to avoid the use of the amr parser)
sorry for all the noise, it seems i told a lot of stupid things yesterday...

indeed, thanks for explanation Daniel !

-- Ben

> Daniel Díaz
> ddiaz at ti.com
>
>
>   
>> then compile and install back the library, and this should be ok :)
>>
>> Hope that helps,
>>
>> -- Ben
>>     
>
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