[Freeswitch-dev] Questions on implementing mod_nelly codec

[Richard Alam]

Yes, we plan on contributing the module once it's working.

On Tue, Mar 22, 2011 at 5:19 PM, Anthony Minessale
<anthony.minessale at gmail.com> wrote:
> Are you planning to contribute this module?
>
> On Mon, Mar 21, 2011 at 1:58 PM, Richard Alam <ritzalam at gmail.com> wrote:
>> Hi,
>>
>> We've been trying to implement a mod_nelly codec but so far has been
>> unsuccessful. We use a Nellymoser compatible codec submitted to ffmpeg
>> (see June 16, 2008 entry of http://ffmpeg.org/).
>>
>> Our plan is to use Flash using Nellymoser to connect to a conference
>> in FreeSWITCH.
>>
>> The hurdle seems to be that Nellymoser decodes 64 byte nelly audio to
>> 512 byte L16. Nellymoser is 11-Khz 8-bit per sample with 32 ptime.
>> However, L16 implementations are all 20 ptime
>> which have uncompressed bytes in multiples of 320. This doesn't align
>> with what mod_nelly expects when encoding (convert 512 bytes to 64
>> bytes) and decoding (64 bytes to 512 bytes).
>>
>> Here is the SWITCH_MODULE_LOAD_FUNCTION(mod_nelly_load)
>> [http://pastebin.freeswitch.org/15764] now. We've played around with
>> the samples per second (SPS), actual samples per second (ASPS),
>> bits per second (BPS), and the ptime (PTIME) but with no luck. It's
>> either we get bad very choppy audio, incompatible destination (when
>> codecs can't match), or no audio at all. We've managed to get the
>> "You will now be placed into the conference" audio played correctly
>> but the audio from the caller is bad. Just the paying of wav file from
>> FS is correct.
>>
>> My question is how does transcoding works in FS? Am I correct to
>> assume decoding as Nelly->L16 and encoding as L16->Nelly?
>> So basically the media flow for our use case is Nelly -> L16 -->
>> mod_conference -> L16 -> Nelly.
>>
>> Do I need to make the frames align? In this case, Nelly expect 256
>> samples per frame while L16 has 160, 320, ... samples per frame.
>>
>> Hope I've articulated clearly what we are trying to accomplish.
>>
>> Suggestions and ideas on what to try out next is much appreciated.
>>
>> Thanks in advance.
>>
>> Richard
>>
>>
>> --
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>
>
>
> --
> Anthony Minessale II
>
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